Cornell University

Library

OF THE

Hew Work State College of Agriculture

 

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1820

 
SB 624.03S4

ii
BULLETIN

OF THE

Ohio Agricultural Experiment Station

NoumsBer 214 ‘Marcu, 1910.

 

 

A BRIEF HANDBOOK OF THE DISEASES OF
, CULTIVATED PLANTS IN OHIO

By A. D. SELBY

INTRODUCTION

The idea of disease is not a simple one, though it may seem so
before trying to define it. In reality the term “‘disease’’ as applied
to plants, means any change in that plant toward reduced vigor, etc.,
from the ordinary or average behavior. To put it another way, a
plant is said to be ‘‘diseased’”’ when it shows any deviation from the
ordinary or average behavior of that plant in respect to appearance,
growth, color of bark, foliage, fruitfulness, time of dropping leaves
or length of life; in short, when the plant fails to conform to those
averages which we have established by extended observation for
the species and variety in question, we say it is diseased. Under
such a general definition, variegated or purple hued sports would
be included, although potentially rather than actually in diminished

-vigor. Variegated sports succumb easily to parasitic attack and, as
later investigations show, are really suffering from enzymatic
troubles.

The more usual symptoms of disease are marked by evident
differences in the plant. The leaves become spotted, curled or
discolored, or may even drop prematurely; the fruit may develop
unevenly or be marked by decayed spots, or the twigs may blight,
wilt or die. In all such cases we have a manifest loss of vigor and
reduced profit. Yet we may not attribute all these to parasitic
fungi or to parasitic insects; purely physical or chemical agencies
may be at the bottom of certain troubles. Plants may be as-
phyxiated by too much water which excludes the air supply; they
may likewise, be strangled by escaping gases, especially in the case
of city shade trees, or their protoplasm may be attacked by chemi-

(307)
vy
308 OHIO EXPERIMENT STATION: BULLETIN 214

cal agents such as strong acids and alkalis. Quick growing plants
appear to fall in drought, as with cucumbers when started during
a period of excessive rains. Plants, and especially trees, may be
locally injured by winter freezing, by hail, by overbearing with ex-
haustion of water supply, and by a variety of causes.

While we must keep our minds open to these varying causes of
impaired vigor, by far the larger number of the diseases described
in this bulletin are directly attributable to parasitic fungi which
attack the plant or host in some vital part and rob it of its substance.
The conditions of injury arising from the attacks of insects alone
are not included. These fungus parasites of particular plants are of
differing sorts, which produce, each, its more or less particular
effects. It must follow, therefore, that the diseases produced
differ in nature and that the names applied will vary accordingly.
The names are not simply blight, rust, etc., indiscriminately
applied—they are given with reference both to the parasite and its
effect on the host plant.*

Parasitic fungi and bacteria which cause disease, being plants,
though of lower class, have differences among themselves which may
be clearly designated and defined. ‘The names applied to them are
accompanied by specific and generic descriptions which mark off
the sort as definitely as do the descriptions on higher plants such
as ferns, flowering plants and trees. The extreme minuteness of
the parts of parasitic fungi and bacteria make necessary the use of
the microscope in their description and detection. ‘The parts called
spores which reproduce these minute plants have special form, size,
etc., by which these are recognized when found.

The agencies for the spread of parasitic diseases are those
operations in which we engage or those which surround and envelop
the plantsas well as ourselves. Light spores will be carried by
currents of air like particles of dust. Allspores or germs of these
lower plants may be carried by numerous agencies such as insects,
higher animals, and man. They willalso find entrance into plants
by whatever openings exist at the time. The epidermis of a green leaf
or stem has breathing pores or stomates init; the leaves of mustard
plants have water pores in them and wounded plants have these
freshopenings to invite the entrance of the disease conveying
spores or germs.

The remedies for plant diseases are based upon the character
and life history of the particular parasitic growth with which we
have to deal and upon the nature of the host plant itself—some
hosts being very different from others in respect to permitting of

sprays of fungicides or insecticides. Common sense inferences are
* See naming of diseases.
DISEASES OF CULTIVATED PLANTS 309

always of use in dealing with plant diseases. If the soil is too wet,
drain it; if late growth predisposes to winter injury, avoid such
growth; if overbearing weakens plants, prevent, it by thinning
the fruit.

The philosophy of seed treatments is stated under diseases
which infest the seed; that of soil treatments or disinfection, under
soil infesting disease, and the general doctrines of sprays, fungi-
cides, etc., under that heading further on. The progress made in
plant disease prevention throughout the world during the period of
about 26 years which has elapsed since the discovery of Bordeaux
mixture in France shows how well adapted that discovery was to
the needs of the times.

The progress made in recent years in the study and control of
plant diseases has been made possible by the agencies recently
developed in the United States in the Agricultural Colleges, the
Agricultural Experiment Stations and the United States Depart-
ment of Agriculture. Itis not expected that this advance in our
knowledge of the diseases of plants or of the methods of disease
control will soon wane. Efforts like the present one to present
briefly the doctrines of disease and the philosophy of disease con-
trol together with brief descriptions of prevailing diseases in our
state, have for their purpose the wider dissemination of the body of
present day knowledge int’ ¢ lines. Such a statement will not
close the march of progr nor make less the need for more
knowledge. Itis hopedt ‘cultivators of plants, whether farmers,
gardeners, horticulturists or florists will find suggestive statements
of information in the bulletin by which they can direct their own
efforts to better advantage and correct or broaden their own in-
ferences from observed conditions about them. All such results
will not only increase the need for more knowledge, but will furnish
impetus to the movements by which we will gain the desired
information.

In the preparation of the revised edition of the original Bulletin,
No. 121, the general part immediately following this introduction
has been considerably enlarged and brief discussions are now given
concerning groups of plant diseases as well as those concerning
parasitic fungi. It is fully apprehended that the host plant is the
center of practical as well as economic interest and these statements
concerning enzymatic diseases as in the case of peach yellows and
mosaic disease of tobacco, diseases transmitted in the seed, soil
infesting diseases, and the relation of the spread of certain diseases
to leaf biting insects are given as aids in mastering the principles
involved. ‘The same aim has governed the discussions upon wounds
310 OHIO EXPERIMENT STATION: BULLETIN 214

and wound fungi so especially dangerous with orchard, shade and
forest trees. Somewhat fuller discussion of atmospheric agencies
as affecting the occurrence and spread of plant diseases, of
remedies for diseased conditions and of the application of the latter
in combatting diseases and a presentation of storage troubles has
also seemed desirable. Special attention is called tothe host plant
in the matter of breeding or selection for disease resistance and in
the contrasts offered by American and European points of view in
plant disease study.

ACKNOWLEDGMENTS

The illustrations in this bulletin have been drawn from wider
sources than in the previous hand book. A large number, including
perhaps, a larger portion of the cuts, are taken from previous pub-
lications of this Station by Weed, Miss Detmers, and the writer;
small cuts have been at times made from certain larger illustrations
while with others only portions of the original cut have been used.

A great many of the illustrations are new, and I am deeply in-
debted to Messrs. J. M. Van Hook and Thos. F. Manns for many of
the photographs from which these have been made. I am also -in-
debted to Professors Halsted of New Brunswick, N. J., and Atkin-
son of Ithaca, N. Y., and to the Bureau of Plant Industry of the U.S.
Department of Agriculture for many favors in the matter of cuts
which are used in the Bulletin. Figures 24, 25, and 26 are from
Dr. Freeman’s ‘‘Minnesota Plant Diseases.” For permission to
reproduce these, I am indebted to Prof. Frederick E. Clements, of
‘the University of Minnesota. In all cases where it is not otherwise
obvious, it has been the aim to state the source of the illustrations in
the ‘descriptions. The same applies to illustrations reproduced
from standard works.

In many matters connected with recent investigations of the
Department bearing upon diseases included in this present bulletin,
and upon current examinations, I am under many obligations to
Thos. F. Manns, Assistant Botanist, who has rendered very great
assistance.
GENERAL PART I

CONCERNING PLANT DISEASES IN GENERAL

As defined in the introduction, a plant is called diseased when
it fails to show normal vigor and normal condition of its parts.
‘The manner of disease attack is extremely varied and the conditions
set up as a result of disease are accordingly of many different kinds.
We learn to recognize disease by the symptoms shown in the plant;
these symptoms will at times be readily interpreted and on other
occasions they will prove misleading. Nothing is plainer than the
necessity for continuous observation of growing plants if one is to
be in a position to interpret the symptoms of disease.

 

 

 

 

 

Fig. 1. Rootsof white burley tobacco plant attacked by broom-rape. Each of these masses
attached to the root shows beginning of the plant which will grow upin larger dense form, and pro-
duce an abundance of blossoms and seeds but no leaves. Each one of these must have started from a
buried seed of the broom-rape, Orobanche Ludoviciana Nutt.

Diseased conditions may be due tothe very obvious attacks of
certain parasitic seed plants which lack leaf-green or chlorophyll'in
their tissues and must subsist on other plants somewhat after the
manner of parasitic fungi. ‘The dodders which attack the clovers,
alfalfa, onions, etc., belong in the class of parasitic seed plants of
the genus Cuscuta. Their seeds are liable to be harvested with the

‘ (311)
312 OHIO EXPERIMENT STATION: BULLETIN 214

seeds of clover or alfalfa and to be present in the commercial seeds.
While these have been treated in the weed manual they require
mention here. The seedling plant of dodder first forms a
root and sends upward a whitish stem which twines about the
clover or other stem, and sends sucking branches into the stem
interior. ‘These “‘haustoria’ extract food material from the clover
stem—that is they rob it of its own substance. Upon the formation
of such organs the root of the dodder dies off and the future ex-
istence of these twining, strawlike stems is at the expense of the
host plant.

A similar state of parasitic existence is found in the broomrape
tribe whose very small seeds are scattered through the soil. Such
a broomrape is well known on hemp, and the same hemp broomrape
also attacks tobacco in Kentucky and possibly in our state. We
have found another broomrape attacking tobacco in one district of
Brown county, Ohio, and the illustration shows its appearance on
the tobacco roots.

When the leaves of a plant are attacked these show the direct
effects; the symptoms of parasitic leaf diseases are usually localized
injury resulting in spotting and often in browning of the leaf parts.
Leaves may dry up somewhat slowly and drop to the earth, and yet
the leaf tissues are simply dried up. Such conditions may result
from late frost as upon shade, fruit, or ornamental trees. A most
interesting case was once studied upon catalpa as a result of a frost
in May. In that case the drying up was none the less to be expected
at that time.

An even more interesting case of leaf drying and dropping was
upon young catalpa trees ina nursery caused by the attacks of a
root-rot fungus, 7hzelavia. Owing to the death of many of the
rootlets and finer roots as a result of the root-rot trouble, the leaves
of these young trees dried up prematurely in August and Septem-
ber and the leaves all dropped off. Thus we may have leaf
dropping as a result of frost, injury by hail, nor impairment
or localized parasitic attack.

LEAF SPOT AND SHOT-HOLE EFFECTS

Leaf-spot symptoms are everywhere abundant and are really
of very diverse origin. In any example in which the leaf tissues are
locally invaded by a parasitic fungus we may expect evident effects.
In the downy mildew troubles there may be wet-rot symptoms
when the weather is moist, as in the case of Phytophthora or late
blight attacking potato or tomato leaves; after the leaves have be-
come badly diseased they may appear to die very suddenly because
DISEASES OF CULTIVATED PLANTS

the gradual invasion of the areas has been overlooked. In many
other leaf diseases no such rapid multiplication or reproduction of
the parasite is possible and limited dead patches or spots are the
result. The leaf-spot disease of alfalfa, the various leaf-spots of
apple and the conspicuous leaf-spot of the strawberry, the beet,
the pea, etc., will be recalled. In these while the leaves are im-
paired as to usefulness they do not perish immediately and one may
readily fail to estimate the injury at its real seriousness. In a few
leaf troubles we have the spotting of the leaf followed by the for-
mation of a separation layer in the leaf tissues between the para-
sitized and the healthy tissues. This results in ‘“‘shot holes” in
the leaves as is so very conspicuous in the shot-hole leaf disease of
the plum and less conspicuously so on certain sour cherry. trees.
These leaf troubles are commonly very evident during rainy seasons
and are preventable by spraying the foliage of the diseased plants
at repeated intervals, thus keeping a supply of the fungicide on the
leaves to arrest renewed spore development.

An interesting leaf-spot disease of the tomato is sometimes very
damaging. This disease seems to have appeared in Ohio during
the memory of many close observers. Like most leaf-spot troubles
which are strictly due to parasitic fungi, this tomato disease has
been worst in seasons of abundant rainfall. The same applies to
the shot-hole disease of the plum and the allied leaf-spot of cherry.
The explanation appears to lie in more favorable conditions for
spore germination and for the growth or spread of the parasitic
organisms which produce the diseased conditions. Biting or sucking
insects also open the way for the entrance of parasitic diseases,
(See later pages.)

LEAF IMPAIRMENT THROUGH FUNGUS COVERINGS

In addition to the leaf-spots or dead areas in leaves to which
reference has just been made, we have most noticeable examples
of the spread of the mycelium of certain powdery mildews over the
leaf surfaces. Casual observers note that these spread over the
leaves and stems of roses, over the leaves of lilac, of oak, of peach,
of grape, of forcinghouse cucumbers, of bean and pea and upon
other plants. While the development of these fungi or powdery
mildews occurs often rather late in the season, they are nevertheless
damaging to the host plant over which they spread. Above and
beyond the interference with the leaf action the impairment of the
photosynthetic or sunlight processes of the leaves of the plants by
which all real increase in substance is made to the plants, these
mildews develop sucking or penetrating organs of the threads of
314 OHIO EXPERIMENT STATION: BULLETIN 214

the mycelium. These organs called haustoria penetrate the leaf
epidermis and must do this for the purpose of food extraction—it is
needless to add that all food extraction from the plant acts as
robbery. f

Furthermore, the mildew-covered leaves drop to the ground in
fall and there afford the fungus the ‘needed conditions for the
development of the resting or winter stages of its course by which
‘it is again ready to attack the plants the following season. Because
so largely external in development these powdery mildews are
usually comparatively easy of control.

WILT DISEASES—SEEDLING COLLAPSE

The stems or branches of plants may suffer from localized
attack by parasitic fungias wellas from hail, insect attack and
-mechanical agencies. The symptoms which follow will be found
characteristic. In certain ones as in the clover anthracnose and in
the fusarium of clover stems, we have the lesions accompanied by
discolorations in which the fungus occupies a subordinate place
outwardly. ‘On the other hand the spots or sorz of the rusts upon
grains and grasses and the spots caused by the anthracnose of
wheat, oats, rye, etc. show commonly a crowded occupation of the
area by the parasitic fungus.
_ ‘There are many examples of the effects of such lesions.
Fuller discussions will be found under the description of the par-
ticular diseases. ‘The anthracnose of the bean as well as that of
the pea are good illustrations where these attack seedlings. Even
-clearer symptoms come out in potato rosette where the fungus
parasite at early stages of growth may kill off the stem attacked,
while in later attack will cause such impaired development of the
plant that stem or axial lengthening is arrested and a “rosette”
appearance results. A still more striking arrest of stem elongation
takes place in lettuce rosette wherein the roots are destroyed so
largely by the fungus in the soil. (See soil infesting diseases.)

In cankers of branches upon orchard trees the final death of

the immediate branch is preceded by a depressed area invaded by

by the parasite.

PLANT DISEASES NOT BEYOND EXPLANATION

The old mystery attached to disease prevalence can scarcely be
maintained in our day. We have worked out in recent years or
had determined for us the causal relations between the ferment or
parasite and the effects upon the host plant or crop. So far as we
can now discover the reason for the spread of diseases, or of a
DISEASES OF CULTIVATED PLANTS 315

particular disease, is found in the specific disarrangemen\. in the
host plants. This discovery and announcement of these causal
relations are undertaken that proper measures for the control of
diseases may be finally devised and applied. We must always bear
in mind that under favorable conditions plant diseases become epi-
demic and their rapid spread is to be expected.

The host plant, with its climatic adaptations and the parasites
of our crops with their mutual adaptations to their hosts are biolog-
ical factors which are capable of being influenced by prevailing
atmospheric conditions. With cool,'rainy.weather we have brought
about conditions favorable to certain parasitic diseases which will be
inclined to spread while these continue. Other diseases spread under
the conditions which favor them. The more rapid development of
diseases of plants under these favoring circumstances is not beyond
reasonable understanding; there is no mystery about it any more than
in outbreaks of typhoid fever or diphtheria. By apprehending the
differing conditions we may learn to separate the causal from the
merely adventitious factors and thus be the better able to master
the diseases which result.

While we may properly look upon infection by microscopic or
other parasites as the general and usual cause of plant diseases,
there are diseases of wide importance which arise from internal or
physiological disarrangements in the plant. (See Enzymatic. Dis-
eases). In all cases whether of parasitic attack or of physiological
disarrangement due to other causes, the host plant is weakened and
predisposed to death.

GROUPS OF PARASITIC DISEASES

Parasitic diseases may be grouped ina way, according to the
groups of fungi which cause them. ‘This is helpful to the plant
pathologist, though of limited practical guidance, since it requires
microscopic study to determine the causal organisms. A more
useful, limited grouping as is hoped, is proposed below and consists
in making such groups or classes of diseases, as are descriptive of
the general behavior. Such are seedinfesting diseases, soil infest-
ing diseases, root diseases, diseases of foliage, wound troubles,
timber rots, etc. The great mass of diseases are treated under
each host in the descriptive portion arranged alphabetically. The
objects to be attained by this method of arrangement are obvious
and call for no discussion.

NAMING PLANT DISEASES

Plant diseases are named with due regard to the symptoms and
cause of the disease. In the case of enzymatic diseases wherein we
have peculiar variations or yellowing of the leaves, the names given
are mare ar lece deerrintive ‘The same applies to the diseases that
al
316 OHIO EXPERIMENT STATION: BULLETIN 214

Parasitic diseases are named with regard to the organisms
which cause the disease, or to the effects they produce in the host
parts, that is, those diseases which result from attacks of the rust
fungi, (Uredineaae), are properly called rusts; also
the smutty, dirty conditions resulting from the
attacks of the smut fungi, (Usti/agineae), are
known everywhere as smuts; these are well known
and destructive upon grassesand cereals. Thus
we have smuts of oats, corn, wheat, broom corn,
sorghum, millet, blue-grass, etc.

The anthracnoses are produced by a definite
class of fungi, (Melanconiae). The name
anthracnose is applied to a disease of a given
host caused by an organism of this group
and the host name is usually retained, as the
anthracnose of wheat, the anthracnose of rye,
the anthracnose of raspberry, wherein the dis-
eases are caused by species of this group of
parasitic fungi. However, in the case of attack.

Fig.2. Headorpan- Upon the fruit as in the anthracnose of apple, ©
icle of oats destroyed because of the

by loose smut. All the . i"
oat kernels and many bitter taste given

 

  
 
  
  
  
    

  
  
 
 

 

    
 

of their surrounding 1 p

parts have been con- fo the fruit, ae Q oN o

verted into black, sooty have the popular \ y]

(smutty) masses by the name bitter - rot; Q i): KN

loose smut fungus, , ane ee a At\§ dy A ly WINS

Ustilago. in a similar in- 5 i WAX So
stance, viz., that CLI
of the anthrac- Fig. 3. Section through an anthracnose

nose of the grapeberry, the dis- spot (acervulus) of the cucumber anthracnose
1 h 3 fungus (Colletotrichnm lagenarium) showing
colorations of fruit are SO _ thetong, dark hairs (setae) of whose office we
characteristic that it is popularly Ca Sie sesre easing Brseehes ee
“ % yphae) and the spores of this fungus. The
called the birds-eye rot. With members of that division of the commoner
wheat, oats, rye, etc, thename is  @nthracnoses having setae in the acervuliare
lied b ‘i "referred to the genus Codletotrichum, while
applie ecause of the organisms similar ones without setae bear the genus
found. As statedin the preceding  8mes @/ocosportum, Sphaceloma, etc. (See
‘ anthracnoses of apple, grape, lettuce, wheat,
pages, we describe most leaf ats, etc). Serra!
infesting diseases with regard to the
effects the parasites have upon the host; thus we have the leaf-spot dis-
ease resulting from attacks of any one of a number of fungi, chiefly,
however, belonging to the imperfect forms. The shot-hole fungus
of the plum is a good illustration of the naming of a trouble from
the symptoms produced.
A considerable group of diseases are known as downy mildews.
Among these we have the destructive potato late blight and rot,

Phytophthora; also the cucumber disease, Plasmopara, as well as the
DISEASES OF CULTIVATED PLANTS 317

grape downy mildew and the common white molds of the mustard
family. ‘The powdery mildews by reason of the appearance upon
the surface of parts attacked, are descriptively named ‘‘mildews.”
A definite system has been followed in most cases of naming plant
diseases and I trust the results will not be altogether disappointing.

The differences between the species of parasitic or other fungi
are as strongly marked as those of higher plants, even though
microscopic examination is necessary to distinguish these char-
acters; it shows, therefore, that a discriminative system of naming
diseases has a secure foundation.

THE PLANT OR HOST IN RELATION TO DISEASE

As stated elsewhere only closely related plants are usually
subject to attack by a para-
sitic organism, thus it hap-
pens that the tomato as
well as the potato plants
are attacked by the downy
mildew or late blight fungus
of the potato. In general
the true parasites among
our fungi are limited toa
rather narrow range of host
plants; thus we may expect
the potato Phytophthora to
attack several plants of the
potato family (So/anaceae).
The writer proved thissame
was true of the attacks of
downy mildew(Plasmopara)
upon a number of species
belonging to the cucumber
family (Curcurbitaceae).
Since our cereal grains
belong to the same great Fig. 4. Avportion of the epidermis from the upper

1 he grasses (Gram- surface of a cucumber leaf, showing the breathing pores
family ast g ( a (stomates) surrounded by guard cells containing chloro-

-eneue), we expect, and find phyll grains, much magnified. These guard cells, which
that there is a development control the opening and closing of the stomates, are the
Z only epidermal cells that contain this green substance,

of the same diseases Upon _ the others being colorless.
many of them and upon the ‘
grasses growing nearby. In this connection it must be remembered
that clover and alfalfa are not grasses, but legumes.

‘The leaves of the host plant provided as they are with stomates
or breathing pores, minute openings through the epidermal cover-

ing of the leaf, will be attacked through these openings. The spores

 
318 OHIO EXPERIMENT STATION; BULLETIN 214

of parasitic fungi after germinating upon the leaf will likely gain
entrance into the interior leaf tissues through these openings much
more readily than by actual boring through the leaf epidermis.
The illustration, Fig. 4, shows how these openings are distributed

in the epidermis of a cucumber leaf. These stomates are present in

_ the leaf covering upon the outside of all green leaves and in the
epidermis of young growing shoots. In addition to these stomates
certain classes of plants such as the plants of
the mustard family (Cruciferae), as cabbage,
cauliflower, turnip, also the grape, fuchsia, impat-
iens, etc., are provided with water pores—mar-
ginal openings through which the excess water
of the plants isexcreted. ‘These water solutions
of various materials offer a means of growth for
organisms, especially of the minuter forms.
From the culture drops thus formed the para-
site enters the leaf by the water pores. One of
the most destructive known diseases of plants is
the black-rot of cabbage, cauliflower, turnip,
ruta-baga, etc. This is due to a bacterium which
gains entrance very largely through the water
pores just described. So we must bear in mind
that the very avenues of transpiration or excre-
tion, so essential toplant growth,are madeameans
of exposing the plant to the danger of parasitic in-
vasion. ‘This is analogous to the exposure of
human subject to diseases of the respiratory
organs. Atevery turn we find convincing evi-

 

Fig. 5. Margin of cab-
bage leaf showing excreted

water from water pores

after cool night. These
drops contain enough food
for the growth of the black
rot bacteria. The motile
forms may swim through
the water pores into leaf
from such drops. Dead
marginal areas on lower
fragment show results of
this bacterial infection.
(After Smith).

be maintained,

dences of the mutual adaptation of parasitic fungi
to their host plants, in nothing more strongly
marked than in the limitation of the species of
plants attacked by a given parasite as discussed
in the beginning of this paragraph. In view of the
fact that so long as the leaves of a plant continue
to function as leaves, these natural openings will

it will be seen that the risk of exterior infection

from parasitic fungiis continuous for any given plant; it lasts for its
whole growing period.

THE PLANT'S PROTECTION AGAINST PARASITES

In the case of woody growths we have the development of corky
epidermis or bark which seems primarily designed to protect the

interior, living layer from invasions of this sort.

In a similar
DISEASES OF CULTIVATED PLANTS 319

manner the external layer or bark of all growing plants, inciading
herbs, is provided with a protective covering or epidermis. The
skin of the apple or of the grapeand the covering of the potato stem
are allfamiliar and serve this function of protection to the inner
tissues. In young plants there is retained the power of protective
growth in response or resistance to parasitic attack; thus it happens
that the potato scab organism induces the growth of cork cells on
the outside of the potato and makes a roughness. The roughness is
is not the scab fungus but the corky growth of the tubers in
response to the scab attack. Inasimilar manner the attack of the
scab fungus upon the apple results in the roughening of the apple
skin through the development of more protective or wound cork.
The most remarkable example of this multiplication of protecting or
outer cells in response to the attacks of parasitic fungi is found in
“leaf-curl” of the peach and in the pockets or “bladders” of the plum,
where we have such a rapid multiplication of cells in response to the
stimulus of the fungus as to bring about an entire transformation
in the form and structure of the parts. While we may think of this
abnormal development as the result ‘of fungous growth, it is only
indirectly so. It isin fact a response of the host to the stimulus of
the invading fungus. The nature of the stimulus or excitation
exerted by particular parasitic fungi isa highly interesting subject
for investigation.

DISEASE RESISTANCE IN PLANTS

Disease resistance and disease susceptibility are as yet imper-
fectly understood. ‘The cause of the inherent differences in the
tendency of this or that variety to suffer, as with the leaf-curl
in the Elberta variety of peach, the apple scab predisposition
in White Pippin, Winesap and others, may become in
practice, varietal weaknesses. Yetsuch is the commercial super-
iority of some such varieties that they increase in public favor
despite these weaknesses. The great differences among varieties of
fruit in susceptibility tothe diseases which prevail under certain
conditions, is a matter of observation and experience, From the
difficulties involved in breeding a less susceptible or more resistant
type of tree fruit belonging to any commercial variety, increased
resistance is not yet within reach. This applies to established varie-
ties and yet leaves the field open for new sports to be discovered or
for its occupation by less desirable sorts which do not suffer so
severely from disease. This actually happens in the growing of pears
outside of certain favored districts; owing to the ravages of fire
blight, a bacterial disease, the ordinary grower selects less popular
but more resistant varieties for culture.
320 OHIO EXPERIMENT STATION: BULLETIN 214

In the study of disease susceptibility it has been shown that
other features being the same, the percentage of water is an index:
thus, parts having the higher water content are attacked more read-
ily than those with lower water content.

With annual plants or those reproduced each year by tubers or
seed, the opportunities to breed resistant strains are extremely good
and the results obtained are highly promising. Physiological weak-
ness in plants may often be translated in terms of disease suscept-
ibility; this holds with emphasis in vegetables and grains. Apparent
physiological vigor may arise from various causes, and when
expressed in terms of more rapid growth or higher water content
or succulence of the parts may be indeed a source of weakness in the
midst of disease. Selections made for the purpose of securing
resistance to disease are made under conditions of dzsease prevalence
with highest promise. ‘This field of breeding for disease resistance
is one of fruitful promise.

Studies in this line have been made by the Horticultural Depart-
ment of the Station in respect to resistance of potato plants to the
early blight disease. By selection of hills that withstood early
blight attack and planting tubers therefrom and subsequent repeti-
tion of this work (See Bulletin 174) early blight resistant strains
weresecured. The differences between these strains and non-se-
lected tubers in 1908 during the marked prevalence of early blight
was very striking and clearly showed thata tangible resistance
capable of reproduction has been secured. Owing to the wide extent
of this field with vegetables and grains, much may properly be
expected from breeding for disease resistance in the future. Much
progress has been made with cotton resistant to wilt and with musk
melons resistant to leaf blight. For the present other remedial
measures will also need to be pushed.

CONCERNING PARASITIC FUNGI

A fungus (plural, fungi) is a plant, a member of the class called
fungi. ‘The fungi are low in the scale of plant life, being classed
with the alge and other similar plant forms. They are lower still
in the life scale than the mosses and liverworts; above the mosses
come the fern-plants, and above these the seed plants, suchas grasses
grains, clovers, trees, shrubs, herbs and the like, with which we
come in contact every day. The fungi are distinguished from higher
plants as wellas from their nearer relatives, the alge, by the absence:
of green color, and for that reason, we may assume, by the lack of
power to prepare their own food from the mineral substances dis-
solved in water, and from the gases contained in the atmosphere.
DISEASES OF CULTIVATED PLANTS 321

Herein they are marked off from most groups of plants: the fungi
must live upon the substance of living or dead plants or animals. If
they ever possessed the power of utilizing the same foods as most
other plants, this ability has been lost. Parasitism is usually taken
to indicate degeneracy in character. One way of regarding the
fungi is as algz without chlorophyll, to which the latter owe their
green color. As above stated, the fungi are, in the absence of
chlorophyll, forced to live upon the dead remains of plants or
animals, or to prey upon the living organisms.

CLASSES OF FUNGI

Such fungias subsist upon living plants or animals are called
parasitic fungi. A parasite is one who eats at another’s table and
the adjective ‘‘parasitic’” comes from this word, parasite. It is the
parasitic fungi especially of which we must learn, since this class
produce diseases when they attack other plants. The plant attacked
is the “host” plant,
however unwilling the
entertainment of the
sycophant.

Most fungi are very
minute in size and
require the use of a
microscope to study
their parts; certain
ones, however, such as
the mold upon bread
or other foods, may be
seen very easily to
consist of fine, thread- .

a . Fig. 6. Mycelium of the common mold (Mxcor Mucedo).
like g rowths interwov- From the spore lying near the middle of the figure, and strongly
en toge ther, and __ swollen, one sees the thick threads of the mycelium arise; these

A < inturn become richly branched. There are nodivisionsin the
bearing certain round- mycelium. From the level of the mycelium arise three vertical
ed parts upon erect fertile hypae, 2, 4, ¢, of which @ is still very young and that at 4

° is already producing a sporangium containing manyspores. All
branches. Some idea highly magnified. (After Zopf, from Reinke).

of fungus-structure

may be obtained by studying these common molds; that on a dis-
carded melon rind will shows the parts above described, and by the
use of a microscope we may learn that the rounded, ball-like enlarge-
ments just mentioned consist chiefly of small bodies that are
capable of growing into other fungus-threads. (Fig. 6). Such min-
ute parts capable of germinating and again producing the fungus
are called spores. Most sporesare very minute and are not heavier

 
322

OHIO EXPERIMENT STATION: BULLETIN 214

than the other dust particles carried by the wind. The spores of
fungi are the means by which these are most commonly reproduced:

 

 

somewhat after the
manner that the
higher plants about
/ us are reproduced
by their seeds.
While we have
cited the bread mold
Pee as a good illustration
reg to show the struc-
“=a ~—-—i ture of a fungus, it
6 is not. a parasitic
-/ fungus; a mold or
148 like growth which’

PUBR aT?

 

 

Fig. 7. 72. A portion of leaf of pea showing breathing pores and
parasitized by powdery mildew; the horizontal threads (steréle hyphae)
and summer spore bearing parts of the mildew fungus (fertile hyphae)
are distinctly shown. In these latter the septa are evident. 74. A
spore sac (asczs) of the same fungus. 4, 5, 6, show the sucking
organs (azszoria) of the sterile hypae of this fungus; these penetrate
the epidermis of the leaf. 10 shows the spores of the rose mildew
germinating. All highly magnified. (After Tulasne).

+ Note—The stomate in foreground is distorted. See Fig. 2.

lives upon decaying material is called a sapro-
phytic fungus. To this same belong the mush-
rooms or toadstools that may be found in
manure piles, in the woods and in orchards; the

fact that we find them in such places shows that ©

there is decaying organic substance at ihat
point, upon which these plants may subsist. A
like condition is found in the shelf-fungi on old
logs and stumps, onthe under surface of which
we may write our names. Yet if we will usea
hand lens we may often discover this under
surface to be but a network filled with small
openings or pores from which the spores of the
fungus will in time escape. In like measure the
spores of mushrooms are found in similar canals
or upon the sides of the gills beneath the cap of
this sort of fungus. The bacteria, or fission
fungi, are one-celled plants multiplying by divi-

 

Fig. 8. Fertile hyphae
‘conidiophores) of the
downy mildew fungus on
Cardamine, a mustard pro-
truding from astomate; the
one shown in full, bearing
spores at the end of its
branches. Highly magni-
fied. Very similar to this
are the downy mildews of
rape, cucumber, lettuce
and some others, (After
Zopf).

sion and by spore production; with bacteria evident mycelium is
lacking and they are structurally lower in the scale of plant life than
fungi provided witha mycelium. Bacteria are both parasitic and

saprophytic. But to return to parasitic fungi:

.
DISEASES OF CULTIVATED PLANTS 323

PARTICULAR FACTS ABOUT PARASITIC FUNGI

Like the bread mold, or the other fungi just mentioned, parasitic
fungi consist of a growth of threads or hyphae (singular, hypha)
which-do the necessary work of getting food for the parasite; these
also in due time give out certain branches destined to bear spores,
somewhat after the manner that the pear tree has flower clusters,
or the wheat plant forms its dense spike of bloom, both of which are
especially designed to produce seeds from which wheat plant and
pear tree may inturn be grown. The essential parts of a parasitic
fungus are these threads, or hyphae, and the spores produced by
them. ‘The hyphae of the fungus taken collectively are called the
mycelium, which consists of threads that produce no spores (sterile
hyphae) and of those destined for spore production (fertile hyphae.
(Figure 7). Itis to the food getting qualities of the hyphae that the
fungus owes its continual existence, and they in turn arise from a
spore or directly by the growth of some fragment of fungus-thread,
as the Carolina poplar may be grown fromacutting. Yet, while all
parasitic fungi are made up of these few parts, the differences in
form and apparent structure among the several groups are very
marked; differences exist as to the thickness of the hyphae whether
or not the threads are divided into separate cells by divisions like
those at the joints of a bamboo rod, as well as in the manner of spore
formation and in the size, color, form markings and structure of the
spores themselves. It is almost hopeless to undertake to illustrate
types of spore production and spore forms, since these are so varied
and may differ so much at different stages of the development ofa
single given species of fungus, yet we may cite a few examples:

 

Fig.9. Showing the common rust of oats and rye. At Aasmall fragment of rye leaf with
several orange-red, rust sori breaking through the epidermis; these are of the earlier summer
spores (Uredo) or red rust of popular speech. At B asmall fragment of a rye leaf with several
black, rust sori, elongated in form, breaking through the external covering; these are of the later
summer or winter spores (Z¢lewtospores), AandCslightly magnified. At C section through
thg uredosorus of 4; on the slender stalks (basidia) the rough one-celled uredo spores, and
between them a young, two-celled teleutospore, which later alone form the sorus. ¢; ¢; epi-
dermal cells; /, ?, cells of the leaf interior through which runs the mycelium of the fungus. At
D a teleutospore from the black sorus of B; this is divided by a septum into two cells. Similar
uredospores are found in most rusts; similar teleutospores occur in corn rust, wheat rust, etc.,
and in the spores of the cedar apple fungus. C and D considerably magnified. (After Zopf,
324 OHIO EXPERIMENT STATION: BULLETIN 214

Fungus spores may be produced as single spores or in naked
clusters attached to certain branches. We find this sort in the
downy mildew of the cucumber and its relatiye the peronospora of
mustards (Fig. 8); in potato early blight; in fruit rot of plum, cherry,
peach, etc., and later in the spores of apple scab. ‘They may also be
found in dense clusters breaking through the skin of the plant like
the many tubers of a potato breaking through the earth-crust; such
without further conspicuous covering are found in the rust spots,
in the anthracnoses and the like. (Figs. 3and 9). These dense clusters
may arise beneath a special covering resembling nothing so much as
the traditional beehive, but are usually ejected forcibly from a
specially provided opening at the top of the cone or half-ball. (Fig.
10). A yet more interesting class is that in which the spores are
packed so many to a sac
(usually eight) and a large
number of these crowded
into a ball-like, hollow spore-
case, such as we find in
black-Ixnot, strawberry leaf-

spot, the powdery mildews
sat Aan cam Wreitin atetet al-pet and in some other instances.
flexuous mass of spores, ejected from the pycnidium. 4, (Fig. 11). ‘There is yet an-
section of a pycnidium, seated in the leaf tissues and filled other sort in which the

with spores. ¢,agroupofthe spores. All highly mag-
Mified. (After Allescher from Delacroix). spore sacs are abundant

near the surface of the dis-
eased part, as in leaf-curl of the peach, where the maturity of the
fungus is shown by the change in color of the affected leaf surfaces.
Other gradations will be found as one proceeds in this study.

9
008°

  

THE SURVIVAL OF PARASITIC FUNGI

Further, respecting parasitic fungi we must realize that they
are all derived by specific processes of reproduction peculiar to the
fungus in question; in other words spontaneous generation does not
find support among the students of plant diseases.

The presence of any given fungus leads us at once toinfer the
previous existence, somewhere within reach, of a fungus of like
species from which this one was derived by definite methods of
reproduction. Likewise, the destructive prevalence of a parasitic
fungus in any given time and at any given place, assures us of the
necessary supply of spores to start the trouble again under favorable
conditions. In fact, all our study leads us to look through mere
phenomena, mere evidences of disease, to find the specific parasitic
growth which causes them and the favoring conditions under which
DISEASES OF CULTIVATED PLANTS 325

these develop. The spores of fungi serve for them the same purpose
as do the seeds in higher plants; by reason of the extreme smallness
of the spores they are easily transported by the wind and become
deposited like dust particles upon exposed surfaces. Certain resting
spores survive on the fallen leaves or other parts and will be
destroyed if these parts are burned. (See black-knot). The survival
of organisms capable of infecting the new crop is certainly to be
expected in plant diseases as in epidemic disorders among people.

Some fungi which produce disease survive by their thread-like
parts (mycedium) ina manner similar to the survival of Canada thistle
quack-grass and the mints among troublesome weeds by their visible
underground stems. A good illustration of this form of survival is
found in the case of potato rosette; in this disease the masses of
mycelium (sc/erotia) remain upon the surface of the potato tubers
and unless destroyed by treatment of the seed will be ready for
immediate attack upon the growing plants (sprouts), even before
these have reached the outer air and taken on a green color.

Similar survival may occur in cultivated soils, especially where
the same or closely allied crops are grown in succession. ‘Thus the
same fungus as that.of the potato disease first named, survives in
greenhouse soils or in celery soils outdoors.

RESTING FORMS AMONG FUNGI

The active parasitic phases of fungi necessarily coincide with
the activity of the host plants; it, therefore, follows in our temp-
erate climates with alternating periods of activity and rest of
growth and practical somnolence, that the parasites require to be
mutually adapted to intermittent activity. Some spores will survive
the brief rest period between harvest and seed time, as in a number
of the various grain smuts and in grain anthracnoses. Here they are
found simply adherent to the seed grain.

Seed infesting parasites like the loose smut of wheat, the
anthracnose of pea and bean, and a variety of other vigoraus species
survive as resting mycelium, which remains virtually inactive so
long as the parasitized seed is not exposed to conditions of moisture
and temperature such as bring about germination.

’ ‘There are endless gradations between these instances of “rest-
ing’? mycelium and the protected fruit cases of the higher type of
fungi. Thus the perithecia or closed fruit bodies of the wheat scab
fungus, develop shortly after harvest upon the infected glumes or
culms of wheat, and may be observed by the unaided eye, as black
bodies seated upon the pink mass of ene: summer form. ‘These fruit
bodies in this case are the kind called ‘ ‘perithecia,’ which contain
326 OHIO EXPERIMENT STATION: BULLETIN 214

within them spore-sacs of a nearly fixed number and each sac con-
tains a fixed number of spores of definite form for each species. A
great many fungi develop these ‘housed’? or protected forms
during the dormant period, and indeed, spore development may
proceed in the periods of lower temperature.

With the perithecial or sporehouse form of wheat scab, (Gzbber-
ella), the spore sacs are formed during the later summer, in our
latitude, and these spore sacs disappear before midwinter. For each
genus or species under study, peculiar time relations of development
may be discovered. The perithecial or spore sac (acsigerous) form
just described, or some comparable development of the spores under
a definite cover-form,
is viewed asa more or
less ultimate stage in
the development of the
higher fungi— the
summit in the cycle of
their development.

The rot of stone
fruits, such as peach,
plum, cherry and the
like, is commonly
known only in its
conidial development

 

Fig. 11. Section through a spore case (ferithecium), late
winter stage of black-knot fungus, showing spore sacs (asc?) called Botrytis. Recent-

within. Beside it, three asci containing winter spores or asco- :
spores, eight in each sac, arranged in adefinite manner. Along ly Norton has discov-

with these are thread-like hyphae known as paraphyses ered the Sclerotinia or

ascigerous stage devel-
oped from the mummy fruits in which the fungus lay dormant fora
time awaiting spring or summer conditions.

The bitter-rot of apple and its cycle of development not long
since brought to light in Illinois, also shows the relation of the apple
mummies, decayed by attacks of this anthracnose, to its survival.
The fungus lives over in the old rotted fruits, acted upon by bitter-
rot alone, which hang upon the trees. The fungus may also survive
in branch cankers upon the tree adjacent to mummies of the bitter-
rot. Inthese branch cankers the spore sac or perithecial stage of
the fungus is developed. Upon the coming of warm showery
weather about early June, new spores are produced from either
mummies or cankers and new infection may occur upon the new
fruits. The problem of the control of this disease, therefore involves
a knowiedge of its manner of survival.
DISEASES OF CULTIVATED PLANTS 327

ALTERNATION OF HOSTS IN FUNGUS SURVIVAL

This relation of alternating forms in the life cycle of a given
parasitic species, to its survival, has been mentioned in wheat scab
wherein we have the Fusarzum or pink mold and the Gibberella
forms; in rot of stone fruit where we find Bo@rytis and Sclerotinia
forms, and inapple anthracnose or bitter-rot where we discover the
Gloeosporium followed by the Glomorella ascospores. In these
instances there seems no real need for the advent of another host
plant. In other groups of fungi, notably among the Uvredinee or
rusts, we discover in certain species, that survival is accompanied
by a necessary change of host plant. The apple rust is known in
summer to attack the leaves and fruit of apple, thorn apple
(Crataegus), june-berry and mountain ash. This is the aecidial or
cluster-cup stage of the apple rust and has its counterpart in the
aecidiospores or cluster-cups of the wheat rust upon barberry as
well. With apple rust we climb far on the plant ladder and find the
teleutospores of rust survive upon the cedar treesas branch enlarge-
ments called cedar apples (Gymnosporangium). 'The dry looking
apples upon the cedar trees take onanew form during spring
showers when they become great, jelly-like masses which emit the
teleutospores of the rust, to be carried to apple, juneberry and
crataegus leaves by whatever agency is available.

The relation of cedar trees to the prevalence of apple rust isa
practical matter for each orchardist. It may be better to make
firewood of the cedar trees than to combat the apple rust in his
orchards. A similar problem as between the barberry hedges
which adorn rural England, and the virulence of wheat rust in their
grain fields, may also be raised. With us we have plenty of grain
rust in the absence of barberry hedges. An adaptive form of
survival apparently takes the place of the alternating hosts, and we
still have the wheat rust.

The instances given are simply illustrative and the student of
plant pathology will discover many more in the course of his study.
Likewise a careful perusal of the special part of this bulletin will
show other instances of survival under many various and instructive
conditions.

HOW THESE PARASITES ROB THE HOSTS

There is an old saying about the stable door and the stolen
horse; similar application may be made for plants-and parasitic fungi
in a manner which we shall presently perceive. To obtain food we
must reach the source of supply; the manner of reaching it is less
important than the result. Now it occurs that cultivated and wild
328 OHIO EXPERIMENT STATION: BULLETIN 214

plants of the higher classes are wrapped about by a covering of skin
or bark, and the food-filled juices are within; to feed upon any living
host the parasite must gain access to the internal tissues of that
host. Itso happens that there are minute openings or stomates
(breathing pores) through the skin of leaves and of young green
stems; these openings are as necessary as the stable door, and
through them the thief may enter. (See Fig 4). Were these open-

ings to become entirely closed the plant would languish, and remain-
ing open, they constantly offer a way for the tender tip of the
growing germ thread of a fungus to pushits way through the plant
covering and to luxuriate within the host upon the substance of the
plant.

Once within, the fungus thrives, rapidly multiplies its
branches, and if in summer, commonly
thrusts its fertile threads through
some of these breathing pores to bear
its spores outside where they may
become more widely distributed than
if remaining within the tissues of the
host plant. Should, however, the

 

Fig. 12. Haustoria of the fungus of the

grape downy mildew penetrating cells of
grape stem. The shaded portion shows
the mycelium of the fungus growing be-
tween the cells, sending haustoria, ¢ a,
into the interior ofthe cells. (After Scrib-
ner from Farlow).

Note: In this figure the lower row of
cells have the form of empty epidermal
cells in which the fungus. would find little

winter season be near, ‘resting spores
may be formed, or their formation be
provided for within the leaves, or dis-
eased parts, as in grape downy mil-
dew, elm-leaf disease and in black-knot
of plumandcherry. ‘Thus the cycle.
of development continues indefinitely

to subsist upon. Farlow’s original figure

does not give these cells such form. unless some agency intervene to

destroy the spores, to prevent their
germination, or the parasite itself so exhaust the host plantas to
destroy it entirely and the fungus perish for lack of suitable nidus.
However, this rarely occurs, not perhaps, so often as men are guilty
of killing the goose which lays the golden egg. Herein, we meet
another fact, namely, that parasitic fungi of a given kind are limited
toa particular host plant of a certain species, or toa small number
of related plants, so that if a congenial host is lacking the fungus
will not thrive.

The fungus threads growing within any plant will not flourish
if simply passing between the cells of the host; penetrating organs
pierce the cell-walls and are able to absorb nutriment from the cell
interior. (Fig. 12). The diverse forms of sucking organs, and the
peculiar structures of fungus threads in these situations would in
themselves require much study and investigation to present them
properly. We must further conceive that a fungus may often
DISEASES OF CULTIVATED PLANTS 329

penetrate the bark of a tree for example, if aided by rifts caused by
freezing or similar disturbances, to say nothing of the openings
offered by wounds, the breaking of branches, etc. A recent illustra-
tion of the danger of rifts in the bark of trees is offered by the
chestnut disease which is proving so destructive near New York
City. Few parasitic fungi have that penetrating power of thrusting
the haustoria through the plant covering such as we find in the case
of the dodder that twines about and robs the wild herbs and shrubs
of the woods and fields as well as the cultivated flax and clovers.
HOW PARASITIC FUNGI AFFECT THE HOST

We know the cumulative effects of insufficient food supply; these
effects must hold for plants attacked by parasitic fungi. Aside from
the nutriment diverted to the parasite, there is reduced functional
vigor of leaf, stem or root, and the loss becomes increased in this
way. Letallthe leaves be parasitized, or let even three-fourths of
them be entirely soattacked, and we may look for great loss of foliage,
possibly entire loss of fruit and the detailed effects of diminished
vigor, unripened wood, or by repetition, entire destruction of the
host. Usually the effects are of many gradations, but in all cases of
leaf-parasites the entire plant must suffer. We have learned that
bacteria may, in a suitable medium, destroy themselves by the
formation or emission of poisonous products. which are fatal alike to
the bacteria and to animals, or even man; that such takes place within
plants parasitized by fungi remains in doubt, and may be disre-
garded for the present. The results of impaired function in the
parts are serious enough to demand our attention. It is altogether
‘probable that future investigations will modify our views upon
some points.

There are many curious transformations and malformations
resulting from the attacks of parasitic fungi, simply by the multi-
plication of cells of wound cork or other tissues in the effort of the
host to shut off the fungus, not because the fungus consists of such
amass of tissues. (See leaf-curl of peach).

While exceedingly interesting to trace the effects of the white
mold on shepherd’s purse and on the garden purslane, as well as the
effects of bramble rust, cabbage club-root and a number of others,
the principle above pointed out will be found generally applicable,
and it is to the reactions of the host plant that the excrescences or
malformations are chiefly attributable.

It may further be stated that artificial cultures of parasitic fungi,
either upon culture media or living plants are constantly adding to
our knowledge in these lines.

BENEFICIAL ORGANISMS: ROOT NODULES, ETC.

While realizing the losses caused by parasitic fungi and bacteria
we may not hastily condemn all fungi and bacteria. One of the most
profound influences of aging culture of the soil is the beneficial
330 OHIO EXPERIMENT STATION: BULLETIN 214

effects in nitrogen fixing, exerted by the root nodule bacteria of
leguminous plants. The well known beneficial effects of the root
nodule bacterium upon clover has made rotation in clover an agricul-
tural necessity. The species or forms of root nodule bacteria
required on alfalfa, cowpeas, vetches, etc., have become recognized
as factors of consequence in our efforts at seeding and new species
of legumes on the farm.

A less understood relation between certain fungi which develop
as mycorrhiza upon the roots of some deciduous trees and notably
on conifers may not be passed. Herein we may find an explanation
of rotation in forest species when reforestation crops are to be
grown.

THE PROOF OF PARASITIC CAUSE IN PLANT DISEASE

The mere presence of a fungus, determined by the microscope
in diseased tissues of the plant, does not prove the case against the
organism found. Itis not easy at all times to be certain whether
discovered spores belong to this or that organism, or group of organ-
isms, although with certain groups as the anthracnoses, species of
Fusarium, etc, the spore forms give somewhat clear evidence. The
differences between parasitic and saprophytic fungi are not always
simple matters admitting of ready determination; further, we must
bear in mind that after a parasite has caused death or even minor
lesions in a plant, the organisms of decay may be expected to appear
to do their great work as the scavengers of the world. The fungi or
bacteria found in a dying plant may be both saprophytic and para-
sitic, or these may be only saprophytic.

The methods of proof of parasitic cause in the bacterial diseases
of animals including man have been extended to the study of bacterial
diseases of plants and finally to the diseases caused by parasitic
fungi. These methods consist of a group of rigorous exact rules
which are stated by Dr. E. F. Smith in the following terms:

(a) Constant association of the organism with the disease.

(b) Isolation of the organism from the diseased tissues and careful study of
the same in pure cultures on various media.

(c) Production of the characteristic signs and lesions of the disease by inoc-
ulations from pure cultures into healthy plants.

(d) Discovery of the organism in the inoculated, diseased plants, re-isola-
tion of the same, and growth on various media until it is determined beyond
doubt that the bacteria in question are identical with the organism which was
inoculated.

Smith—Bacteria in Relation to Plant Diseases. Vol. 1, p. 9.
DISEASES OF CULTIVATED PLANTS 331

While these methods and rules are stated with special reference
to bacteria as the cause of disease, they apply with equal force to
the proof of cause in the case of any given parasitic fungus. These
methods require rigorous and exact work in the isolation and subse-
quent culture of the parasite upon sterile media, followed by equally
careful inoculation work using these pure cultures as a source of the
organism.

METHOD OF INOCULATION FROM CULTURES

The methods of inoculation tried by the investigator are of great
importance. ‘These determine, in fact, the success or non-success
of his efforts. There must be adaptation of the method to the life
history of the parasite and the developmental stages of the host
plant, including the appearance of the parts more commonly attacked
by it.

 

 

 

 

 

 

Fig. 13. This shows method of infecting field plots by means of the hand spray pump, using the
washings of samples of wheat and other grains. The washing of grain containing spores of disease
such as anthracnose or scab may be used, Cultures may also be sprayed upon plants in this way or
by means of blow-bottle in smallertests. (From Bul. 203, Ohio Experiment Station).

Following the methods of earlier bacteriologists, needle pricks
are often employed both in the inoculation of fungiand bacteria into
plants. One seeking to pursue a special line of inoculations will need
in all cases to study his conditions as wellas the methods of other
investigators. ‘Thus, doubtless, inoculations like those of Phytoph-
thora and Plasmopara may be best attained by using drops of sterile
water to carry the spores. The same principle applies in field
332 OHIO EXPERIMENT STATION: BULLETIN 214

methods upon many crops. In the case of grain diseases, notably
anthracnose and scab upon wheat, rye, oats and grasses, inocula-
tions may be made by spraying the cultures upon the grain ata
proper stage of its development.

While some groups of fungi do not lend themselves readily to
culture upon the usual media, it is the aim of plant pathology to
make this possible witha constantly increasing number of these
parasites.

CULTURE PROOF NOT ALWAYS POSSIBLE

While in all cases of bacterial diseases where the body of the
organism is so little different from that ofthe bacteria of decay,
fermentation, etc., these rigorous proofs are required before the
disease is listed as of proven bacterial origin, we do not find it nec-
essary in practice to reprove again the case as against frequently
occurring species of fungi associated with particular plant diseases.
This does not make it less necessary to prove all cases as to para-
sitic cause, although the practicability in any single laboratory of
pathology is admittedly one of narrow limits.

ENZYMATIC DISEASES OF PLANTS: CHLOROSIS OR PANACHURE

To this form of physiological breakdown, induced however, by
specific causes recently determined, we attribute some very wide-
spread and injurious diseases which belong under the head of
chlorosis. Peach yellows, possibly peach rosette, frenching or mosaic
disease in tobacco, and in general variegated or special yellow foliage
types of plants as in Arundo, Acer and other genera of plants belong
here. The yellows in peach has long been studied, as also the
tobacco mosaic disease. In yellows the contagious character of the
disease and its transmission in pruning by contact of parts of the
harness of team and by or through the atmosphere has been
recorded.

A few years ago it was determined by Beierjink and by Hunger
that this infection exists as a chemical compound or compounds of
complex nature belonging to the oxidizing ferments ofa group called
the oxidases. Oxidase, peroxidase and others of these ferments are
known. They act by breaking down or oxidizing the plant leaf
tissues and especially the chlorophyll or leaf-green of foliage and
young tissues, converting it into xanthophyll. The tests for these ©
ferments are of some importance. Woods and others have shown
their action with peroxid of hydrogen.

From a practical point of view the transmission of the ferments, |
and, therefore, of the disease, by touching first diseased and then
healthy foliage is: rather surprising. The work of Hunger in Java |
DISEASES OF CULTIVATED PLANTS 333

upon the transmission of the tobacco mosaic disease. makes the risk
of transmission from diseased to healthy plants by such handling,
stand out clearly. ‘This line of transmission was verified on tobacco
by the writer’s assistant in 1903 (See Bulletin 156, of this Station).

While the same class of proof for peach yellows is very difficult,
owing to the latent nature of the disease for some months after first
infection, the actual results of infection from nearby diseased trees
make clear the danger of such exposure and the necessity for the
destruction of diseased trees. Chemical examination of variegated
or chlorose tissues shows the same compounds, the oxidases, etc., to
be present and to account for the transformation of the leaf-green
or chlorophyll, into xanthophyll, or leaf yellow. ‘Thus by degrees
apparent plant disease mysteries are solved. ‘The weakness of
variegated plants and their ready susceptibiity to attacks of para-
sitic fungi are now explained by thisimpaired condition of the leaf
parts.

PLANT DISEASES TRANSMITTED IN THE SEED

The public in general little realizes how many diseases of plants
are transmitted in the seed, although as the years pass the general
dissemination of knowledge concerning infection by spores and by
germs has partly prepared the way. The public mind does not
longer expect something to grow from nothing. The treatment of
seed grain, as wheat, oats, barley, etc., todestroy adhering spores
of the smut fungi, and thus prevent these smuts in the crop, has
been known for many years. In the early days of the Agricultural
Experiment Stations, these doctrines and practices in this regard
were widely disseminated, new impetus being given by the success-
ful use of hot water following’ the methods of Jensen in Denmark;
but despite the conquest of the practical control over the order
Ustiligineae, the smuts, we have only really begun to study the
matter of seed infecting diseases produced by seed infesting fungi.
These seed infesting fungi are of two types, viz, first, those whose
spores adhere to the seed grain as in the case of the smuts of grains
generally, and second, and more exactly, those fungi which
develop upon or within the seed largely by their threads or mycel-
ium, and may, or may not, prevent the germination of the infested
seed grain. Our knowledge of these strictly seed infesting fungi is
quite recent; we may point to the work of Prof. Bolley and his
assistants at the North Dakota Experiment Station, especially upon
the matter of flax diseases; to the work of Dr. Halsted in New Jersey
and to Bulletin 173 of this Station by Van Hook. With the tendency
to continuous growing of flax, in the west there was developed m
334 OHIO EXPERIMENT STATION: BULLETIN 214

that new area specific seed and soil troubles which have been proved
to be perpetuated in the infected seed. An anthracnose of flax and
a Fusarium attacking flax seed are examples.

No less conspicuous is the case of the blight fungus of peas,
Ascochyti pist, which is also an anthracnose, and the allied anthrac-
nose of beans, Colletotrichum lagenarium. Investigations made at
this Station by Van Hook show the source of the trouble with peas
to be the infected seed employed and show also that seed treatment
will not destroy these internal fungi without destroying the vitality
of the seed. It was further shown that the source of relief zs in
growing healthy seed through the use of fungicides upon thé pea
vines from which seed is gathered; likewise that infection way
remain in the soil, (See Bulletin 173).

 

Fig. 14. Showing physician’s centrifuge and other apparatus used in making
examinations of grain washings for smut spores and spores of other diseases adher-
ing to the exterior of seed. The flasks at the right show samples of washed grain.
Those at the left show amounts of grain and water used. The glass tubes in con-
tainer are used in the metal holders of the centrifuge. The precipitates in bottoms
of tubes were obtained from washing of oats and wheat samples in flasks. (From
Bul. 203),

More recent work at this Station has shown the presence of seed
infesting and seed infecting diseases in wheat. (See Bulletin 203).
The illustration, Fig. 15, exhibits the germinating seeds of wheat
with the outgrowth of the parasitic ‘fungus (Fusarium) which we
find associated with wheat scab. Thisis upon seed grains (kernels)
that are not destroyed by the fungus; many of the kernels of scabby.
DISEASES OF CULTIVATED PLANTS 335

heads will not germinate. It was also found in continuous wheat
land as much as 6 percent of the young wheat plants were destroyed
in the fall by this same parasite which appears to survive in the soil
under continuous ‘wheat growing as well as to be propagated in the
seed grain.

 

Fig. 15. This shows results from germinating ten wheat kernels in
Petri dish containing agar. Both the agar and the kernels were sterilized.
After five days it was found that five kernels had produced healthy plantlets,
and four kernels had germinated but were attacked by the scab fungus,
Fusarium, and two by anotherfungus. One kernel in the center did not
grow and gave only growth of the scab fungus, Pusarzum, (From Bul. 203).

HOW TO EXAMINE SEEDS FOR INFECTION

Recently good success has been obtained in the laboratory of this
Department in determining the presence of certain seed infesting
fungi in seed wheat, oats, rye, etc. In regard tothe matter of
adhering spores this is accomplished by making washings of the
seed in distilled water and separating the spores from the washings
by means ofa physician’s centrifuge. (Fig. 14). The spores and
similar particles washed from the seeds are thus collected in the
bottom of the tubes of the centrifuge and may be identified by
microscopic examination. (Fig. 16).
336 OHIO EXPERIMENT STATION: BULLETIN 214

Examples may be multiplied to illustrate the range of seed
infection both by adhering spores and by internal development of the
mycelium of the invading fungus. Many of these are treated under
the particular diseases of the crops. ‘The bean, pea, barley, broom-
corn, flax, millet, potato,
sorghum, rye, sweet-po-
tato, and wheat will all
furnish examples. Not
only have we to test the
actual survivalof the par-
asites thus found but we
must discover the behav-_
ior of the disease with
respect to the germina-
tion and seedling plants
which grow from such
infected seeds or tubers.
Examination for infection
of seed bulbs and tubers
may be made either with
or without the growth of

 

 

 

 

 

Fig. 16. Microscopic photographs
from centrifuge precipitates of wheat
washings. 2, from wheat washings,
narrow, slightly curved anthracnose
spores, small spherical, loose smut
spores, large spore of stinking smut
and portions of the setae of anthrac-
nose. 4, from wheat washings, small,
loose smut spores, large stinking
smut spores and curved scab spores,
All magnified about 180 times.

plants from them. With
potato scab and rosette,
the external scab effects
or the sclerotia of Ahz-
zoctonia are not difficult
tosee. With the latter the
moistened tubers show _ >
marked color contrasts and make the work easier. These diseases
are reached by seed treatment.

Where the infection is internal by the threads or mycelium of
the fungus, the seeds may be germinated in Petri dishes where the
kernels are surrounded bya moisture retaining, sterile medium

 

 

 
DISEASES OF CULTIVATED PLANTS 337

such as agar or gelatin. This method has been worked out in
Bulletin 203 and may often be applicable. The illustrations above
will show the results in these cases as before referred to. With
internal tuber infesting diseases as
in the bacterial wilt disease of the
potato, the Fusarium wilt or dry-
rot fungus of the potato and the
soil-rot of the sweet potato, we must
go further than mere external
examination. For the two named
wilt diseases of potato, infection
usually shows earliest at the stem
end. Thin slices across this stem
end of the tubers will show wheth-
er or not there is discoloration in
the vessels. In the absence of infec-
tion there will be no discoloration
with bacterial infection by Bacillus
solanacearum, black areas or rings
will be seen in these tissues while
tubers infected with /usarium
oxysporum will show local areas of
browned or blackened tissues.
This infection applies usually to
“harvest time. As the infect.on
advances, one-half the length of the
tuber or even more may become
infected. In all cases sections from
sterilized tubers may be used asa
source of cultures in Petri dishes.
The same applies to soil rot of
sweet potato. These diseases are
not reached by seed treatment.

 

 

 

 

 

 

THE LIMITS IN SEED TREATMENT —-
Fig. 17. Pea stem showing lesion from

It will be apparent that serious _ blight fungus, Ascochyta pisi, near surface

ate oe iN of ground. Thisfungus came from the seed
limits hold in regard to seed treat- pea. (Natural size). From Bul. 173.
ments. Where the spores are

external and simply adhering to the seed grain, treatment will
destroy these spores if rightly adapted to the seed in question and
the germination need not be much, ifany impaired. On the other
hand where the seed infection is internal rather than external, grave

doubts arise as to the possibility of successful seed treatment.
338 OHIO EXPERIMENT STATION: BULLETIN 214

It has not been found possible in thé cases of seed peas when infected
with the blight fungus, or of seed wheat, rye, etc.,infected with the
scab and other fungi to apply any seed treatment which would
destroy the infecting fungus without destroying the vitality of the
seed grain. In general we may say that where the seed infection or
fungus spores, etc., are external to the visible or germinable grain,
seed disinfection through treatment is possible, but for the internal
fungiitis rarely possible. The loose smut of wheat may be amen-
able to special seed treatment with only partial loss of vitality in
the seed wheat.

 

 

 

 

 

Fig. 18. Potato tubers attacked by Dry Rot Fusarium, showing sections near the stem-end of
infected potatotubers. This infection may be easily discovered by cross sections made with a sharp
knife, and sections from sterilized tubers gives culturesin Petri disnes. At times the discolorations
extend to the middle of the tuber. (From a photograph by T. F, Manns). .

METHODS OF SEED TREATMENT

The methods of seed treatment heretofore employed are set
forth in the spray calendar and consist in an immersion of the seed
in hot water of definite temperatures or in solutions of formaldehyde
of different strengths. The formaldehyde solutions may also be
employed to sprinkle piles of seed grain and in this manner less
handling of the grain is required. More recently it has been pro-
posed to disinfect seed potatoes, onions, forage, etc., through fumi-
gation with formaldehyde gas liberated by boiling the solution, or
better by mixing formaldehyde or formalin solutions with pulver-'
ized potassium permanganate by which the gas is liberated.

With seeds, tubers, roots, bulbs, etc., the limitations of the
treatment are not so narrow and these may be immersed for longer
or shorter periods in solutions of corrosive sublimate, formalde-
hyde, etc., or they may be exposed to fumigation with gaseous
formaldehyde as has just been stated. (See Seed and Soil Treat-
ment, pages 344 and 345 following.
DISEASES OF CULTIVATED PLANTS 339

SOIL INFESTING PARASITES IN FIELD AND FORCING HOUSE

The cultivated soil is a medium in which many species of
bacteria and fungi survive from year to year. The public is famil-
iar with the doctrine of bacterial infection or inoculation of the soil
in its relation tothe nodules or tubercles of clover, alfalfa, soy beans,
cowpeas and other cultivated plants of the Family of Leguminosae.
One form of bacterium is not sufficient for both clover and alfalfa.
This flora of the soil both in relation to bacteria and fungi of consid-
erable range of species, is enriched by the applications of manure
and by the practices of culture; by this is meant that the growing ofa
given crop a second time ora third time consecutively in the soil
increases the probability that the plant roots remaining in the soil
are carried over from one crop to the next together with root
parasites which cause dis-
ease in the plants of this
crop. Manifestly, like-
wise, ifin preparation for
a given crop to be grown
for the first time upon the
land, rather liberal appli-
cations are made of fresh
stable manure containing
spores or mycelium, more
especially the resting
forms of mycelium called
sclerotia, the soil will be-
come infected by this
manurial application.
While this source of. in-
fection is rather rare in
field culture we bave spe-

tific examples as in the ;
isease of potatoe Fig. 19. Bases of potato stems (Carman No. 38) collected
scab dise s is om oes June 7, 1902, Cheshire Ohio, showing injuries by Rhizoctonia,
transmitted in this Way; The shaded areas are darker lesions occupied by an abund-
ugar beets ence of Rhizoctonia hyphae; the tops showed conspicuous
the scab of es & > ns Rosette effects. Reduced from Bulletin No, 139.
may be carried in like

manner. Butin forcinghouse culture where heavy applications of
manure are made, the chances are greatly increased that soil infec-
ion will be produced from the manure.

It is of value to remember that seed infesting or seed infecting
organisms are also very largely capable of survival in the soil nidus
of cultivated soils, thus our troubles multiply adequately if our
care be inadequate to avoid them.

 
340 OHIO EXPERIMENT STATION: BULLETIN 214

 

 

 

 

 

Fig. 20. This shows root portions of seedling lettuce plants with dark spots, lesions caused by
attacks of the rosette fungus, /th/zoctonia, With the younger plants these attacks cause large mortality
and in very small seedlings the stem of plantlet may early collapse after the manner shown in
rotting specimens, (From Circular No. 57).

THE AVOIDANCE AND PREVENTION OF SOIL INFESTING DISEASES

We, perhaps, may assert that the law of nature is that of a diver-
sified plant covering; at any rate the law of successful culture will
permit of statement in termsofcrop rotation. And it is true that as
culture ages the number and seriousness of plant diseases increase
almost in geometric ratio. Itis further conspicuously true with
respect to those areas devoted largely to continuous culture ina
single crop or ina group of closely related crops such as the growing
of wheat in Western United States and Canada, also in the growing
of flax and other crops. Potato growing in San Joaquin county,
California, illustrates this danger. Muck lands devoted to vegetable
culture, tempt the grower to continue his crops of celery, onions,
etc. Here we haveasatrue result the accumulation of diseases
which attack these plants; thus for field culture we are seep caae

 
DISEASES OF CULTIVATED PLANTS 341

a serious decrease in the return from the crop on the special type of
soil. While for general field culture avoidance of conditions may be
successful, this is by no meansa simple matter. Rotation is often
absolutely necessary, but this same rotation will not rid the soil of
the onion smut fungus, nor of some other parasites such as in the
case of the club-root fungus of cabbage and related plants. In these
cases some soil treatment must be applied to field areas. In the case
of the onion smut it is sufficient to apply a formalin. drip which will
fall with the seed and disinfect the soil layer in proximity to the seed.
This is effective because the smut fungus can penetrate the germ-
inating onion plant only in the earlier stages of growth. On the
other hand with cabbage club-root, where plants are transplanted
from the beds in which they are grown, some general method of soil
treatment which involves the soil mass is more effective. In this
case it is the application of stone lime or caustic lime in liberal quant-
ities. These examples are only illustrative of general conditions to be
met with. In the case of potato scab, itis found necessary both to
disinfect the seed where scab is present, even toa limited extent,
and to plant upon new soil not infested with the scab organism.
Potato rosette is certainly an acid loving parasite.

 

 

 

 

Ne tts

Fig. 21. Lower portion of two celery plants Showing effects of root rot, RAzzoctonia, It will be
observed that nearly all the roots of the plants have rotted off in consequence of the attack. (From Cir-
cular No. 72).
342 OHIO EXPERIMENT STATION: BULLETIN 214

Under the diseases described for each plant, methods of avoid-
ance and treatment are indicated and the diligent student will find
other instances of similar character mentioned therein.

SOIL TREATMENT IN THE FORCING HOUSE

About our great centers of population have grown up conspicu-
ous developments of the forcing house industry; large areas are
covered with glass and these hothouses are maintained at the
necessary temperatures for the production of the special green
crops found profitable, At the same time the soil of the hothouse
beds is very liberally manured and enriched further by applications
of commercial fertilizers. Not only do these applications of manure
tend to enrich the flora of the soil and to introduce particular root
parasites, but the decay of the organic matter of the manure also
tends to produce humus acids in considerable quantities. Along with
these are brought parasitic eelworms which are peculiarly fatal to
curcurbitaceous plants, to violets and to some other hothouse crops.

_ Next to the eelworms the most conspicuous organism in our area is
the sterile fungus Rhizoctonia, whose resting formsor sclerotia may
be readily introduced in manure. To meet this indoor soil infection,
special methods of soil sterilization had to be developed, since soil
rotation is practically impossible in the forcing house.

These methods of treatment are in brief, steaming oi the soil to
render it practically sterile, so far as these parasites are concerned,
and a method of formalin drenching. This method of steaming is
ideal, or almost so, in its results upon sandy or loamy soils, but often
entails unfavorable changes in heavy silty or clay soils. Essentially,
it consists in burying a series of perforated pipes in the soil at inter-
vals, covering the surface of the beds and passing live steam in suffic-
ient volume into the pipes. These pipes are prepared insets with cross
heads and boiler connections and are perforated at desired distances.
The surface of the bed is covered with canvas and the steam passed
into the system for such period as is required to heat the soil toa
temperature from 180° to 212° Fahz., to be maintained for one hour
or more. ‘This applies to high pressure boilers; for low pressure or
hot water heating systems where the steam is applied in subdrains,
four to five hours steaming will be required with a pressure of six
to seven pounds. ‘This treatment is effective for destruction of the
eelworms or nematodes of cucumbers, violets and - -lettuce, the rot or
drop fungus of lettuce, the rosette fungus, and in general of all soil
infesting parasites.
DISEASES OF CULTIVATED PLANTS 343

Another method, the formaldehyde or formalin drench, has
proved successful for the control of AAzzoctonza in greenhouse soils.
This consists in a solution of 40 percent formaldehyde in water, say
at the rate of two to four pounds in 50gallons of water. ‘This is
applied at the rate of one gallon per square foot of area and will
involve a very severe wetting down of the bed and prevent immediate
resetting of the soil owing to the persistence of the formaldehyde.
One secondary effect of formaldehyde drench and lime in sandy
soils in the forcing house was an increased yield of lettuce amounting
from 60 to 90 percent over the ordinary crop. This was explained
on the assumption that the parasitic fungus was destroyed and
certain other inhibiting organisms at the same time.

THE BEST FORCING HOUSE PRACTICE

The best forcing house practice will contemplate a recurrent
disinfection or sterilization of the soil during the idle period; it
should be preceded by whatever applications of limestone and manure
that are to be made to the soil, then after thorough working and appli-
cation of water to correct unevenness of moisture the soil may be
sterilized by steam, or the formaldehyde drench be applied with
assurance of results: obviously also this treatment must extend most
vigorously to the plant beds and bring healthy seedlings to soil in
which the soil parasites have been destroyed.

‘The following tables of seed and soil treatments taken from the
spray calendar will be of more use than extended description or
discussion:
OHIO EXPERIMENT STATION: BULLETIN 214

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346 OHIO EXPERIMENT STATION: BULLETIN 214

ROOT DISEASES AND ROOT-ROT FUNGI OF ORCHARDS

Diseases upon the roots of herbaceous plants are very commonly
due to soil infesting parasites. As explained under that topic, the
soil conditions may be favorable to certain parasitic organisms or
without being especially suited to them soils become infested with
fungi which tend to remain indefinitely and become a source of loss
in crops and effort. See lettuce rosette, tobacco root-rot, potato
dry-rot and root-rot of violet.

The root-rots of woody growths are commonly more or less
truly wood invading fungi of the semi-parasitic type and become of
interest to foresters as wellas orchardists. A partial exception to this
wood-invading character of these root-rot fungi is found in a recently
discovered development of the tobacco and violet root-rot fungus,
Thielavia basicola Zopf., upon catalpa seedlings in nursery. However,
since even tree seedlings in their early stages have not developed their
woody tissues to any great extent, they are susceptible to the same
root parasites as are found on herbs. ‘This will likely explain cases
like that cited on catalpa and the trouble may pass as the seedlings
become older. Yet it must be confessed that this still raises a ques-
tion as to the effect of the general parasitism of even Thielavia upon
the rootlets of trees like catalpa.

In forest woodlots, root-rots are likely to become of increasing
effect. Wherever these tend to limit the reproduction of certain
species in the woodlot, they will be injurious. In this respect they
may prove an added reason for the rotation of conifers with decid-
uous growths. In coppice or cut-over lands such as prevail in the
charcoal furnace districts of Ohio, the roots and stumps of the
parent stem must be an eventual menace to the'new growths which
spring up about them. The exposure to the wood fungi which
become timber or heart-rot sorts will be very great in all such cases.
The gradual invasion of the new growths must often occur when
these approach a size that gives a considerable heartwood cylinder.
These are the great sources of trouble in coppice reproduction of
timber trees.

Root-rots in orchard plantings are known more especially when
these are made following oak and other species somewhat after the
manner of coppice conditions. The rhizomorphic development of
these root-rots is difficult to determine but is usually referred to
Agaricus melleus (Armillaria mellea). See root-rots of apple,
peach, etc.

An especial feature to be noted in root-rots of all sorts are the
soil conditions as to excess moisture and aeration of the soil. In
silty or clay soils of close texture and coagulable nature, with excess
moisture, serious conditions arise. Any traces of root-rot fungus
DISEASES OF CULTIVATED PLANTS 347

under such conditions will involve increased risks. The necessity
for drainage will usually be apparent and due consideration of the
limits of certain orchard trees needs also to be given. Cherry trees
and even peach and apple trees will not survive under moisture con-
ditions wherein plum and pear trees may grow with profit.

Orchard replants in ‘‘clinker’”’ locations wherein failures have
been numerous, will raise these questions of root-rots and relative
adaptability of different orchard trees. Rotation planting, as pear or
plum after apple, plum after cherry, etc., may at times succeed and
replace unsightly gaps in the orchard by flourishing trees of another
sort. At present, drainage and aeration are our known methods of
restricting root-rots under out-door conditions.

PARASITIC FOLIAGE DISEASES

Foliage diseases of every sort are caused by oxygen loving or
aerobic species of parasites, and very often this development on the
leaves consists of the imperfect forms of the fungus life history.
‘These forms are none the less aggressive and injurious for this
reason, but the exact manner of survival from year to year becomes
important wherever not known.. ‘The application of this to prevent-
ive measures in the control of these diseases upon foliage and fruit
is seen in the case of apple scab, the monilia rot of plums, peaches,
cherries, etc., and in apple bitter-rot. These last two rot troubles
survive in the “mummy”? or dry rotted fruits and this explains the
reason for the oft repeated injunction to destroy all “‘mummies” in
addition to spraying operations. ‘The bitter-rot of apples is propa-
gated by means of summer branch cankers on the tree, as brought
out-in recent years. Other leaf forms survive on the fallen leaves
or possibly in bud scales as with the leaf curl and “‘bladders”’ of the
Exoascae. A large number must live over on the branches.

Parasites upon foliage soon become apparent from the
spots on the leaves and dropping of fruit resulting. This dropping
may come asaresult of impaired vigor by reason of disease—‘then
it is later, but is more often the direct result of parasitic attack by
the disease upon the young fruits. Herein as elsewhere the philoso-
phy. of fungicides comes to our relief. A good foliage fungicide is a
relatively insoluble compound which will not greatly injure the
leaves with which it is in contact. The remedies for foliage troubles
are applied in anticipation of attack and for the purpose of checking
the fungus when it may appear. ‘The relative efficiencies of various
fungicides in early summer will possibly depend upon the sticking
qualities of the sprays.
348 OHIO EXPERIMENT STATION: BULLETIN 214

Foliage diseases, moreover, are liable to recur each year and

- tnis is an added reason for anticipatory treatments to ward them off.
- Foliage diseases may not be neglected with impunity since the leaf ts the
plant's vital working organ and the plant must suffer from its im-

pairment.

BITING AND SUCKING INSECTS AND LEAF DISEASES

The part played by insects which wound the leaf epidermis, in
the spread of leaf diseases, is often very important. Such wounding

 

 

 

 

 

Fig. 22. Showing sections of blades of oats attacked by green
lice (aphides), The right hand specimen shows type of injury re-
sulting from the sucking of the aphis. In case these lice are carry-
ing the organisms of oat blade blight, this sucking will lead to
infection by the disease. (From a photograph by T. F. Manns),

of the leaf or green
stem whether by
insects such as flea
beetles, foliage eat-
ing worms, or by
sucking insects such
as mites, leaf hopp-
ers and plant lice,
opens the way for
the spores of para-
sitic fungi or of bac-
teria or mere molds,
any one of which
may be injurious to
the leaf. The eariy
blight disease of

’ potatoes is a good

example. In seasons
when there aremany
of these little black
flea-beetles to punc-
ture the leaves, the
thorough control of
both these insects
and the early blight,
Alternaria fungus,
is called for. ' Many
fungi of doubtful
penetrating powers
are truly injurious
when they follow in-
sect puncturesof the
leaves. Fortunately
both these are se-

cured by Bordeaux sprays. The reasons for such applications are
of double character since they are to combat both the insect and the

fungus to follow it.
DISEASES OF CULTIVATED PLANTS 349

With shade trees the leaf hoppers and mites may be so numer-
ous that tip-burn and various leaf dying results from the injuries or
punctures they inflict.

A more startling relation is that of the blade blight of oats, a
recently investigated bacterial trouble.
This bacterium is distributed and
inoculated very obviously by the
aphids or green flies (plant lice), and
other sucking insects which prevailed
during the seasons of 1907 and 1908
upon oats almost throughout Ohio.
For fuller details see Blade Blight
under Oats, and Bulletin 210.

 

WOUNDS AND WOUND INFECTION

With woody growths, especially
in trees which attain considerable size,
we have the various phenomena of
disease infection through wounds; this
infection later becoming evident by
reason of decays set upin the woody
tissues. Of course, in instances such
as the bark disease of the chestnut,
Diaporthe parasitica Murr., the dis-
ease may penetrate the living tissues.
Not so, generally, in wounds of woody
plants. Any large woody growth, as
in forest or shade trees and in larger
fruit trees, shows the combination of
an external or living sapwood layer Winget Reel atacoen wae
and an internal dead or _ heart- — with large branch cut off. Below this
wood cylinder. The commoner forms  jytinay nas iia yen Ani ae
of wound infections are attributable cap is nine inches across, This shade
to those species of fungi which cause ane oe ome ee
decay of this dead heartwood. Among pole. (From a photograph by J. M.
these are the long list of saprophytic, Smee"
agarics, polypores and stereums. Because of the fact that this
heartwood cylinder is dead, these saprophytic species of fungi, once
they gain entrance into it, flourish there and invade the wood toa
very great extent, even by adaptation to parasitic habit extending
their work into the living parts causing death. The removal ofa
large branch of a shade tree or a fruit tree, unless the wound thus

 

 

 

 
350 OHIO EXPERIMENT STATION: BULLETIN 214

formed is properly protected by dressing, opens the way for spores
of these fungi which cause timber decay to obtain a start and thus

eventually to invade the heartwood of the interior. For dressing cut.

off branches, asphaltum is admirable; in its lack gas tar is good, and
either is better than ordinary paints.

 

 

 

 

Fig. 24. A wound parasite (Pleurotus ulmarius) on the trunk of a
maple tree. (After Freeman, Minnesota Plant Diseases).

There is always to be borne in mind that the protection of the
woody cylinder of trees depends on its being covered by the living
layer of sap wood. Every branch of considerable size connects
directly with the extensive heart cylinder; we thus see that the
wound fungi which attack the heart wood are the timber decays and
their presence emphasizes the need for care in providing protection
for all wounds, especially those caused by pruning. i

Any decay becoming established inthe dead heartwood may
extend for long distances through this dead wood and in the end so

destroy it as to be ina position to invade the external or sapwood _

layer.
DISEASES OF CULTIVATED PLANTS 351

In addition to the exposure of the internal woody cylinder to
these decays, we have sap-rots due to various species of fungi which
belong on the border line between the parasitic and saprophytic sorts:
Among them are species of Fomes, Polyporus, Lenzites, etc. Any
wound of the sapwood even though
it does not reach to the dark heart-
wood, exposes to the danger of this
infection, and with infection, to all
the consequences of sapwood decay
and premature death of the tree.-
These decays and those of heart-
wood are inline with those of the
rots of structural timbers, but we
are at this time interested only in
their effects on the parts of the
living plants.

 

TIMBER ROTS AND TIMBER
PRESERVATION

The decay of dead logs, wood-
en frameworks, or other structural
timbers is caused by the attacks of
.saprophytic fungi belonging to the
gill and pore fungi mentioned under
wounds; these are of the great class
of basidium bearing fungi, to which
the fleshy forms, everywhere more
or less abundant, belong. ‘The
most of them are included in the
“‘mushrooms,’ which there is a Fig. 25. Another wound parasite (a
strong impulse now to study and sett ol Sir The fungus ain’
illustrate by photogra phs. ‘These tree (an oak), and as shown by the fungus
timbers are dead and are subjected [ting tates, is etadully, rorresing

to invasion by timber infecting the photograph was taken, (After Free-
species wherever the conditionsas  _™""
toair and moisture are suchas to favor their development. Dry
timbers are not subject to such attack because lacking the requisite
moisture for the organism. Floors and other timbers of houses
adjacent to the earth or to unheated cellars are often attacked by
rot-causing species. The timbers of trestles, railway ties and the
bases of fence, telephone and telegraph posts, where inserted into
the earth or in contact withit, are kept sufficiently moist to invite

attacks of this sort.

 

 

 

 
352 OHIO EXPERIMENT STATION: BULLETIN 214

Wood that has been invaded by such fungi is reduced to the
state called punk: that is, the wood fibers and arrangement in vessels
to which the timber owes its strength, are broken down by the
invasion of the fungus which flourishes at the expense of this woody
tissue. There is no help for timber after it has once been attacked
by rot fungi. Whatever preventive measures are taken must precede
the attack. The most
effective means of
timber preservation
is to cause it to be
injected or permeat-
ed with creosote or
other antiseptics.
This is done by plac-
ing the timbers in
vats containing the
solution and extract-
ing the air from the
timbers so far as
possible. The per-
manence of the
effects of such tim-
ber treatment de-
pends upon the
resistance offered by
the material used to
f] gradual solution by
water. In the case
of creosote the re-
sults are quite satis-
factory; with chlorid

° of zinc, subsequent
Fig. 26. Fruiting bodies of the fatty Pholiota (Phol/ota adipose, solution takes place

in a wound of an oak tree trunk. (After Freeman). ; : :

\ too readily, while
with crude petroleum there isa tendency toward the evaporation of
this substance when injected. The increasing cost of timber will
stimulate timber treatments by making treatment profitable. One
drawback at present is the necessity toimport creosote for use in
such work; possibly refiinery by-products from petroleum of a

character analogous to asphaltum may find application in timber
treatment.

 

 

 

 
DISEASES OF CULTIVATED PLANTS 353

ATMOSPHERIC CONDITIONS AS AFFECTING PLANT DISEASES

The relation between weather and the prevalence of certain ;
plant diseases has been often recorded. The diseases which prevail
are none the less parasitic, the difference exists solely in the
temperature and moisture conditions of the atmosphere. Here we
must distinguish clearly between the cause of the diseases and
the conditions which favor the given diseases.

Certain parasitic fungi develop more rapidly under cooler con-
ditions than the normal or average while others are favored by higher
temperatures; all fungi are favored by large amounts of moisture
when these stop short of water immersion and shutting out the
needed air. In temperature we have an optimum which usually lies
within certain maximum and minimum limits for any given species,
but this temperature optimum varies with the organism; it is a
matter which admits of exact determination for any organism. As
to moisture, an abundant supply of water is the optimum for most
fungi with which we deal in plant disease investigations.

In these atmospheric conditions of temperature and moisture
the seasons of the year, in our climate, vary one with another. The
seasons of heavy rainfall are commonly those of low temperatures by
reason of the check on temperatures exerted by evaporation.
Further, our weather service records show a tendency for our
seasons to come in groups of cooler alternating with groups of
warmer seasons; that is, we may have several years as with 1904 to
1907 (excepting parts of 1906) in which the mean monthly tempera-
tures of those months which affect crops were decidedly below the
normal or average. Evidently this normal lying as it does between
the extremes, is surpassed by the warmer seasons which are said to
be above normal. We have likewise, other alternating groups of
years in which the season’s temperatures are decidedly above the
normal,

The effects of these cool seasons upon diseases are most clearly
shown in outbreaks of leaf-curl of the peach and plum bladders in
early season, and of potato late blight and rot, Phytophthora infes-
tans, upon the potatocrop. It is understood that plenty of moisture
is the usual accompaniment ofa cool season; from the combined
effect of this supply of moisture and cool weather we have outbreaks
of the potato disease even in northern Ohio where it does not appear
certainly to survive from year to year. Such groups of cool seasons
culminate as arule in particularly injurious outbreaks of the potato
Phytophthora with us;in more northerly situations, the disease is
present nearly every season, but the outbreaks culminate with
favorable weather conditions of excessive rains and lowered

temperatures.
354 OHIO EXPERIMENT STATION: BULLETIN 214

Stress has been laid upon the downy mildew of potato and
cucumber respectively. It must not be inferred that other diseases
do not offer like contrasts between dry, hot seasons and those of
heavy precipitation and low temperatures accompanied by relatively
high atmospheric humidity. Mention has already been made of the
greater prevalence of the shot-hole disease of the plum and leaf-spot
of cherry, Cylindrosporium padi, in rainy seasons over drier ones.
The same facts will apply with respect to practically all external
parasites of plants as in the scab fungus on the apple, the rot of
plum, cherry and peach, and to the countless number of foliage
diseases with which we deal from year to year.

Contrasting with the potato Phytophthora is the allied disease
of curcurbits, the downy mildew, lasmopara cubensis, which
appears to flourish during our hot seasons and to disappear during
the cool ones where grouped as above described. The writer has
suggested that this Plasmopara does not survive in our climate but
is carried northward each year by its conidia alone; the extent of
spread will thus be limited by the length of period favorable to it.
This period must be one of relatively high temperatures since this
parasite is more widely distributed near the tropics. All these
instances only make more clear the intricacies of the mutual
adaptations of parasite and host which have resulted from the long
periods in which these dwell together.

MEAN SUMMER TEMPERATURES AND RAINFALL IN OHIO, 1883-1909

 

 

 

 

 

 

 

 

 

 

 

Mean temperatures degrees Fahr. Mean Rainfall, inches

Year Three 3 Mos.
May June_| July -|August|/months}| May June | July |August] Total
Mean inches

58.0 69.0 72.1 68.2 69.8 5.72 4.25 4.16 .88 | 10.29
60.4 71.1 71. 70.8 71.1 3.87 2.96 3.83 45 8.24
59.5 67.1 7. 68.9 70.4 3.97 4.34 3.20 .33 | 13.87
62.2 67.5 72. 70.9 70.1 23 3.53 2.88 .62 | 10.03
66.0 71.0 71. 77.9 75.6 87 3.85 2.16 .39 8.40
58.8 70.4 72, 70.4 71.0 77 3.41 4.4 16 | 12.97
60.2 7 72. 69.1 69.4 aa 4.13 4.25 -50 9.88
59.2 73.3 3B. 68.8 71.7 5.52 4.50 Led -70 | 11.19
68.0 71.0 69. 70.0 70.0 -20 4.82 3.82 .O7 | 11.71
59.0 73.0 2B. 71.0 72.3 6.32 5.61 3.80 -99 | 12.40
58.3 70.6 14. 70.7 71.9 4.97 3.34 2.49 17 8.00
60.0 71.3 “ 71.2 72.3 4.00 2.65 1.56 67 5.88
61.1 72.0 Vis 73.5 72.4 1.80 2.47 2.00 96 7.43
67.9 69.5 73.2 71.8 71.5 2.67 4.81 8.11 38 6.30
66.3 68.1 75.5 69.4 71.0 3.93 2.85 4.65 -72 | 10.22
61.0 71.9 76. 73.5 73.5 4.10 2.96 3.98 4.50 | 11.34
63.3 71.5 74.1 73.7 73.1 4.32 2.96 4.18 82 96
62.9 69.8 74.1 76.3 73.4 2.40 2.99 4.62 .68 | 11.29
59.0 70.9 fim! 73.1 74.0 69 4.38 2.73 .82 | 10.43
62.6 66.9 74, 67.4 69.0 09 7.48 4.69 .67 | 13.84
63.9 64.4 72. 70.7 69.3 82 3.97 3.67 -20 | 10.84

60.7 68.4 71.4 68.8 69.5 ia 2.88 4.13 2.74 9.7
60.7 69.2 73. 71.7 71.3 63 4.72 3.93 4.46 | 13.11
61.3 69.8 72, 74.6 72.2 17 3.41 5.14 77 | 13.32
54.5 65.6 723 69.5 69.2 AT 4.57 5.36 48 | 12.41

62.8 69.2 23. 71.2 71.4 4.72 2.52 4.08 .59 9

68.7 70.1 | *69.6 | *70.3 70.0 4.72 5.86 | *4.05 | *5.21 6.04
Ohio, ’83-’09 ...... 60.6 69.6 73.44 | 71.3 71.4 3.88 3.93 4.08 3.12 | 10.82

 

 

 

 

 

 

 

 

 

 

 

 

 

* Records Wooster only, not included in other than 1909 averages.
DISEASES OF CULTIVATED PLANTS 355

The blade blight of oats, a bacterial disease, has been found to
be much influenced if not largely controlled by atmospheric con-
ditions and perhaps more especially those of the earlier summer.
These factors have been recently presented bya bulletin of this
Department (See Bulletin 210). This publication contains a fuller
table with respect to early summer atmospheric conditions. The

_development of the Fusarium blight and dry-rot fungus as a wide-
spread and serious disease of potato plants causing premature dying
and reduced yields is of interest here. The outbreaks in Europe
seem to be associated with atmospheric conditions in spring and
early summer. We need fuller studies on these inter-relations.

Insistence is here again made upon the observed relations
between atmospheric conditions and parasitic diseases of plants that
the grower may be stimulated to greater effort at close observation
when the need exists and the student may be aided in his interpre-
tation of the vast array of apparently inconsistent and complex facts
by which he is to be instructed.

REMEDIES FOR PLANT DISEASES--FUNGICIDES

In no other line of applied science has America made more rapid
progress than in the matter of plant disease remedies. While the
genera! doctrine of parasitism and the transmission of parasitic
diseases are thoroughly investigated and widely published in Europe,
the application of remedies and the interest in disease prevention
fall much behind the practices in America. Indeed, the writer’s
attention was in 1908-9 forcibly called to this matter by the statement
of a prominent American Pathologist as to the relatively great
advancement in America ove: the old world in this regard. Prob-
ably this greater progress is due to the greater readiness with
which Americans engaged in crop production, accept the teachings
of scientists and make practical applications of the results obtained.

Among remedies for plant diseases we must include all treat-
ments which tend to restrict or prevent the recurrence of diseases,
that is, alltreatments which remedy infections or limit the spread
of parasitic attack.

SEED AND SOIL TREATMENT

Seed and soil treatments naturally belong here; while somewhat
full discussion has been given on pages 342-345, it is necessary to
recall the measures employed in seed treatments as well as in
soil disinfections. In the seed treatments high temperatures, as in
the hot water, or the application of a germicide as in solutions of
formaldehyde are applied to the seed grain todestroy adhering
356 OHIO EXPERIMENT STATION: BULLETIN 214

spores. In the treatment of tubers and rootsas the potato, etc.,
longer soakings with solution of formaldehyde or corrosive sublimate
are required to kill not only external spores but resting forms of
fungi such as sclerotia, etc.

With soil treatments we have the problem of killing out soil
infesting organisthns such as nematodes or eelworms and Rhizoctonia,
Botrytis, lettuce drop, etc., among the fungi. All these results are
obtained by thoroughly steaming the soil. In a measure the same
results are also obtained from a formaldehyde drench as elsewhere
described.

Fumigation for the destruction of seed infesting fungi or cutting
infesting insects is of the same character and must be named here.
The fumigation of nursery cuttings with hydro-cyanic gas is
effective as is also the fumigation of stored grain with carbon
bisulfid. We must also consider that wound coverings are methods
of prevention in plant disease, since these coverings of asphaltum
creosote, gas tar, paraffine and even of paint serve the purpose of
excluding wound fungi which might otherwise cause serious decays.
All these treatments that have just been enumerated apply to the
treatment of the soil or of seeds and plants in resting condition.
The great problem of keeping down infection during the growing
period yet remains for the application of spray mixtures.

SPRAYING WITH FUNGICIDES--INSOLUBLE COPPER COMPOUNDS

The progress made in the control of plant diseases through
sprays since Millardet’s discovery of Bordeaux mixture (bouillon
bordelaise) near Bordeaux, France, in 1883 shows how great was
then and is still, the need for effective fungicides. The materials
from which Bordeaux mixture is made consist of copper sulfate
(blue vitriol) calcium oxid and hydroxid (caustic lime) and water.
In the making of the mixture the copper sulfate is dissolved in water
and should be diluted with a considerable amount of water; the lime
is slaked or converted into lime putty from which a milk of lime is
prepared. These two mixtures with the copper sulfate in aqueous
solution and calcium hydroxid in suspension, mixed together makea
chemical reaction by which the calcium in the lime displaces in part
the copper in the copper sulfate, forming on one hand calcium sul-
fate or gypsum, and on the other the various combinations of lime
with the metallic copper thus liberated. The actual reactions have
been variously interpreted. More recent investigations show that
several basic sulfates of copper and lime are produced. Whether
any hydroxid of copper is produced has been questioned by Picker-
ing, an English investigator. The light blue coloris due to suspended
DISEASES OF CULTIVATED PLANTS 357

particles of these com pounds which are evidently the effective avents
in fungicidal action. ‘These insoluble light blue copper compounds
which, in this divided condition, are held in suspension in the liquid
give it the characteristic color. The essential needs in making
Bordeaux mixture are the presence of enough or even an excess of
the base, calcium (lime), so that none of the copper will remain in
soluble form as sulfate. This on the other hand involves the more
or less complete change of the soluble copper into relatively insol-
uble, blue-colored copper compounds of another sort.

The philosophy of spray action is based first of all upon the
absence of injurious effects from the lime products and from the
copper compounds produced, when sprayed upon green foliage. In
the second place, upon the effectiveness of these insoluble copper
compounds through solution in the presence of moisture and carbon
dioxid in the atmosphere, to destroy or prevent the growth and
development of parasitic fungi. The time during which these insol-
uble copper compounds will be effective must depend upon the rate
of growth in the plant parts and the adhesiveness of the application.
The essential feature to be remembered is this; the insoluble or
slowly soluble copper compounds become available by
solution as needed. Where excess of fungicide is employed this has
a certain danger upon apple or other foliage during showery
weather and in all cases the strength is adapted to the host crop.
Coincident with the spraying period there is frequent complaint
of injury to apple foliage. Here we have solution effected more
rapidly than is safe for the host; normally this risk is slight, but
may be overcome by necessary modifications. Another matter is
the amount, the number of gallons of the given fungicide to use;
with more complete spraying appliances and high pressure of appli-
cation, larger amounts and more complete covering of the parts are
the rule. Recent results show that when the amount of copper
in the mixture is near to the danger line these heavier applications
increase the risk.

In the early translations from the French the strength of Bor-
deaux mixture was placed higher than is now the practice. For
Ohio the following formula has been the rule for many years:

STANDARD BORDEAUX MIXTURE

Copper sulfate (blue vitriol).........ccc660 ceeeeeeees 4 pounds.
Caustic lime (unslaked).........:ccsssesseseeee coeeeees 4 pounds.
Water to make... ieee ceeeee ceeeeceeeeneeeeeneees 50 gallons.

This is a 4-4-50 formula—a 2-2-50 formula is also
used at times.
In making Bordeaux mixture, the copper sulfate may be dis-
solved in hot water (about 2 gallons) or better by suspending the
sulfate contained in cheese-cloth sack, in a large vessel of cold water.
358 OHIO EXPERIMENT STATION: BULLETIN 214

By using large quantities of both blue vitriol and water, say 50
pounds of copper sulfate and 50 gallons of water, a stock solution
may be prepared, so that each gallon will contain one pound of the
blue vitriol. In each case the solution of copper sulfate should be
diluted say to one-half of tank capacity before admixture with the
milk of lime.

The quicklime is slaked and then stirred to make milk of lime,
adding water as needed to dothis. The necessary amount of this
milk of lime should be diluted to about 40 or 50 percent of the tank
capacity and then run intoa mixing tank with equal flow of corre-

~sponding volume of copper sulfate solution before same is run into
spray tank or barrel,

All Bordeaux mixture formulae are useful as a vehicle in which
arsenical sprays are added to serve as insecticides.

THE USE OF STICKERS IN SPRAY MIXTURES

Some experiments made in different parts of the country have
shown beneficial results from the use of other materials added, such
as sugar solution, soap, resin soap, etc., to increase the adhesiveness
of the spray. In some spraying experiments by the Entomological
Department of this Station, laundry soap was used effectively as a
sticker to hold arsenical compounds in checking the berry worm or
grape worm (See Circular No. 63).

The writer has proposed a modification of Bordeaux mixture
which has been called ‘“‘Bordeaux Mixture and Iron Sticker.”

The following formula has been recommended:

BORDEAUX MIXTURE AND IRON STICKER

Copper sulfate (blue vitriol).........cceccsceeseecesees 2 pounds.
Iron sulfate (copperas)..........ccssssssssesseeceeees 2-4 pounds.
Caustic: Mimesssecs giedises sevacestsavvadepeen sere: aveceicen 4-6 pounds.
Water fomake wi. siguasesnaneiaseccnarceustaiaesieecarten 50 gallons,

In this spray the iron sulfate is added in order that it may be
precipitated by the lime and serve asa more complete sticker than
is provided by the standard Bordeaux mixture. It would appear
possible by the weak solution as given for the copper compound and by
this possible efficient sticker to make the reduced amount of the
copper sulfate do the work as fungicide just as effectively and with
less risk of foliage injury than with the standard Bordeaux mixture.
The trials made up to this time upon apples in full foliage, upon
grapes and upon potatoes indicate that the spray is efficient. The
iron sulfate ts not considered a fungicide.
DISEASES OF CULTIVATED PLANTS 359

SOLUBLE COPPER COMPOUNDS AS SPRAYS

Whenever it becomes necessary to continue spraying upon
fruit as ripening approachesa more soluble copper compound than
Bordeaux mixture must be employed or the spray will remain upon
the fruit at marketing. The remaining spray, if excessive, injures
the marketable character of the crop. Various sprays have been
proposed for use at these critical times. The call for them has
come in keeping down the black-rot on the grape and in the control
of the several late season diseases of fruit, like the bitter-rot and
black-rot of apple. The most satisfactory soluble copper sprays
appear to be ammoniacal solution of copper carbonate or Soda Bor-
deaux mixture. ;

For the former the following formula is given:

AMMONIACAL SOLUTION OF COPPER CARBONATE

Copper’ Carbon aterwrcassiesinessuneesecsisasisawcmsersnnannye 6 ounces.
ATMODI A) cin ceanweaniiyiten nexeeveoniannandhemeiwedstwess about 3 pints.
(Enough to dissolve the copper carbonate and no more).
Water €0: Makes tcc ccise cadiecntesecnaamsidand sadacea cons 50 gallons.

This isan effective spray made according to formula for the
late applications upon grape and upon appleas maturity approaches.
Itis to be understood that this formula is not intended to make
“eauceleste’’ which is a different preparation. No more than enough
ammonia is added to convert the copper carbonate from insoluble to
soluble form in the presence of water. A soluble salt of ammonia
and copper is really produced. The proper times at which to make
applications of fungicide as sprays has been carefully worked out in
practice and directions are included in the spray calendars. There
isa good reason in nearly every case for making the applications at
the time recommended, since these sprays are timed to check the
development of the parasite; if put on too long in advance the spray
may be displaced, if put on too late the damage will occur without a
possible means of prevention. All sprays as stated before are made
in anticipation or in advance of actual danger from parasitic diseases.

SULFUR COMPOUNDS AS FUNGICIDES

Various preparations of the sulfids of alkalis and alkaline earths
have been proposed as fungicides. A larger use has been made of
the lime-sulfut formulae which have come into use largely for check-
ing scale insects. These mixtures are made by boiling together caustic
lime and flowers of sulfur in the presence of water. By this heating
process a combination is effected between the calcium and the sulfur,
and sulfids of various compositions are formed. For practical
purposes the color reactions are used as a guide. This spray applied
,

360 OHIO EXPERIMENT STATION: BULLETIN 214

in the dormant period or just as the buds are swelling is effective
against the scale insects and is also efficientasafungicide. The
lime-sulfur has very largely displaced other fungicides against leaf-
curl of the peach. More recently the self-boiled lime-sulfur formula
has been proposed. It promises to be effective upon peach trees in
foliage. This isa much more dilute formula than the one used upon
dormant trees; both are described in the spray calendar. Latterly,
various dilutions of the lime-sulfur residues formed when lime and
sulfur are boiled together, have come into use as sprays for
orchard use.

SOLUTIONS FOR SEED TREATMENTS AND DISINFECTION:
FORMALDEHYDE SOLUTIONS

Formaldehyde in 40 percent solution is obtained upon the market.
Solutions of this 40 percent compound in water are effective in seed
and soil treatments and for disinfection. The following are standard
strengths:

For oats and wheat, 1 1b, or pint 40% formaldehyde to 40 or 50 gals. water,
For potato scab and rosette, % pint of formaldehyde to 15 gals. water.
For onion smut, 1 1b. of formaldehyde to 25 or 33% gals. of water.

For soil drench, 2 to 4 1bs, of formaldehyde to 50 gals. of water.

CORROSIVE SUBLIMATE SOLUTION

For treatment of potato tubers and for laboratory disinfection,
mercuric chlorid, corrosive sublimate, is used as follows:

Corrosive sublimate 00... .....cccceccsecsscsnesseeuee one 2 ounces.
Water nis isise ceases ceasreanena nen le @atiaieeey 15% gallons,

 

GASEOUS DISINFECTION WITH FUNGICIDES

Latterly the methods used for the disinfection of houses wherein
patients have suffered from contagious diseases such as diphtheria,
scarlet fever, etc., have been extended to the treatment of plant
diseases. The following formula of the Maine Board of Health is
applicable to the details below given:

FORMALDEHYDE GAS

Commercial 40% formaldehyde ...........cccscecceee 3 pounds,
Potassium permanganate crystals .........0...... 23 ounces.
Sufficient for 1000 cu. ft. of space occupied by crates or
trays. .

The following suggestions from the spray calendar of 1908 will
be helpful tostudents or experimenters who have not access to other
literature:

“Enclose open tiers or piles of slat crates filled with dry onions,
potatoes, etc., in tight room or oiled tent of canvas buried in earth
about the base. Generate the formaldehyde gas in a flat bottomed
DISEASES OF CULTIVATED PLANTS 361

dish or pan of adequate capacity by placing one of the materials, as
the, liquid formaldehyde, in the pan, and adding the other the last
thing before retiring. Then close tight and allow to remain closed
24 to 48 hours.

-Proportionate or multiple unit amounts may be taken for
smaller or larger enclosed spaces. Applicable to fumigation of seed
potatoes for scab, sweet potatoes for rot troubles and to newly
gathered, dry onions before storing for winter.

For grain elevators to disinfect against conditions there or for
mass treatment of seed oats and wheatasimilar use is made of
formaldehyde gas.

ROT DISEASE LOSSES IN STORAGE

No sharp Jine can be drawn between diseases of edible plant
products which usually infect these crops previous to harvest, and
the rots, molds or decays in such fruits and vegetables during
storage. It has seemed best, for this reason, to insert here a brief
discussion of these storage troubles which apply to products grown
in our region. We can scarcely be called on to present the facts
concerning the diseases of citrus fruits in storage or in transit.

All growers of fruits and vegetables in our state are liable,

_ however, to have had losses from rots of fruits and vegetables during
storage upon the farm. Inthe more recent custom of concentrating
such storage products in cold storage plants, especially constructed
for that purpose, the prohlem has only been transferred or trans-
planted: the difficulties have not been entizely overcome..

For the fruits known as perishable, namely, for peaches, plums,
cherries and grapes, the custom of brief storage has become well
established; the rots or other injuries, such as those that come from
crushing, are well known. ‘The storage rots are not different from
those commonly found in the orchards—indeed, they are usually
the common soft-rot of stone fruits, Monzlia fructigena. Storage
or transit losses from it are but an accentuation of orchard con-
ditions. Also with the stone fruits, as a result of bruising and
shipment, we have various of the common molds which develop on
the bruised surfaces. ‘The more usual ones are the common bread
mold, Mucor, the blue mold, Penzcillium, or the almost equally
frequent form of green mold, Aspergillus. None of these, how-
ever, is likely to penetrate very deeply and bea serious enemy of
these fruits. This arises, however, not so much out of the lack of
ability toinjure by these mold attacks, as from the very brief period
of time which these tender skinned stone fruits are held before
consumption. As has been pointed out by Powell and Smith, the
* 362 OHIO EXPERIMENT STATION: BULLETIN 214

same common molds, including especially Penicillium, possibly with
the aid of others, are sources of serious loss in the handling of citrus
fruits—oranges, lemons, etc., during their prolonged periods of
transit and storage.

In the case of grapes the losses are almost altogether due to
breaking of the skin following which molds and bacteria are liable to
appear under favorable conditions.

STORAGE ROTS OF APPLES AND PEARS

With apples the commonest storage rot for our district is doubt-
less also the commonest orchard rot, namely, black-rot, due to the-
black-rot fungus, Sphaeropsis malorum Berk. All are familiar with
orchard conditions liable to prevail at ripening time. ‘This fungus
is generally found, especially in orchards of mixed varieties, because
some sorts are commonly attacked by it. The same fungus causes
cankers upon branches of the susceptible varieties and is usually
well distributed over orchards. The punctures of worms or of bees,
or wounds caused by mechanical injuries such as occur in wind-falls,
and the various drops at picking time, afford easy entrance for the
fungus. In consequence we must expect that the fruits which have
been in any way punctured or injured, have also been exposed to
infection by the black-rot fungus. Such infected fruits are very
liable to rot because of the progress of the fungus, if conditions are
favorable. The high temperatures of storage sheds and ordinary
freight cars during October and early November in our climate, are
such as favor its development.

In the light of our present knowledge the best we can dois to
transfer fruit as soon as possible to storage where the temperatures
are low enough to restrict the fungus. It follows without saying,
that good results are obtained only from absolutely sound fruit, and
the low temperatures of cold storage houses, 42 degrees or below,
may be relied upon to check this rot to a very large extent, provided
only sound fruits are placed in storage.

Naturally the discussion which follows under the storage of
onions will raise the question here as to the practicability of gaseous
disinfection of apples by the use of formaldehyde gas. It would
seem possible under favorable weather conditions when fruit can be
gathered dry and brought into storage houses in that condition, to
disinfect the fruits by the formaldehyde gas method. Of course it
follows that the period of disinfection will be brief in order that
little or no gas will be absorbed by moist or exposed fruit surfaces,
since formaldehyde is objectionable in foodstuffs. The time of
fumigation may not need to be more than about half that used for
potatoes or onions, and the strength of the formula may even be
modified. The aim would be the destruction of external spores, etc.,
which certainly are a menace at all times.
DISEASES OF CULTIVATED PLANTS 363

The bitter-rot fungus, (Glomerelia rufomaculans (Berk.) Von
Schrenk) may also develop in storage apples where these have become
attacked by it before harvest. The bitter-rot may be more common
upon late summer and fall varieties in transit, than in ordinary
winter storage. Certain sweet apples, such as Bentley Sweet, are
very susceptible to bitter-rot losses instorage. Cold storage temper-
atures hold back the development of the fungus, but cannot disinfect
the diseased fruits.

Pear rots with us are almost exclusively those which occur in
the orchard. The leaf-spot fungus (Zntomosporium maculaium Lev.)
also attacks the fruits of pearand may becomea source of loss in
storage. This applies more particularly to inferior grades of fruit.
Pacific coast fruit which is shipped to our district, may further
suffer from some of the ordinary molds which find access to the
fruit entirely through bruised or other injured areas.

The brief storage of quinces usually does not lead to much
further development of the quince rot. The fungus in question is
commonly the same as that in the apple rot, (Sphaetropsis malorum
Berk.).

STORAGE ROTS OF POTATOES, ONIONS, ETC.

With vegetables we have a very wide range of storage troubles.
In the case of potatoes we have two general types of rots, namely;
wet-rot and dry-rot. The wet-rot of potatoes commonly results from
two causes, viz.: The late blight or rot fungus (Phytophthora infes-
tans D’By.) may be expected to cause considerable losses of the
tubers in storage when these have been gathered from Phytophthora
infested fields and bacteria may cause rot ininjured tubers. In
Ohio, as stated under this disease of potatoes, the late blight and
rot fungus is not commonly prevalent. Perhaps little can be done
to preserve the tubers from such fields except to market the crop
promptly and to store with especial respect to the optimum con-
ditions. ‘The best temperatures for such potatoes will be warmer
than for apples, and it is very desirable that moisture be kept as low
as possible. 7

A wet-rot of potatoes, purely or very largely bacterial in cause,
must also be dealt with. This rot bacterium is different from the bac-
terium of potato wilt, (Bacillus solanacearum) and without the latter
may also induce considerable decay. It is believed the bacteria pro.
ducing this wet-rot gain entrance through injuries to the tubers
and that low humidity—dry storage—is especially desirable in keep-
ing down losses from this source.
364 OHIO EXPERIMENT STATION: BULLETIN 214

‘ Dry-rot of potatoes is due toafungus (Fusarium oxysporum)
which appears to belong among our soil infesting fungi. This
fungus appears to be the cause of. premature dying of the potato
plants and it certainly survives in the tubers from such infected
plants. At harvest time, asshown under dry-rot of potato, tubers
show infection at the stem end. Subsequently during storage the
fungus penetrates more deeply into the tubers and will often produce
dry-rot of the infected tubers. Further descriptive matter concern-
ing dry rot will be found in the special part of the bulletin under
potato. For storage of such infected tubers, as well as for the
general crop, it is desirable that storage temperatures be kept about
42 degrees Fahr., or slightly lower.

Sweet pobitoss also suffer from a large variety of rot troubles.
These sweet potato rots are more or less special in character and
since the crop is not largely handled in cold storage, nothing is here
offered in addition to what appears in the special part of the bulletin

ONION ROTS IN STORAGE

Onion rots area serious matter with onion growers and onion deal-
ers as well. It has been found that particular varieties of onions in our
climate are susceptible to special
diseases. For this reason we
must consider white onions such.
as White Silverskin, White King,
etc., ina separate class from the
rots of red and yellow onions such
as the Globe and Wethersfield
varieties.

With the white onions the
problem is partly a field problem
at harvest time, and partly one
of storage. The growers are in
the habit of gathering the white
onions before the tops fall and .
topping them immediately, in-
stead of throwing together in
heaps for absorption of the sub-

 

 

 

 

 

Fig, 27. A white onion that has been de-
stroyed bya blackneck or dry-rot fungus, Sc/e-

vrotium cepivorum Berk. This parasite has entered
the onion through the green neck which was cut
off at the time of harvesting the crop. (Froma
photograph by T. F. Manns).

stance of the tops by the onion
bulbs as is practiced with the
riper red and yellow varieties.

After topping the white onions
are placed in slatted crates, and these crates are stacked in the field
or in open sheds where they are kept dry. Often the loss from rot
during the six weeks following harvest may reach 60 percent of the
DISEASES OF CULTIVATED PLANTS 365

cro and as shown by investigations in Connecticut and our own
state, it has not always been clear why these losses are so large.
Recent investigations by this department lead us to believe that the
green onion neck of white onions handled in this way affords entrance
for the organism of the rot.

The sclerotium rot (Sclerotium cepivorum) appears to be the
most serious, although smudge or anthracnose of the onion ( Vermz-
cularia circinans) may sometimes cause large losses. Both these rots
are described under diseases of the onion. The writer believes the
Sclerotium rot is the larger criminal, and that both may be handled
by disinfection of the onions immediately after harvest. This dis-
infection may be carried out as described under the Maine formula
for Formaldehyde gas treatment, which is:

AN

Commercial 40 percent Formaldehyde.............: 3 pounds.

Potassium Permanganate crystals..... .........- 23 ounces.

Sufficient for 1000 cu. ft. of space occupied by crates or
trays. (See page 360).

The object of immediate disinfection is to prevent the entrance
of these organisms, particularly the sclerotium rot, through the
green neck of the newly topped onions. The exuding juices offer
favorable culture conditions for the fungus to develop.

When no fumigation is practiced following harvest, the onions
which are found to be sound and delivered for storage at the close of
the season may very profitably be treated in this way before winter
storage. Both these rots are essentially dry-rots of onions. In
addition, sometimes, we have wet-rot of white onions which may be
either due to bacteria or to the same fungus as the wet-rot of Globe
or other onions mentioned below.

The rots of yellow and red onions are of both the wet-rot and
dry-rot types, but the wet-rots are much more serious with these
varieties. Doubtless, as in all vegetables held foralong time in
storage, we have many cases of wet-rot in onions where some of the
common decay bacteria are the chief cause. These find entrance
through wounds, as in topping, and, under conditions favorable for
their development invade the tissues of the onion and cause decay.

In addition however, to the wet-rots due to bacteria of unde-
termined ‘species, we have a specific wet-rot of onions due to
Fusarium species. This wet-rot fungus belongs to the same group

_as the potato dry-rot and is liable to infect soils in which onions are
grown year after year. Rotted onions will show external develop-
ments of the pink fungus and may be detected in that way as well as
by use of the microscope. The chief factors of control with onions
of this kind, are in the methods of culture followed to produce the

crop.
366 OHIO EXPERIMENT STATION: BULLETIN 214

Dry-rot of red and yellow onions is rather rare and is commonly
referable to the anthracnose or Vermicularia dry-rot fungus
described under white onions. The best temperatures for onion
storage are about 38 to 42 degrees.
SPECIAL PART II

DISEASES OF OHIO PLANTS. ARRANGED ALPHABETICALLY
ACCORDING TO HOST PLANT

ALDER

Powdery Mildews. The alder suffers from several powdery mildew fungi on
the leaves (Phyllactinia suffulta Sacc., Erysiphe aggregata, (Pk.) Farl.,
Microsphaera aini (DC) Wint.) These retard development as with other leaf
coverings. Alder may also suffer from two or three leaf infecting diseases such
as an anthracnose and a leaf-spot. We have as yet little data concerning other
occurrences owing to the neglect of the study.

Stem Biights. From England an interesting branch parasite (Dztopella
fusispora De Not) has been reported by Plowright. This may or may not as
yet occur with us.

Root Tubercles. These root developments on the alder and some other woody
plants are commonly described as Mycorhiza, The particular organism ( Frankia
alni Nor.) has attracted a good deal of attention from students of forest problems
in Europe. Investigations of such growths upon the roots of our woody plants is
very much needed at this time in Ohio.

ALFALFA--LUCERN ~

Anthracnose. Twonew anthracnoses have been discovered attacking alfalfa;
the first of these, Colletotrichum trifolii B&E, so far as we know occurring
exclusively on plants of this family, the other, Colletotrichum sp., occurring only on
alfalfa in northern Ohio. The first one, which we may call clover anthracnose,
was discovered in Tennessee and has appeared upon alfalfa as well as red
clover in the southern portion of Ohio. It is less prevalent on alfalfa than upon
the red clover. Up to this time this disease has not been discovered upon either
host in the northern half of the state. The second anthracnose occurred recently
upon alfalfa from Sandusky and Carroll counties and has not been described.
Both of these diseaseses Show as a specific lesion or diseased spot on the stem or
leaf-stalk in the advanced stages of attack. Following this the plants wilt or
die and are discovered in this way. The disease is tuo new with us to measure
its injuries directly. To the writer it appears less serious than the dodders or
the root-rot troubles.

Bacterial Blight.(Yellowing). A bacterial blight of alfalfa, of which the
causal organism has not been definitely determined, has been reported from
Colorado where it appears to be spreading. In 1907 and to a still greater extent
in 1908, there was much complaint of general yellowing of leaves of second crop
alfalfa in Ohio and adjoining states, even extending to North Carolina. The
symptoms were general yellowing of this crop. With brighter, drier weather
later the next succeeding crop was of normal color. Bacteria have been found
by the Assistant Botanist in connection with this trouble in specimens from
eight localities and from four different counties in Ohio during 1908 and 1909.

Downy Mildew. The downy mildew fungus (/eronospora trifoliorum D’By)
has occurred in Colorado, and is very liable to occur in our state. No sugges-
tions can yet be made as to its prevention

Leaf-Spot Fungus. This forage plant is grown in parts of Ohio. It is attacked
by the leaf-spot fungus ( Pseudopezia medicaginis ( Lib.) Sacc.) which is found upon
both leaves and stem. Thesmall dark spots produced by it are easily seen. In

(367)
368 OHIO EXPERIMENT STATION: BULLETIN 214

attempts to produce alfalfa seed at this Station, the fungus has stripped the
leaves and seed capsules befcre maturity. It is very likely to prevent success in
growing this seed in Ohio, though it is much less injurious to the forage crop
proper because of cutting at short intervals. ;

Root-Rot. The same parasitic fungus (Fusarium roseum Lk.=Gibberella
Saubinetit (Mont.) Sacc.) which attacks wheat in the form of scab and also red
clover, has been found killing out alfalfa at Wooster (See Bulletin 203). This
fungus may survive in stubble fields where wheat and oats have been grown.
It readily kills off the young seedlings of alfalfa and if the soil is not fully
prepared for alfalfa seedings, the root-rot may extend its work and further
destroy the stand. At present nothing better is known than adequate
dressings of lime, preferably raw limestone, for areas to be seeded, together with
their proper enrichment. At this time warning is given as to the possible
seriousness of this trouble in the future. While not specifically noted in America
another root-rot-fungus somewhat known on other crops (Rhizoctonia) has also
been reported upon alfalfa from France. Another root-rot fungus (Ozonium
omnivorum Shear) well known upon cotton, also attacks alfalfa in the southwest.
I believe this is not known to occur in Ohio.

Rust. Alfalfa suffers from a rust fungus (Uromyses striatus Schroet) and
while it may scarcely have appeared in Ohio, it is almost certain to do soin
time. Like the similar leaf diseases of red clover, it may have rather small
economic interest.

APPLE

Bitter-Rot or Anthracnose. In recent years this fungus (Glomerella rufomac-
ulans (Berk.) Sp. and Von Schr.) has been investigated and its survival in the
mummy fruits and cankered
branches proved. (Bulletin 40
Virginia Experiment Station;
Bulletin 77, Illinois Experiment
Station; Bulletin 40, Bureau of
Plant Industry). This bitter-rot
is also a ripe-rot, in common
with other anthracnoses. For Ohio
certain varieties are the chief
sufferers; one of these is the
Bentley Sweet grown in Belmont
county, another is the Rambo.
The disease develops in the later
season and it seriously impairs
both the eating and keeping
qualities. For its control the
destruction of mummy fruits and
Fig. 29. An apple attacked by bitter-rot. Aregular attention to branch cankers are

curved outline of the spores will be observed, the conidia necessary in addition to the ap-
of the fungus developing in concentric forms under suit- plication of sprays. Since we

able conditions. After Alwood. know the life history of the
fungus better it has been possible
to control the bitter-rot successfully under orchard conditions as the annual
sources of infection in mummy fruits and cankers have been mastered. In this
late spraying soluble sprays are used toward the end as with the black-rot of
the grape.
Black-Rot. The black-rot also at times called brown-rot, is apparently more
common in the orchards toward the southern portion of the state. The writer has
found it a serious matter to control the black-rot fungus ( Sphaeropsis malorum

 
DISEASES OF CULTIVATED PLANTS 369

Pk.,) which attacks both fruit and branches and is a bar to successful maturity
of Northern Spy, Smith’s Cider and some other varieties at certain times. It
also invades storage apples and this rot is the most universal one in ordinary
cellar storage. With varieties adapted to climatic conditions, methods of hand-
ling by sprays and destruction of cankers and mummy fruits should prove as
effective as with bitter-rot. Unfortunately the varieties which most commonly
suffer from black-rot are those growing beyond their safe range of conditions.

Brown-Rot. There is a rarer rot fungus (Sclerotinia (Monilia) fructigena
(Pers.) Schrt.) than that of black-rot, which also attacks the apple in some
parts of the United States. For our region it is little known on the apple and
probably less important than either of the preceding.

Brown Spot or Dry-Rot of Baldwin. Very frequent complaint is made of small
sunken spots in fine specimens of Baldwin and some other varieties. Internally
these sunken spots are dry and somewhat bitter, leading to general breakdown
of the apple. These spots have been referred toa particular fungus, (Phyllachora
pomigena (Schw.) Sacc.,) but the case is not proved. This internal brown
spotting also occurs in Northern Spy and in Fameuse, and we hear complaint
of losses from it. The causes of the internal spotting are probably the same in
all cases and must in part be regarded as physiological breakdown. New
Hampshire Experiment Station (Bulletin 45) succeeded in controlling the form
of this. dry-rot on Baldwin by the use of Bordeaux mixture. Some irregularity
in results from spraying for it have been recorded elsewhere.

Canker. These diseased conditions upon branches may oocur in the propaga-
tion of. bitter-rot, but are more commonly referable to the black-rot fungus,
(Sphaeropsis malorum Pk.,) or to the
blight bacterium (Bacillus anylovor-
ws Burr.) (See Bulletin 163, New
York Experiment Station and Bul-
letin 235, Cornell Experiment Sta-
tion) although other fungi are
common in Europe as the cause of
canker. Among these are species
of nectria. Probably the canker
due to the black-rot fungus must
contest with that due to the blight
bacterium for first place in Ohio,
and its control is interwoven with
the control of the black-rot on fruit.
Canker-like dying of the external
bark may, and sometimes does,
occur without immediate penetra-
tion to the inner bark layer or
injury to the branch. All these
cankerous developments are, how-
ever, a source of danger and call
for continuous watchfulness. The heme
conditions of the fungus attacks are Fig. 29. Apple branches attacked by canker.
those of possible rifts in the outer
bark followed by the localizing of the fungus development. Those for the blight
canker are more extended and include blossom spurs. (See twig blight and
pear blight). Itseems probable also that the power of resisting attack varies
with the vigor of the branches. Up to this time our remedies have been largely

   
370 OHIO EXPERIMENT STATION: BULLETIN 214

the general ones of germicide sprays with addition of scraping off loosened bark
where possible; for this purpose a dull tool is. preferable. Some forms which
might be called canker on young trunks and on older branches are in fact forms
of winter injury from freezing. Types of -branch cankers are somewhat var-
iable, but they are all matters calling for close attention.

Collar-Rot. (See Sun-Scald). |

Coyneum or Orange Leaf-spot. During 1908 and 1909 specimens of an orange
leaf-spot have been received, and a severe case of defoliation of apple trees in
town was reported from Stark county. This leaf-spot is a central, erumpent
pustule with an immediate border of orange yellow: this yellow area shades off
into dark color toward the green tissue. Hartley has reported, upon investiga-
tions of the fungus in this case, Coryneum follicolum, that it is not actively
parasitic. Possibly we have this fungus following something else, after the
manner that another fungus follows the black-rot leaf-spot described below. (See
also rust of apple).

Crown Gall. This disease is especially a nursery trouble of apple and shows
its effects by enlargements near the crown or upon other portions of the stem or
root. It is quite probably due tothe same organism (Bacterium tumefaciens
Erw Sm & Towns) as the olive knot or some other crown galltroubles. This is
decidedly an infectious disease which probably calls for inspection of nursery
stock, and for great care to provide against diseased trees. Cure of infected

plants has not been secured. There is great danger in endeavoring to grow
nursery stock upon land which was once infected with the organism.

Edema. An Edema or swelling of apple twigs has been described by Atkin-
son from New York (Cornell Station, Bulletin 61). This on closely trimmed
trees on over fertile soil.

Fly-speck Fungus (Lepfothyriun pomi (Mont. & Fr.) Sacc.) This obvious
fungus disease in ordinary seasons appears chiefly upon apples grown in low,

moist situations. Peck’s Pleasant,
Rhode Island Greening, Rome Beauty
and several other varieties have been
noted as affected by the Sooty Fly-
speck troubles which may be identical
asto cause. During wet seasons, like
that of 1896 and 1909, a few susceptible
varieties are liable to be spotted by this
parasite whatever be the location of
the trees. Aside from selecting high,
sunny situations for the apple orchard,
spraying with Bordeax mixture will
prevent this spot. (See Sooty Fungus).

Fruit Blotch. Fruit blotch is a re-
cently described fungus (Phyllositcta
solitaria, E.&E.) which causes a ser-
ious spotting of fruit in a number of
ways as described in bulletins of the
Illinois and West Virginia Experiment

 

Fig. 30, An apple attacked by the Fly-speck :
fungus. The sooty fungus is also abundanton Stations, so that we may expect it to

specimen as is usually the case. give trouble in Ohio. As indicated
the fruit is attacked by this spotting
and in addition the fungus produces small cankers on twigs. Scott has
recently shown that it will be fully controlled by three or four sprayings with
Standard Bordeaux mixture. (See Bulletin Bureau of Plant Industry).
DISEASES OF CULTIVATED PLANTS 371

Leaf-spot or Frog-eye. There is a common leaf-spot disease of apple trees in
which the dead spots show the presence of pycnidia. This troubleis really due
to the black-rot fungus (Sphacropsis malorum Pk.) but at times another fungus,
{Coniothyrium pirini Sacc.), comes in afterwards. In the later season the
second type develops in concentric areas to which the common name of ‘‘Frog.
Eye’’ has been given. Yet other forms of leaf-spot due to spray injuries also
occur, but are easily distinguishable from the two first named. It has been
shown that control of the black-rot fungus keeps the leaf-spot in hand, but early
treatments should be made.

Mold. A blue mold is very commonly associated with soft rot of apples in
storage. The fungus (Penicillium glaucum Lk.) is a very common one and may
be regarded as associated with the presence of decay or bruising, not as a first
cause of rot.

Mildew. The powdery mildew (Sphaerotheca mali (Duby) Burr.) often occurs
upon nursery growths of the apple and occaionally upon rather thrifty growing
young trees. The dense felt-like covering of the fungus is usually very apparent
and the spreading of the fungus upon the foliage is sometimes noticeable. Spray-
ing with fungicides usually keeps the trouble in check.

Rust. The bright orange growths of this rust fungus (Gymnosporangium
macropus Lk., etc., I) are occasionally found on cultivated apple leaves as well
as on leaves of wild thorn apples, especially where these are within reach ofthe
cedar trees which bear the cedar apples. In 1909 the rust attacked apple fruits
in Ohio and Nebraska. These so-called cedar apples are no more than the
development of the rust fungus from which the spores are spread to the apple,
Crataegus, etc. A remedy in indicated by this statement, viz., get rid of cedar
trees. 7 :

Root-Rot. Serious root-rot troubles have been reported to us from Missouri,
Arkansas and Oklahoma where orchard plantings have been made quite soon
following the clearing of scrub oak, etc. Similar cases have been studied in
Ohio where plantings were made soon after the removal of the timber, especially
of oaks. One is usually able to identfy the rhizomorphs of the root-rot fungus,
(Agaricus melleus L.. (Armillaria mellia) and the characters by the occurrence
upon orchard trees and also the original growth is usually quite clear. Any
inadequacy of drainage is very serious in connection with root-rot. (See root-rot
of peach, etc.). More recently Von Schrenck has identified another fungus
(Thelephora galactinia Fe.) with a form of root-rot which shows no superficial
symptoms until after the tree is dead; it then shows the orange, leathery sheets.

Scab. Apple scab fungus ( Venturia inegualis Aderh, Fusicladium deudriti.
cum (Wallr.) Fuckl.) is a common source of large losses in Ohio apple
orchards. It attacks first the leaves and afterwards the young fruit, causing it
to drop. Aside from injuring the salability of the crop obtained and reducing
the vigor of the tree by reason of its attacks on the foliage, scab may prevent a
crop altogether because of this dropping of the young apples. The Ohio Station
was in the vam of progress in studying this disease, and the work has been
steadily followed (Bulletin Vol. IV, No. 9, (1891) B. 79, (1897) B. 111, (1899).
Full details may be found in the various bulletins given. Apple scab develops
when moisture is abundant during the early months of she season, and low
temperatures are usually prevalent at such times. The dropping of apples often
attributed to lack of pollination seems more often to be ascribed to the work of
scab. All varieties are attacked by scab but some suffer more than others.

ee
372 OHIO EXPERIMENT STATION: BULLETIN 214

The profit from spraying for scab on the apple (including apple worms)
has generally been large, because of saving the amount of crop and enhancing
its market value at the same time, as well as increasing the number of crops. In
this way the crops of a single orchard have been sold for a gain of about $1000
on an expenditure of $125 to $150. At the Station this gain has amounted to
$5.00 per tree (B. 111). The best fungicide for this purpose is dilute
Bordeaux mixture, or Bordeaux I of the spray calendar, containing 4 pounds of
sulfate of copper and 4 pounds of quicklime to 50 gallons of mixture with water,
or Bordeaux mixture and Iron Sticker consisting of 2 pounds of copper sulfate,
and 2 or 3 pounds of iron sulfate in 50 gallons of water. The Bordeaux
mixture and Iron Sticker has given better results in a rainy season like 1909.
The first spraying should be made just before the blossoms open, and upon the
young leaves, and the second after the blossoms drop, with additions of
arsenites in the second and in a possible fourth spraying as stated in the spray
calendar.

 

 

 

 

 

Fig. 31. Young apples attacked by the scab fungus (Venturia inequalis Adeh).

Scurf. The branch scurf fungus (Phyllosticta prunicola Sacc.) is believed to
occur in Ohio. This causes roughening of the bark, but no statements can now
be made as to its possible seriousness.

Sooty Fungus. The sooty fungus (Phyllachora pomigena Schw.) is often
associated with the fly-speck fungus, previously described, and is the more
unsightly trouble of the two. In most seasons the fruit in low situations is
DISEASES OF CULTIVATED PLANTS 373

liable to be rendered unsightly and unsalable by the spots which are illus-
trated in Fig. 32. In seasons like that of 1909 the disease may appear on
unsprayed trees in practically all situations. It was found in comparative
tests of Bordeaux mixtures and self-boiled lime-sulfur for apple scab and other
fungi, at the Carpenter test farm, that the sooty fungus appeared on the fruit on
the lime-sulfur trees. It is
thought by several that this
fungus spreads upon the fruit
after itis stored and at whatever
time it appears it renders apples
dull, unsightly and ‘unsalable.
Bordeaux mixture or its modifi-
cations may be relied upon to
hold the fungus in check. One
spraying at the time the apples
are the size ot hickory nuts may
prevent nearly all of the injury.
Upon varieties like Maiden’s
‘Blush, Grimes and Belmont the
spraying should be done a little
earlier than just stated. The
demonstrations by the Station
all over the state, show clearly
what improvement the spraying
makes in the apples where this
trouble prevails.

Sun-Scald, Collar-Rot. There
is frequent complaint of the
dying of the trunk of both young-
er and older apple trees wherein
there appears to be associated
the exposure to sun and the
death of the bark of the. trunk
upon younger orchard trees.
The freezing injury has been
carefully worked out in recent
years and is discussed under

 

 

  

be

 

 

 

winter injuries, with several Bice ee es
varieties of apples, notably the :
Grimes and King this trouble Fig. 32. Apples spotted by sooty fungus. The apples

is so serious over much of Ohio shown above were sprayed with Bordeaux mixture fol-

lowed by two sprays of Bordeaux and Iron Sticker. The
as to reduce the growth of these apples shown below were sprayed first with Bordeaux
sorts; while Murrill has sug- mixture and this was followed by two sprays.of self-
gested a connection between a boiled lime-sulfur. In neither case was the scab entirely
fleshy fungus and this dying of prevented. The lime-sulfur spray was not strong enough
the trunks of the King thé eon to keep offlate attacks of sooty fungus. From a photo-

graph by T. F. Manns.

nection has not been proved. The

injuries which occur on the south and southwest exposures of the trunk have
probably a direct connection with the danger from freezing injuries. Some
apparent sun-scald is.more probably due to the bacterium of pear blight as has
been recently proved by cultures from young trees by Waite. With Grimes
and other varieties susceptible to collar-rot caused by the bacterium ot
pear blight the only true relief is found by top working on some vigorous
sort such as Baldwin, Gano, and like varieties. ‘In the case of true
374 OHIO EXPERIMENT STATION: BULLETIN 214

sun-scald the effect of freezing is to form an ice layer and thus separate the bark
or inthe case of many water gorged cells to kill the sap layer. For further
discussion in this line see winter injury.

Storage Rots. These rots of the apple are extremely various since apples
infected before storage are liable to develop during storage the forms of rot due
to that infection. Even bitter-rot may not be overlooked in this way and much
more commonly still, black-rot and the rots which develop from the gradual
invasion of molds. It is found, futhermore, that bruises upon the apple or any
tendency to sun scald phenomona give dead tissues in which various saprophytic
organisms that normally hasten decay will do their work with rapidity. It is
understood, of course, that the temperatures of storage will regulate or control
more or less perfectly the rate of this development. Storage scalding of apples
is much worse in some varieties, notably in York Imperial than in the normal
toughened skin types. At present one can only suggest the rejection of those
sorts susceptible to scald for cold storage keeping.

Twig-Blight... This disease of the apple, caused by the bacterium of pear
blight (Bacillus amylovorus Burr.), is often very prevalent. The microbe enters
through the blossoms, being propagated in the nectar after infection by insect
visitation. It destroys the blossoms as well as small twigs of the tree. Beyond
the injuries just noted this microbe may gain entrance through the bark. (See
sun-scald). The twig injury is not very great from this cause cn the apple,
though the small dead twigs are unsightly. The prevention willlie in the
destruction of ali the blighted parts on apple, crabapple, pear and quince trees
in the vicinity. For fuller discussion see pear blight. In substance, this treat-
ment consists in cutting out all blighted portions in fall and early winter and
burning them to kill the resting forms of the microbe. It seems further that
well timed, early spring spray treatments on pear, etc., will cover up or destroy
spores of the blight. (See Circular 87).

Water Core. With the so-called Russian apples and occasionally with other
varieties as Yellow Transparent and Early Harvest, there are water core con-
ditions, at times, which may result in subsequent rotting. No explanation is
here offered as to cause for the condition.

Winter Injury (also called Sun-Scald). As previously mentioned there are a
number of evidences of injury which involve the trunks of apple trees of all
sizes; they are many times due to freezing injury; while this name winter injury
appears at the beginning of the paragraph and while the name sun-scald has
been applied for a long time to similar conditions, the injuries are directly due
to freezing, sometimes occuring in winter and sometimes, as in October 1906, due
to premature low temperatures. A conspicuous case occurred in the fall and
winter of 1906-7, more fully described in the bulletin devoted to these injuries (Bul-
letin 192). At that time as in other cases of injury from freezing, the low tempera-
tures accurred when the trees were gorged with water (sap). In the fall of 1906
we had very heavy rainfall with low temperatures so that there was stimulus to
excessive water absorption and no tendency to hasten ripening of tissues through
water loss and reduced water content such as occur in dry autumn periods.
The losses of young trees set one to three years, were very large in the winter
of 1906; indeed, in some cases there was practically a total loss as on slow grow-
ing varieties, notably the Rome Beauty in the Station plantation at Carpenter.
In general at that time the typical late variety of the northern part of the state,
Baldwin, and of the southern portion, Rome Beauty and the Hubbardson were
most seriously injured. It is evident that where we have such excessive water
supply in the inner bark and in the process of freezing, a layer of ice crystals
DISEASES OF CULTIVATED PLANTS 375

is formed. There is great danger of separation of the bark layer from the wood
at that time as at others. The sun exposed side seemed to have suffered worse
by reason of the more extreme temperature changes which were incited on these
exposures. Itis evident that warm periods in winter are a source of danger
when followed by low tem-
peratures.

Upon very large trunks
near the base, as on
Grimes and some others,
this may be the real ex-
planation of frequent sun-
scald or basal injuries.
Wherever such an injury
begins there is risk of the
intrusion of wound fungi
with all the consequences
which follow their en-
trance. The handling of
winter injuries Must so far
as prevention goes precede
the conditions which cause
it. Where possible the pre-
vention of excessive late
growth is desirable. In
cases of orchard trees it
may be that mulches of
coarse litter, especially,
will prove serviceable. It
may be added that this
injury to woody growths is
a less developed phase of
the killing back of herbac-
eous plants by the prema-
ture frosts.

Another phase still is e
ay gk Fig, 33. Johnathan tree, 4 years old, Southeastern test farm,
the killing back of branch- Carpenter, in cultivated portion. Tree of vigorous previous
es at the tips of woody growth with small lesion near base of trunk caused by freezing
growth which are not and sprouts from below. Photographed July 20, 1908. From

strictly hardy in our cli- Bulletin 192.

mate. In the case of our :

Japanese plum and of some ornamental shrubs, this is a frequent phenomenon
and its cause is to be sought in the same factors above described. Growth being
protracted late inthe season, these water gorged terminal twigs are killed
by the subsequent winter freezing whenever this is severe.

 

APRICOT

The apricot is rarely planted though occasionally is set in our Lake
Districts. The chief difficulties there have been the tendency to kill back.in
winter. Apricot foliage in addition is liable to be attacked by the similar leaf
parasites of peach and plum.
‘376 OHIO EXPERIMENT STATION: BULLETIN 214

ASH

Trunk Rots. The ash as a forest and shade tree is a vigorous grower, but
it is often marked by the attacks of timber decdys wheré these enter through
wceunds or by means of the bases of dead branches. We have urgent need for
more knowledge of these wound parasites.

Leaf-Spots and Rust. I may also state that the foliage of the ash is attacked
by rust (Puccinia fraxinata (Lk.) Arth.) but in the present state of our know-
ledge we are unable to apply effective remedies. This rust, as in the case of
other rusts, shows by the presence of its reddish or brown colored spore masses.
Of leaf-spot fungi there are a number which call for careful study.

ASPARAGUS

Anthracnose. An anthracnose fungus of asparagus (Colletotrichum sp.) is
. known in New Jersey but has not been frequent, if present, in Ohio.
Rust. In the east and in Europe the rust of asparagus (Puccinia Asparagi
DC.) proves to be destructive, and it has finally spread over Ohio.
; The rust causes appearance of unusually
early maturing of the plants. Closely examined
the rusted plants show blister-like spots on
skin of the stem, and underneath these ruptures
there is brown color due tothe spores. The
rust also assumes another form, the cluster-cup
stage, which may be found in éarly spring with
different color on volunteer plants; indeed the
aecidial, or cluster-cup, uredo and _ teleuto-
spore stages succeed each other on the stem.
The usual recommendations are to burn the
rusted bushes in autumn and to spray with
Bordeaux mixture; this latter ‘‘reduces the
amount of rust about one quarter.’’ (N. J., B.
129). The Leopard spot of asparagus stems is
apparently not infrequent, and the anthracnose
of asparagus, which produces very small specks
upon the stem, may also be expected, yet
neither of these compares with the rust in
Hes Ge. Raian Sein as destructiveness, nor does the rust of any other
rust. The rust causeselongated devel. Plant appear to surpass this in its ravages.
opment of the fungus, both upon the The Palmetto variety is reported less suscepti,
stems and leaves of the plant. ble to rust than any other sort.

 

AZALEA

Leaf-Spots. This plant is grown as an ornamental plant and whether in
hothouses or in protected planting out doors, is liable to injuries from leaf
diseases. One of these is a leaf-spot fungus (Septoria azaleae). It is also
liable to attack by a ‘‘bladders’’ fungus upon the young parts. 7

BARBERRY

Rust. Therust upon the barberry bush (4ecidium Berberidis Gmel.) is but
a form or stage, the aecidial or cluster cups, ofthe wheat rust (Puccinia gram-
ints P. rubigo-vera etc.). The increase of virulence in the rust of wheat and
rye, when grown near barberry bushes, was long noted before the demonstrated
DISEASES OF CULTIVATED PLANTS ~* ‘377

alternation of the fungus from the barberry to the wheat was proved -in our
century by DeBary. The barberry. hedge is objected to, at times, by adjacent
wheat growers, although we continue to suffer from the ravages of wheat rust
many miles from any barberry bushes. In the absence of barberry the rust
survives without it.

BARLEY

Rust. In the west and northwest there are two forms of rust; leaf rust
(Puccinia simplex (Koern.) Erikss. and Henn.) and stem rust (Puccinia gram-
inis Pers.). These rusts, like those of the other cereals, have not yet been
mastered or controlled.

Scab. Barley is attacked by scab (Fusarium roseum Lk.) in a manner
similar to that which occurs on wheat and rye. That the scab fungus is the
same for all grains has been shown by recent work of this department. (See
Bulletin 203).

Seed treatment for the loose spores and seed recleaning to get out the
shrunken and scab infested kernels ought to give favorable results. (See wheat
scab).

Smuts. The covered barley smut (Ustilago hordei (Pers) Kell. & Sw.) as
well as the naked barley smut (Ustilago nuda (Jens.) Kell. & Sw.) both occur
in Ohio, although barley is grown less extensively with us than in the west and
northwest. In the covered barley smut, the smutted heads more commonly
remain enclosed by the upper leaf sheath and a membrane holds the smut
masses, while the spores are exposed and freely scattered in the naked barley
smut.

The modified hot water treatment for loose smut of wheat has been found
effective upon the barley smuts. .See Farmers’ Bulletin No. 75, Yearbook
U.S. D. A., 1894: Spray Calendar, Bulletin 199.

5 BEAN

Anthracnose. The anthracnose of the bean causes unsightly spotting of both
pods and growing organs and is referred to the anthracnose fungus (Colletotri-
chum Lagenarium (Pass.) Hals.). This species is also regarded as the same one

-that attacks curcurbits, including cucumbers, watermelons, muskmelons and
gourds. The spotting of the bean pods is looked upon, too commonly, as a
natural phenomenon. Measures looking to its prevention have not found ready
application by growers. That fungicides are effective in reducing it we have
reliable testimony (N. J. Exp. Sta. B. 108). The recommended treatment begins
by soaking the seed 1 to 2 hours in ammoniacal copper carbonate, 1 ounce of
copper carbonate to 1% gallons of water. Bordeaux mixture is to be sprayed
upon 2 and 3 inch plants, followed by the same 10 days later, and again
repeated after blossoming of plant. The great thing to remember is that this is
a seed infecting disease. We must grow disease-free seed. (See Pea).

Bacterial Spot. A bacterial blight has been reported from New York (N. Y.
Exp. Sta. B. 181) and New Jersey (Exp. Sta. Rept. 1892) which promises more or
less injury. In this malady the diseased parts, leaves, pods, etc., show char-
acteristic, often watery spots. It is less prevalent on fresh land. The organ-
ism (Bacterium phaseoli Erw. Sw.) is widespread.

Downy Mildew. This fungus (Phytophthora Phaseolt Thaxter), so far as
known at present, has not been found in Ohio, though occurring to a destruc-
tive extent in the east, and liable to occur in our vegetable gardens. Experi-
ments have shown that it is controlled by spraying with Bordeaux mixture,
378 OHIO EXPERIMENT STATION: BULLETIN 214

(Conn. Exp. Sta. R. 1897, Pt. III). In this instance, as with the downy mildew
of cucumber, it is probable that August 1 is sufficiently early to begin the
application of the fungicides.

Powdery Mildew. Powdery mildew of the bean is due to the same fungus as
the powdery mildew of pea, for which see pea.

Rust. This fungus (Uromyces appendiculatus (P.) Lev.) is often observed to
produce reddish brown spore masses upon both surfaces of the leaves of beans.
It is perhaps rather more variable in occurrence, and certainly less injurious in
the past than bean anthracnose. It has been quite common in Ohio. Beyond
burning diseased refuse we are not prepared to suggest remedial or preventive
measures.

Stem-Rot. The root-rot fungus (Rhizoctonia) attacks the bean root and stem
and at times spots the pods in the south.

BEECH

Anthracnose. The anthracnose fungus (Gloesporium Fagi (Rob.) of beech
attacks the leaves, but is not so serious as many of the other anthracnoses.

Leaf Diseases. While the beech is not largely planted, it is nevertheless a
useful shade tree. The leaves are often attacked by two or three mildews (M/ic-
rosphaera erinophila Pk. & M. penicillata (Wallr.), also Phyllactinia suffulta),
which, however, rarely gives serious injury to foliage. In Europe the beech is
attacked by a rust fungus (/elampsora Fagi); the leaves are also attacked by a
leaf-spot species of Phyllosticta.

BIRCH

Anthracnose. The anthracnose fungus of birch (Gloeosporium Betularium,
E&M) attacks the leaves of our American birches while other anthracnoses are
known on the European species. Our knowledge of the injury is very limited.

Mildews. The downy mildews of beech and alder in part occur upon the
birches.

Wound Fungi. Characteristic flesh fungi invade pruning or other wounds in
the birch and are to be guarded against as with other woody growths.

BEET

Leaf-Spot. The garden beet is quite liable to the attacks of the leaf-spot
fungus (Cercospora beticola Sacc.) which causes serious impairment of leaf
action and premature dropping of the foliage. Other changes are likely to
follow those stated. This trouble may be controlled by the use of Bordeaux
mixture at fortnightly intervals. (B. 199). The leaves of beets are also attacked
by a white mold (Cystopus Bliti (Biv.) Lev.) although this latter fungus is less
frequent and less ruinous than leaf-spot. The same fungicide may be used if
required. See ‘‘sugar beet’’ for other diseases.

Scab. Thescab troubles on the beet are similar to those on the potato and
are referred to the same fungus. This trouble is likely to follow where beets
follow in soil that has been diseased with either beets or potatoes.

Root-Rot. (See sugar beet).

'

BEGONIA. (See Pelargonium).

Nematodes. These minute worm parasites attack the roots and also the
leaves of cultivated begonias (Ohio Exp. Sta. B. 73; N. J. Exp. Sta. Rept. 1894).
For the commoner root injury avoidance isto be sought in the preparation of
the earth.

Root-Rot. The root-rot fungus of violets and tobacco Thielavia basicola
Zopf.) was found attacking the roots of begonia which suffered from nematodes.
Its general occurrence since the discovery upon tobacco and catalpa show that
it is capable of serious injury to the roots of these cultivated ntnnt~
DISEASES OF CULTIVATED PLANTS 379

BLACKBERRY

Anthracnose. The anthracnoses of blackberry and raspberry (Colletotrichum
venetum Speg.) are idential and are described under the raspberry.

Leaf-Spot. This disease is also common to the blackberry and the rasp-
berry, although the latter is less commonly attacked. This fungus (Septoria
Rubi West) is conspicuous upon the wild growth and upon the trailing dew-
berries; it produces, usually, small, light-gray spots in the leaves and yields to
treatment with the standard fungicides. (See Ohio Exp. Sta. B. IV, 6, and
B. 79).

Crown Gall. Is apparently of a similar contagious nature to that of the
raspberry.It is of like appearance, though the galls at the crown of the plant are
often larger. A plant once attacked is incurable, and offshoots from it appear
to be generally affected, thus calling for immediate digging and burning of all
the diseased canes and the abandonment of propagation from such plantations.
(See raspberry crown gall).

Red Rust or Bramble Rust ( Cacoma nitens Schw.) is a well known disease of
the wild and cultivated blackberries, which also attack raspberries. It causes
the affected leaves to turn first yellowish in color, remain erect in position, and
finally to become bright red with-an abundant coating of the spores of the rust
fungus. These spores are readily scattered and may thus affect previously
healthy plants. The threads of the rust fungus (mycelium) live year after year
in the affected plants. For this reason the only remedy is to dig and burn all
members of the rusted stools. (See Bulletin 79). :

Root Diseases. Recent examinations of blackberry plantations show root
diseases of undetermined cause. The affected roots show brown spots as if
parasitized and the growth is seriously curtailed. Recent conditions in black-
berry plantations indicate root parasites since sections of the roots become
discolored and the growth of the canes is checked. These have not been suffic-
iently investigated for exact determination at this time.

BLUE-GRASS

Anthracnose. In the summer of 1908 the anthracnose fungus of wheat, rye,
oats and other grasses ( Colletotrichum cereale Manns) was discovered on blue-
grass in Ohio. This shows as black spots on the stems and basal sheaths, and
will evidently survive on this pasture grass. The injury is greater upon wheat,
rye, oats and clover, under which illustrations are given, than upon blue-grass.

Bacterial Blight of Head. In a recent bulletin from this department
(No. 210), Manns has described the organisms of blade blight in oats and has
reported a head blight in blue-grass and timothy caused by them. In this case
the bacteria appears to enter the upper sheath and cause a lesion above the
upper joint. This ends in the death and the drying up of the heads.

Powdery Mildew. The foliage of the blue-grass is attacked by the conidial
stage of the wheat mildew (Zrysiphe graminis DC). This fungus gives little
evidence of injury, though its presence is certainly of beneficial and the
perithecia of the parasite are not common on this host.

Rust. Blue-grass is likewise attacked by a rust (Puccinia graminis) which
is general on grasses.

Smuts. A smut fungus (Ustilago striaeformis West.) attacks the blades of
blue-grass though it is possibly not often very injurious.

BROOM-CORN

Smuts. Of these there are two, head smut (Ustilago Retliana Kuhn.) and
grain smut (Cintractia Sorghi-vulgaris (Tul.) Clinton), the latter of which is pre-
vented by treating seed for 15 minutes in hot water at 135 degrees F. and drying
380 OHIO EXPERIMENT STATION: BULLETIN 214

for planting as for oats. The same smuts attack sorghum and are very likely
to occur in foreign seed. (See Kansas Experiment Station Bulletin 23; Ills.,

Bulletin 47).
BUCKWHEAT

Leaf-Blight. This well known plant is frequently attacked by a leaf-blight
fungus (Ramularia rufo-maculans Pk.) which produces whitened areas on the
under leaf surfaces and causes dying of these leaves. It is not known to be
sufficiently destructive to warrant treatment for prevention.

Another leaf trouble referred to a fungus (Fusicladium fagopyri) is reported
from Europe, but is not known in our climate.

CABBAGE-CAULIFLOWER

Brown- or Black-Rot is a serious disease of these two crucifers, and attacks
others of the family, including turnips. It is a veritable scourge to the cabbage
growers of Ohio and other states. Smith (Farmers’ Bul. 68, U. S. D. A.) has
published concerning it and has a‘tributed the disease to aspecific germ (Bac-
terium campestre (Pam.) Erw. Sm.). The diseased heads may be dwarfed, in
portions rotted, and brown colors will appear in the woody layers of the plant,
including the stem. Badly diseased heads emit a penetrating and offensive odor.

 

Fig. 35. Young cabbages partially affected with club-root The club-root
survives in the soil and causes swellings and abnormal forms of the roots,
After Halsted, Bul, 98, N. J. Exp. Sta,
DISEASES OF CULTIVATED PLANTS 381

The losses from the brown-rot have been very large and specific remedies
cannot be stated. The author quoted sums up the subject of treatment
in one word—prevention. The measures recommended are—plant on new land
and only from healthy seed beds; avoid
succession of the same crops; avoid
stable manure and give preference to
artifical fertilizers to escape possible
infection through the manure. Prevent
animals from cropping in diseased
fields. Clean tools by scouring bright
after use in infected soil. Fight the
cabbage insects, since these inoculate
healthy plants with the disease.
Removal of badly affected plants, or
newly infected leaves, at intervals,
and subsequent burning or deep pitting
of this refuse may aid in checking
brown-rot. Destroy all mustard
weeds. See page 318 for part played
by water pores in the infection.

Club-Root. Club-root fungus (Plas-
modiophora Brassicae Wor.) attacks
these plants as well as the turnip, ruta-
baga, wild shepherd’s purse, hedge-
mustard and certain other plants of
the mustard family. It is called finger
and toe disease in England. It causes
enlargement of the roots and prevents
growth of normal head or root. (See
figure, p. 380).

This fungus is harbored in the soil,

so that if the land is once infected the
disease may prove lasting. It has not
yet been learned how long the trouble
will survive if the soil is planted in Rig@h Geb baesaisubenacten ey ented
other crops. Lands newly brought wilt. This has caused the leaves to yellow and
under cultivation may be infected with drop and the plant has produced no marketable
club-root through the wild mustard heads. The lesion caused by wilt fungus may be
plants upon them, Tt would appear serves soon Se lang se oper tal
possible by watchfulness to avoid
getting the club-root fungus into cab-
bage lands; the seed bed should be most carefully guarded from this trouble as
from rot. It will be much cheaper to abandon the crop for some other, when
the plant bed has become affected with club-root and the seedlings have
enlarged or whitened roots from this disease.
“In New Jersey, Halsted has investigated this trouble and has found (N. J.
Exp. Sta. B. 98 and 108) that fresh stone lime, if applied at the rate of 75 to 80
bushels per acre upon freshly plowed land in spring, and worked into soil, will
very greatly reduce the amount of club-root on turnips and cabbage; there is no
reason to doubt that this treatment is applicable to all plants of the order
attacked by club-root.

 

 

 

 

 
382 OHIO EXPERIMENT STATION: BULLETIN 214

Downy Mildew (Peronospora parasitica DeBy.), Leaf-Blight (Macrosporium
Brassicae Berk.) and White Rust (Cystopus candidus (P.) Lev.), occur upon the
mustard plants, including, perhaps, all named above and some others. As yet
their presence has not proved a serious drawback. If to be treated, Bordeaux
mixture should be applied.

Wilt. The fusarium wilt disease earlier reported from the eastern truck
districts, is now very destructive in Ohio. In 1909 it locally destroyed nearly all
the crop where either infected plants were set upon fresh soil or plants were set
on infected soil. It causes a yellowing and wilting of the plants sometimes
with apparent stem injury. In our cabbage districts it may be this wilt is to
contest with black-rot for first placein rank of injury done. The remedy lies in
breeding wilt resistant strains of cabbage.

CALLA

A Root-Rot of callas has been studied by Halsted and Townsend. The
disease appears to be due to bacteria (N. J. Rept. 1893). Reject rotted roots.

CARNATION

Bacteriosis of carnations has been reported upon by Arthur and Bolley (Ind.
Exp. Sta. B. 59). This causes many small, brownish spots with yellowing of
the leaves of the affected plants. Such are feeble in growth and deficient in
return. The maintenance of best and most favorable growth conditions may
often be effective in preventing this trouble; particularly sub-irrigation and war
on aphides are to be recommended.

Bud-Rot. A serious rot of carnation (Sporotrichum antrophilum Pk.) is
reported from several states and is doubtless present in Ohio.

Leaf and Calyx Mold (Hederosporium echinulatum (B.) Cke.) (Fairy Ring) of
carnations is often very unsightly upon the calyces and pedicels of these flowers;
it also attacks the leaves. All sorts appear to be more or less parasitized with
the fungus in the houses where it prevails. Yet another spotting is produced
by the carnation leaf-spot fungus (Sepfori Dianthi Desm.), which has appeared
at this Station more frequently upon the Daybreak variety. It is believed that
both these fungi will yield to treatment with Bordeaux mixture as per calendar.
(See Bulletin 73).

Carnation Rust (Uromyces caryophyllinns (Schrk.) Schroet.). This rust
fungus is one of the serious diseases of the carnation. There is some differerence
in the liabitity of varieties to the disease, and perhaps a much larger difference
in the condition of the stock plants from which cuttings are made. Assuredly
this matter of ‘‘cutting stock’’ is of very great im portance and one admitting of
selection of the very best plants. Experiments conducted at this Station in 1896
by the writer and the Station Florist (See B. 73) yielded no gain from spraying
with Fowler’s solution, which has been sometimes recommended. Watchfulness
in the destruction of rusted parts, and in the stock for propagation, are
suggested for the control of rust.

A Root- or Stem-Rot (Rhizoctonia and Fusarium) of éarnations has been
noted by Stewart (Bot. Gaz. XXVII, 129, 130) and occasional rotting of the
flowers through the presence of a Botrytis. For the former no thoroughly
effective remedy is now at hand, while general cleanliness of the house is
necessary to avoid the rot fungus Botrytis. (See Lettuce Rot). ;

CANNA

Rust. Foliage of canna is sometimes attacked by arust which may be
identified by the characters of its fungus (Uredo cannae).

CANTALOUPE
See Muskmelon.
DISEASES OF CULTIVATED PLANTS 383

CARROT

Leaf-Spot. This spotting of carrot leaves is usually caused by the same
fungus (Cercospora Apii Fres.) as the celery leaf-spot. Upon the carrot the
trouble is not usually serious.

CEDAR

Cedar Apples or Cedar Rust. During the showers of April, May or Juue,
large or small, jelly-like masses, often one amok or more across, with firmer
wood-like centers, are frequent upon
red cedar trees and upon similar
related plants. Microscopic exam-
inations of these jelly masses show
that they contain the spores of arust
fungus (Gymnosporangium macro-
pus Lk. and other species of Gym-
nosporangium). This fact need not
startle us but for another, namely,
that this is the completed or teleu-
tospore stage of a rust which may
seriously injure the leaves of the
apple. The apple grower will run
some risk then, in having about him
diseased cedar trees. The remedy
lies in the destruction of the cedar
trees.

 

CATALPA

Leaf Blight. Leaf blight of
catalpa has recently been trouble-
some to growers and puzzling to the
Pathologist at times. The sudden
blackening and dying of the leaves
in early summer has beén traced to
frost, but other times in later sum-
mer to root-rot, which see. Fre-
quently we have found a leaf blight
fungus (A/lternaria sp.) which devel- . %
oped freely upon the spotting leaves - — Scie
and appeared to be responsible in Fig. 37. Cedar apples caused by rust fungus.
conjuction with some other rather In May these dry looking apples send out jelly-like
unfavorable conditions for theyoung __ branches filled with spores of the rustfungus. These
trees. This will probably give more spores may attack leaves and fruit of apple, as well as
pi crataegus and juneberry, (From a photograph by
trouble in the culture of the catalpa wp. Beeching). ;
than the leaf-spot or mildew which
have been known much longer and prove less serious. Early applications of
Bordeaux mixture repeated at moderate intervals should check the disease. *

Leaf-Spot. The leaf-spot (Phyllosticta Catalpae E. & M.) is quite frequent upon
the leaves of catalpa. It rarely causes more than occasional spots in the leaves,
the injury being in no way comparable to that caused by the catalpa midge.
Fungicides should be effective against the true leaf-spot.

Mildew. The leaves of catalpa are often covered over by the powdery
mildew fungi (Microsphaera elevaia Burr., Phyllactinia suffulta Reb.). These
mildews tend to become conspicuous by the white covering upon the leaves in
later summer. While unsightly the injuries are rarely serious.

 

 

 
384 OHIO EXPERIMENT STATION: BULLETIN 214

Root-Rot. Since the recent demand for seedling trees of Catalpa speciosa,
some difficulties have been met with in diseased seedlings of catalpa. These
seedlings are liable to be attacked in their early stages by the ordinary damp-
ing off fungi such as Rhizoctonia, Pythium and Botrytis. One interesting case
of a true root-rot fungus was studied in 1908. The seedlings were being grown
in land that has been used some years for truck gardening; the stand was cut
down very much and in later summer some of the seedlings, then afoot or more
in height, showed sudden dying and dropping of the leaves; this was found to be.
due to the root-rot fungus of the violet and tobacco (7hielavia basicola Zopft.).
This must have been quite serigus on the smaller seedlings. At the date of
study, September, only the smaller root branches were destroyed by it and the
larger ones seemed normal. The injury to these seedlings in dry weather was
enough to bring about leaf collapse due to reduced water supply. If this fungus
becomes very general it will involve soil treatment for such seed beds. It was
too soon to determine how serious it may be upon trees of larger nursery size,
although it is not greatly feared.

: CELERY

Black-Root, so-called, may be found on celery plants from seed beds. In one
instance such plants yielded growths which shortly run to seed and were
valueless.

 

 

 

 

 

a
Fig. 38. Celery leaf attacked by leaf-spot. Various troubles produce similar
spotting in celery leaves.

Leaf-Spot or Leaf Blight (Cercospora Apii Fres.) is a prevalent condition
upon celery plants. This is at times attributed to the fungus above named, or
others, and is also produced by other causes, as by excess of water devine
overflow and the like. During certain seasons the loss from thé leaf-spot or
leaf-blight troubles is very much greater than during others.

i This. is clearl
explained when the conditions giving rise to the — :

 

      
DISEASES OF CULTIVATED PLANTS 385

But this is by no means a common fact, and in some years there is much blight-
ing after the celery has been boarded up for blanching. Usually the fungus is
discoverable in diseased areas of the leaves. The use of fungicides, such as
Bordeaux mixture, is likely to prove beneficial, especially to protect the plants
in the seed bed until transplanted. (See Spray Calendar). While beneficial for
later applications in the field, so long as it is not clear that the fungus parasite
is not the only cause of blighting or leaf spotting, all possible conditions should
receive attention. Kinney (Rhode Island Exp. Sta. B. 44) has suggested that
the breaking down of the celery leaves arises from the methods of culture prac-
ticed, particularly the level culture, in which the water relations of the plant
are not in a natural state. He succeeded in preventing the blighting of celery
by mulching with celery tops in which there was a large supply of the fungus.
Mulching, especially during periods of prolonged drought, may thus prove
profitable. The identification of the particular fungus occurring in the spots
must, in each case, be made by the misroscope. Aside from the mulching sug-
gested the remedies are stated in Bulletin 121.

The conditions of celery culture are yearly becoming more troublesome and
are really serious.

 

 

 

Soph cA SL aR ectea.

 

 

 

Fig. 39. Younger celery plants attacked by root-rot. These plants are kept alive by new roots,
though they increase but little in size. After VanHook, Cir. No. 72.

Heart-Rot is a very destructive decay of the inner, or heart, portions of the
celery plant after blanching has begun. The inner parts rot very suddenly,
emit a penetrating odor and the market value of the affected celery is destroyed.
386 OHIO EXPERIMENT STATION: BULLETIN 214

The decayed parts are teeming with motile bacteria to which this form of decay
has been attributed. The heart-rot prevails too in very hot, steamy weather,
but preventive measures are about all that can be recommended. It is suggested
that when the boards are first put up to the celery, under such conditions as
accompany the heart-rot, they should be left apart at the top and only closed up
to the usual point after an interval of several days. This secures better ventila-
tion and often prevents the disease.

Root-Rot. During a succession of wet seasons much trouble developed in
the Akron district from attacks of root-rot (Rhizoctonia). This gave trouble at
times with the seedling plants, but more seriously with the shortened develop-
ment of the crop. Often the roots were nearly all rotted off. Thetrouble seemed
to decline rapidly with drier seasons. (See Circular No. 72, Ohio Exp. Sta.).

Rust, true and false. In Europe the celery plant is attacked by one or two
rust fungi (Puccinia bullata (Pers.) and P. Castagnéi Thim.) of the same class
of parasitic fungi as those producing rust in wheat. These two rusts have not
as yet been discovered in America, though they will doubtless in time become
introduced. Celery which is banked in the earth often has the blanched stems
marked by rusty spots of various sizes. These spots appear to arise from the
contact of the stems with the earth, and on microscopic examination seem to be
due to the fungi or bacteria, or both, that may be present in the soil. The
difficulty is prevented by avoiding this method of blanching and substituting
boards or close culture planting. ‘

Bad Seed. There is scarcely’a more vital question in celery growing than
that of the quality of seed used. Seed that is of a bad strain though true to
varietal name, may inflict losses of hundreds or thousands of dollars on large
growers. Hollow celery, or that otherwise useless, according to present know-
ledge is very often due to the bad seed.

CHERRY

Black-Knot. This is a conspicusus disease attacking
the branches of cherry and plum trees but is more frequent
upon the cherry varieties of the Morello type. It is due to
a parasitic fungus (Plowrightia morbosa Schw.). Insects,
however, make harbors of the interior of the knots. The
spores of the black-knot fungus are ripened during the
winter and scattered in early spring, finding lodgement on
the new branches or in fractures on old ones, where their
growth causes the formation of anew knot. Black-knot
may be prevented by spraying with Bordeaux mixture, but
is more profitably controlled by carefully cutting off
affected parts and burning them, making a clean sweep at
least once each year and that previous to March rst. This
is a practicable measure and we have confidence in its
efficiency.

Leaf-Spot and Mildew. The first named disease is
Fig. 40. Twig of caused by the same fungus (Cylindrosporium Padi Karst.)

cherry attacked by as that which we call ‘‘shot-hole fungus’’ on the plum, and
black knot. This is the
summer condition May be successfully prevented by the use of Bordeaux mix-

wen one eer ae ture, except that only half the strength of mixture may be
surface and often give applied with safety to the foliage of the cherry. (See Cal-

inate ee a endar). The mildew is usually found chiefly upon sprouts

 
DISEASES OF CULTIVATED PLANTS 387

and young shoots. The mildew fungus (Sphaerotheceia Oxyacanthae (DC.) De By.)
is a very interesting one. This applies especially to amateur microscopic
study. If spraying is required for the mildew two applications will probably
be very satisfactory.

Cherry-Rot or Brown-Rot (Schlerotinia (Monilia)
Sructigena (Pers.) Schw.) affects all stone fruits,
including peach,
plum, apricot, etc.

It is by far the
most serious and
baffling of cherry
diseases to the
commercialcherry
grower. Thedecay
of the fruit is
caused by the
fungus named.
The conditions of
the season may
favor or retard
the spread and
development of the
fungus. The
threads of the
fungus (mycel- Fig. 42, Cherries, sound and rotted.
ium) survive inthe ‘The parasite in this case is the same as on
rotted fruits, other stone fruits.

Fig. 41. Leaf of cherry which may hang
attacked by leaf-spot fungus. Gy the trees unless removed. Careful removal of all
The dead areas in cherry - E
leaves turn dry and rarely give rotted fruit and spraying for the fungus, as per the
shot-hole effects. The same calendar, may be relied upon to save a part of the
fungus occurs upon the plum. fruit, but judgement and attention to the details of
From: Bulletini79. the work are always required. Itis to be under-
stood, also, that checking the curculio is a sure means of helping to check rot.

  

CHESS

Anthracnose. The anthracnose fungus (Colletotrichum cereale Manns.
attacks the chess as well as the cereals in which it may grow. The disease is
of interest upon chess because it may be a source of extending the development
of anthracnose. (See anthranose of oats, rye and wheat).

CHESTNUT

Anthracnose is a disfiguring spotting of chestnut leaves, about which
inquiries are often made. Small, dead areas with characteristic borders are
produced by this fungus (Marsonia ochroleuca B. & C.). Such applications of
fungicides as are made for shot-hole fungus of the plum and leaf-spot of the
horse chestnut, will be found useful when treatment becomes necessary on the
chestnut.

Bark Disease. A serious bark disease of chestnut in the east has recently
been described and has proved injurious. The fungus (Diaporthe parasitica
Murr.) appears to enter as a wound parasite through openings in the bark. It
has exterminated a part of the chestnut trees in the eastern half of Long Island
and about New York City. (See Yearbook, U. S. D. A., 1907, pages 489-490,
also Bulletin, Bureau of Plant Industry, No. 121, 1908). The beginnings of the
388 OHIO EXPERIMENT STATION: BULLETIN 214

disease show on branches with smooth bark, by the presence of dead, discolored
or sunken patches sometimes covered with the yellow orange or brown pustules

of the fungus.
CHRYSANTHEMUM

Leaf-Spot is frequently a disfiguring disease of this plant in earlier growth.
It is caused by the leaf-spot fungus (Septoria Chrysanthemi Cav.). Two other
fungi, a Phyllostica and a Cylindrosporium, also attack the chrysanthemum. For
indoor treatment copper sulfate solution of one fourth of the strength given in
the spray calendar—that is one pound to 50 gallons of water—will prove avail-
able. More applications will be required, but the foliage will not be rendered
so unsightly as with Bordeaux mixture which, however, may be applied in full
strength.

Powdery Mildew. Powdery mildew also occurs upon chrysanthemum foliage.
The fungus (Zrysiphe Cichoracearum DC.) is usually not persistent, but calls for
spraying foliage with fungicides when serious.

Ray Blight. A blight of the rays of chrysanthemum flowers due to a specific
fungus (Ascochyta chrysanthemi Cav.) is reported from the south and is very

: liable to be present
in Ohio.

Rust. This is found
on the chrysanthe-
mum, resembling
other rusts in its’
development. Rusted
leaves and _ badly
rusted plants should
be destroyed.

 

CLOVER
Anthracnose. Three

anthracnoses occur
upon clover; the
more common of
which is due to the
same fungus (Colleto-
crichum trifolii B. &
E.) as the anthrac-
nose of alfalfa, In
1907 it -attacked the
clover over the south-
ern one-third to one-
half of Ohio, causing
dying of the plants
attacked. These show
lesions of the stems
and leaf stalks and
may be detected in
the new seedings in
late summer through

 

 

 

 

Fig. 43. This shows clover plants from fields at the Station attacked
by new anthracnose fungus in 1909. This causes the leaves to droop and a
die; also at times the tips of the stems. From a photograph by T. F. the d ying of the
Manns. leaves of these plants.

It is not known how

serious this may prove upon clover, nor is this one known in northern Ohio.
The second anthracnose fungus (Glocosporium trifolit Peck.) has been
known longer than the first and occasionally shows by killing the tops of large
DISEASES OF CULTIVATED PLANTS 389

clover stems in meadows. It is apparently not a serious disease, althougha
very interesting one to study in connection with the anthracnoses due to
Colletotrichum.

The third anthracnose upon clover (Colletotrichum cereale Manns.) is the
anthracnose of wheat, rye and oats. It was found to a limited extent attacking
clover upon the Station grounds in 1909. Except in microscopic characters this
anthracnose cannot be distinguished from that of Bain and Essary first men-
tioned above. In the microscopic characters the two are clearly distinguishable.
It is quite probable that this fungus will be found over much of the state.

Black-Spot is due toa fungus (Phyllachora trilfolii (Pers.) Fckl.) which
attacks the leaves of clover causing dead spots and dark discolorations on the
under side of the leaves. As a rule these attacks come so late in the working
life of the leaves that the injury is slight.

Dodders occur upon clover as well as upon the alfalfa; with it, likewise,
there are two species (Cuscuta Epithymum Murr. and Cuscuta arvensis Beyr.), the
seeds of which are distributed in the clover seed. In 1907-8 when the domestic

- supply of seed ran so low the lack was made good by importations from Europe.
This has brought a large amount of dodder into the state, the most of it being
the clover dodder proper. With clover seedings as with alfalfa where infesta-
tions are slight it will pay to dig up by root the infested plants and burn them
for destruction of possible seeds. Dodder is a parasitic twining plant and may be
easily recognized by its appearance. The seeds are illustrated in Bulletin 175.

In the handling of the new clover seedings infested with dodder, ‘it is prob-
ably best to clip in fall to prevent ripening of the dodder seeds. The hay crop
may be cut the following season without fear since the seeds will not be in con-
dition to grow. Following the mowing of the hay crop it is probably desirable
to break the clover sod after the growth is fairly well started, and before time
enough has elapsed to permit ripening of the dodder seeds. In no case is it
desirable to cut seed from such dodder infested fields. Dodder in clover hay is
held responsible for scouring of cows and horses.

Leaf-Spot. A leaf-spot of white clover referable to an anthracnose fungus
(Ascochyta sp.) has been described from our region although not definitely deter-
mined in Ohio. The injury which may result cannot be now stated.

‘Rust. The various sorts of the cultivated clover, Red, Alsike, Mammoth,
etc., are attacked by a clover rust (Uromyces Trifolii (A. & S.) Wirt). If one
will examine the small, dark spots in the clover leaves he will find a cluster of
this reddish fungus beneath. This rust does not spread to other plants than
clovers and is commonly regarded as more disfiguring than destructive. It is
not nearly so injurious as the leaf-spot of alfalfa. which is similar in
appearance.

Root Nodules and Root Tubercles upon Leguminosae. Upon removal of the
roots of the clover plant from the soil one finds minute enlargements which are
the subject of frequent inquiry. These are nodules or tubercles as they were
“formerly called, caused by the messmate-living of certain nitrifying organisms,

_ or microbes, with the clover plant. To these microbes in this communal life is
due the power of withdrawing nitrogen from the atmosphere and fixing it in the
the tissues of the clover plants. The same applies in general to the nodules
upon plants of this order, the Papilionaceae. It thus follows that these nodules
are the normal condition of properly nourished leguminous plants of the order:
FPapilionaceae, and it likewise follows that the full value of this work of nitrogen
fixing is only realized for manurial purposes when the tissues of the clover
plants decay in the soil.
390 OHIO EXPERIMENT STATION: BULLETIN 214

Stem Blight of clover has recently been studied at the Station and has been
found to be due to the same fungus as that of wheat scab (Fusarium roseum Lk.).
This fungus has been found to cause the death of seedling wheat plants and to
follow harvest by attacks on clover stems. (See Bulletin 203). It appears at
this time to be one of the serious forms of clover sickness. The writer looks
upon it as liable to be much more
serious even than anthracnose. The
only present suggesion for control
will apply to control of the wheat
scab fungus through recleaning of
seed and separation of of all scab
infected kernels. It is quite likely
that clover seedings made in a dry
year with little grain scab will not
be exposed to the same danger from
this blight as those made in wet
seasons when the disease is very
bad inthe grain. (See wheat scab).

CORN

Bacterial Disease. This has been
described and illustrated in Bul-
letin 6 of the Illinois Experiment
Station, 1889. The malady infests
f both younger and older plants. In
i ( as j the younger it causes a yellowish

— LA coloring and a general appearance
; Fig, 44. Red clover stems suffering from stem of debility, with death of the leaves,
sickness. The grayish spores in the lesions are those :
of the fungus of wheat scab. From Bulletin 203, commonly from the point backward.
After midsummer, spots appear op
the exterior of the sheaths which are more conspicuous on the inner side and at
times more or less smeared with a gelatinous substance. No successful remedy
has as yet been proposed.

Dry-Rot or Mold. The dry-rot or mold of corn (Diplodia zeae (Schw.) Lev.) was
investigated by this Station in 1906, it being reported by a grower in Licking Co.
He stated that he had been studying the development for two years; the first time
noted, the mold area was small involving but part of one shock; the next year a
larger area had been invaded and the year of 1906 he reported his losses were
still greater. He reported that conditions clearly indicate the invasion of the
soil by the parasite and possible infection through the growing plant. Asin
this case from Licking county and many others in which continuous corn grow-
ing is practiced on rather moist soil, there is great danger from accumulation or
infection. The ears attacked were marked by adherence of the husk and the uni-
form moldy covering matted the kernels together upon the ear and destroyed the
feeding value.

In the matter of prevention little can be done beyond avoiding continuous
cropping of corn for invaded areas. For life history of the fungus see Circular
117, Illinois Experiment Station; 22nd Annual Report, Nebraska Experiment
Station, 1908.

The Leaf Blight Fungus (Helminthosporium graminum Rab.) has been noted
on corn and has recently been sent to this Station from Vinton county, in the
latter case upon sweet corn. The fungus causes somewhat extended, or elliptical

  
DISEASES OF CULTIVATED PLANTS

391

brown (dead) areas in the leaf blades, readily identified by the microscope. All
_ diseases of the young corn attract notice, but it is not certain that there is need
to apply fungicides for this fungus, though such might prove successful.

 

The smut boils
shown here later burst open and scatter masses of smut spores.

Fig. 45. Stem of maize attacked by smut.

or decays where the air circulates in contact with
silage. We have investigated the mofd fungus
(Penicillium sp.). This is possibly the same blue
mold which we have found to attack fruits in
storage and transit. It is not an active organism
and must be held in check by control of conditions
in the silo.

Corn Smut is a well known disease, attacking
leaves, shoots, ears, tassels and brace-roots of corn,
converting the diseased parts into masses of dirty
(smutty) spores of the fungus (Ustilago Zeae
(Beckm.) Unger ). A brief article upon corn smut
will be found in Bulletin 78. (See also Bulletin 92
of the Kansas Experiment Station). The corn
smut may be propagated by smutty seed, although

Corn Rust (Puccinia
Maydis Berang.) is met
with in greater or less
abundance upon corn every
season, the greater abund-
ance usually being in rainy
seasons. The rust causes
small oblong or elliptical
spots on the surfaces of
leaf and sheath and in the
spots are contained red-
dish-brown spores of the
rust. The shade of the
spores will vary with the
time and development of
the fungus. Here, as with
wheat, the fungus passes
through the uredo and
teleuto stages.

Silage Mold. At times
we have complaint of mold
in silos where corn silage
is stored. Doubtless there
is some loss in nearly all
cases from different molds

 

Fig. 46,
destroyed by smut,
may be found showing different
forms of attack,

An ear of corn partly
Other ears

much more likely to be carried by the transportation of the yeast spores
of this smut fungus which may light upon any young growing part and
produce smut infection. From this fact and from another—probably a greater
392 OHIO EXPERIMENT STATION: BULLETIN 214

prevalence of the smut yeast spores in later summer—later. growing parts, for
example, tassels, brace-roots, ears and sucker shoots, are perhaps more often
attacked by the smut. The smui spores may be scattered in manure if smutted
fodder is used, and it seems well proved that manured land yields more smutted
corn than unmanured. The same may be true of clover sod as compared with
corn stubble. The reason would exist in the decayed vegetable matter, wherein
the secondary yeast spores of the smut may grow and then may be carried to the
corn which becomes thus affected. Treatment of seed corn does not apparently
reduce the amount of smut. Cutting and burning the smut boils before they have
burst open would be useful. It is worth while to fight smut by all available

means.
COWPEA

Leaf-Spot. In southern Ohio where these are grown there is danger of the
leaf-spot (Cercospora). This is not liable to be very serious.

Wilt. The wilt fungus (Vecosmospora vasinfecta tracheiphila Erw. Sm.) is
more serious, although at present largely confined to the southern districts. For
Ohio conditions the practice of growing cowpeas is not of such extent as to
threaten seriously with this disease.

CRABAPPLE
Scab. The same scab which attacts the common cultivated sorts also attacks
the crabapple, including both fruit and foliage. The remedy is that given under

apple.

Rust. The same rust fungus
(Gymnosporangium macropus Lk.),
in the cluster cup stage appears on
the crabapple leaves and fruit as
well as upon the leaves and fruit of
apple, and leaves of crataegus. (See
Apple).

CROCUS

Root-Rot. Little study has been
made with us of the diseases of
bulbous plants, yet we are liable to
import those occurring in Europe.
The common root infesting fungus,
Rhizoctonia, is one of the determined
troubles of crocus in France. Micro-
scopic identification of the trouble
should be easy owing to the charac-
ters of the fungus.

CUCUMBER

 

Anthracnose (Colletotrichum
Fig. 47, Cucumber leaf and stem attacked by Lagenarium (Pass.) Hals.). This
Anthracnose. The dead areasin the cucumber leaf, fungous disease attacks nearly or
caused by Anthracnose, are usually larger and more it rl bi 1 th
nearly circular in outline than with downy mildew. quite -all curcur its as well as Ae!
bean. Upon the cucumberin Ohio
it is apparently more destructive during the earlier season. The fungus may
be found in the greenhouses at all cultural periods, as well as in the field. It causes
circular dead spots in the leaves, usually more than one-fourth inch in diameter,
and likewise elongated brown areas on the stem. (See Bulletin 73, 89 and 105)-
DISEASES OF CULTIVATED PLANTS 393,

Unlike the downy mildew, anthracnose may be checked after it appears, though
best prevented by earlier applications of the fungicide. In the field, Bordeaux
mixture is to be preferred; inthe greenhouse, copper sulfate solution, one pound
to 50 gallons, has proved efficient and has checked the anthracnose after one-
fourth of the plants had been destroyed by it.

Damping-off is a frequent trouble upon greenhouse cucumbers. It is serious
often where plantings are made following lettuce attacked by rosette. The
fungus in that case is the same as lettuce rosette (2hizoctonia) or lettuce drop
(Botrytis). There isa strictly damping-off fungus (Pythium De Baryanum
Hesse) that is sometimes troublesome. The Botrytis named at times attacks
pruned parts of cucumber plants, also extending its attacks to the blossom end
of young fruits. -

The results of Rhizoctonia on greenhouse cucumbers have been curious
owing to attacks on the smaller root branches or rootlets. The growth of the
vines is at times checked,
accompanied by coloring
of the leaves and reduced
“fruitfulness. Some grow-
ers have given the name
‘eaf-curl’’? to this phe-
nomenon but it is strictly
the effect of the fungus
named. It has been found
necessary in soiltreatments
where cucumbers follow
affected lettuce to increase
the strength of formalin
drench to 4 or 5 pounds
per 50 gallons of water.
{See Soil Diseases).

Downy Mildew. Downy
-mildew fungus (fPlasmo-
para Cubensis (B. & C.)
Humpbh. ) is late in its at-
tacks, not having been
found in Ohio fields earlier
than August 3rd. It causes Fig. 48. Cucumber leaf from greenhouse, attacked by Downy
angular, yellowish spots Mildew. The spots in the leaves caused by the mildew are
on the leaves, followed by usually outlined by the veinlets of the leaf.—From a photograph
yellowing of the whole leaf >¥ 7 F- Manns.
and death, as by frost. It spreads with extraordinary rapidity, requiring only
three or four days to become disseminated throughout a large field. Unlike
anthracnose, it may not be successfully checked after its appearance, and it is
not safe to leave untreated plots in fields to be sprayed. July 25th to August 1st
is sufficiently early to begin spraying for mildew, but applications should be
repeated at intervals of 7 or 9 days. In 1898 an increase of 75 bushels per acre,
of sprayed over unsprayed cucumbers, was obtained at Creston. (Bulletin 105).
Cucumber pickle growing finds in this mildew its most serious enemy. If any
of the crop is to be harvested after August 20-25 spraying with fungicides ap-
pears necessary. Early planting may permit gathering the crop before this
date. The downy mildew is also very destructive in the forcinghouse, and is to
be treated with the same fungicides recommended for anthracnose. (Bulletins

73, 89 and 105).

 
394 OHIO EXPERIMENT STATION: BULLETIN 214

Leaf-spot of cucumber is also due to fungi. (Phyllosticta Cucurbitacearum

Sacc. and Cercospora Cucurbitae E.&E.) Of- the two species named, the
Phyllosticta was the commoner in thrifty pickle fields in 1898; the Cercospora
being apparently confined to wet fields, though this cannot be expected to hold
true under all circumstances. The Phyllosticta was found almost exclusively
upon the unsprayed pickle plants and seems, therefore, amenable to the same
treatment as applied for downy mildew. (Bulletin 105).
Mosaic Disease of greenhouse cucumbers has been recently studied in Ohio.
This disease is analagous in character to the mosaic disease of tobacco and to-
matoes and to the yellows of the peach. It is due to an oxidizing ferment in the
leaves and is transmitted like the tobacco mosaic disease, by touching first dis-
eased and then healthy plants. The fruitfulness of these variegated yellow
plants is very low and it is best at all times upon the appearance of the disease
to remove the diseased plants and destroy them.

Nematodes or Eelworms (Hetervodera radicicola (Greef.) Mull.). These
minute parasitic worms are often very destructive upon cucumbers under glass,
They are especially soin some cases recorded in Bul-

letin 73. The greatest injury may occur on the seedling
plants, but plants of all ages ‘are destroyed by the para-
sitic worms. Their presence may be known by the
small, bead-like enlargements produced upon the roots
or rootlets. This matter is treated at some length in that
Bulletin. No remedy has been discovered that is effec-
tive with plants once attacked by eelworms. The time
to prevent this trouble is in the selection or preparation
~ or treatment of the the soil for greenhouse benches.
Indeed the nematodes seem to be present in old sod, and
to some extent in decaying vegetable matter generally.
An effective remedy against eelworms consists in steam-
ing and so treating the soil that the parasites will be
destroyed. For this procedure see calendar and Bul-
letin 73. Also Massachsetts Exp. Sta. Bul. 55, In thus
handling the soil due time must be given for draining
and drying.
Powdery Mildew (Zrysiphe Cichoracearum DC.) of
Fig. 49. Roots of seed- cucumbers is also frequent in the forcing house, but
ling cucumber with Nem- rarely destructive elsewhere. For this fungus a dilute
ae ca ie sla copper sulfate solution is effective. See Bulletin 73.
wae ep ty Root-Rot. The root-rot or so-called ‘‘leaf-curl’’
development on matured cucumber plants referred to
Rhizoctonia, is often serious. It is more fully discussed under damping-off above.

Spot of Cucumber Fruit or Cucumber Scab (Cladosporium cucumerium Ell, &
Arth.), has been reported upon cucumbers by Dr. Arthur (Ind. Exp. Sta. Bul.
19), and may prove injurious if prevalent. It should be found amenable to the
same treatment recommended for anthracnose and downy mildew.

Cucumber Wilts. The wilt diseases of cucumbers, likewise of other cucur-
bits, are a source of usual complaint in the earlier season, as the plants are
beginning to form vines. In 1899 these complaints continued much later. The
plants suddenly wilt down as from lack of water, then soon die. What has been
referred to the same general cause was also observed in the cucumber forcing-
house, apparently starting in the leaves. Smith (Proc. Am. Ass. Adv. Sci. 1893)
refers this disease to a bacterium (Bacillus tracheiphilue Smith) which is trans-

_ ferred from diseased to healthy plants by the cucumber beetle and the squash
bug. This form of wilt has been found on cucumbers, muskmelons and squashes

 
DISEASES OF CULTIVATED PLANTS 395

in Ohio. In addition we have found to a limited extent, another wilt disease of
the cucumber which appears to be similar to that described by Dr. Smith.
(Proc. Am. Ass. Adv. Sci. 1895, p. 190). On watermelons in the South he finds
a trouble with which ours may be identical. (Bul. 105, p. 222). This latter is
referable to a species of fungus, a fusarium (/usarium niveum Smith), which
grows internally in the stem and finally plugs up the water vessels in a manner
similar to the work of the bacterial wilt. Spraying is unlikely to be beneficial
for this wilt or for the bacterial one. Preventive measures suggest gathering
and burning infected vines, and especially waging a successful war against the
insects; these should prove more or less successful according to thoroughness of
work. The fusarium wilt calls for rotation of crops. Much may be finally done
by breeding varieties resistant to wilt.

CURRANT

Anthracnose. The anthracnose (Gloeosporium ribis (Lib.) Mont.) of the currant
has occurred occasionally and will apparently be checked by the same treat-
ment as given for raspberry anthracnose.

Cane Blight is a very serious disease whenever stools are attacked by it.
The fungus (Vectria cinnabarina (Tode) Fr.) survives by its threads in the
tissues of the stool and upon the death of the canes develops as a bright pink
mass of the fungus upon dead parts. While spraying may, and surely must,
keep down the risk of infection, whenever stools show attacks by dying of a part
of the canes and the development of this fungus these infected stools are doomed
and should be removed and burned.

Black-Knot. <A black knot fungus (Plowrightia ribesia Pers.) has been de-
scribed upon currant, and is always a possibility with us. It attacks the
branches or stems.

Dropsy. This disease has been met with. It causes very considerable en-
largement upon the young stems of the currants, not unlike in appearance the
enlargements due to crown gall in the peach, except that usually more of the
stem is involved than in the other case. The trouble appears to be due to physi-
ological causes and the pruning knife may. aid cultural efforts.

 

Fig. 50. Leafof currant attacked by leaf-spot. The dead areas are
easily seen in the currant leaf but the fungus is difficult to discover.
396 OHIO EXPERIMENT STATION: BULLETIN 214

Knot. This fungus (Pleonectria berolinensis, Sacc.) is a stem trouble of cur-
rants and calls for investigation. It has been collected in this state.

Leaf-Spot of currants is referable to two species of fungi (Septoria ribis
Desm.; Cercospora angulata Wint.) of which only the Septoria has been dis-
coveredin Ohio. (See Bulletin 79). These fungi produce early spotting and pre-
mature dropping of the currant foliage; in some instances the leaves drop even be-
fore the fruit has ripened. Bordeaux mixture applied as per calendar is effective
against this disease, though late applications may render it necessary to wash
the fruit. For this reason, if for no other, the first application should be made
very early and followed by about two more at fortnightly intervals. :

Rust. A rather common rust fungus (Puccinia ribis DC) has been discovered
upon currant. Warning has been recently sent out against a second fungus
(Cronartium ribicolum Dietr. Peridermium strobi Kleb.) which attacks the
seedlings of white pine in the aecidial stage, and passes its uredo and teleuto
stages upon leaves of currants and gooseberries. This fungus is to be sought
for with care since its occurrence in the United States may have much to do with
the success of forest plantings of white pine.

Powdery Mildew of gooseberries (Sphaerotheca mors-uvae (Schw.) B.&C.)
sometimes attacks currants where it is apparently less destructive than on
gooseberry. Reasonable spray treatments should control it.

DEWBERRY

Leaf-Spot. (Septoria rubi West.) Cultivated dewberries as well as the wild
sorts, are peculiariy susceptible to the attacks of the leaf-spot fungus. It causes
very small grayish spots inthe leaves. The same fungus attacks blackberries
and raspberries, as previously stated. It may be prevented by a careful appli-
cation of Bordeaux mixture.

Rust. The bramble rust also attacks the dewberry as in the case of ttack-
berry. For treatment see blackberry.

EGG-PLANT

Anthracnose. The anthracnose fungus of egg-plant (Glocosporium melongenae —
Ell. & Hails.) attacks the fruits of egg-plant and causes spots in them. ‘Lhis ;
occurs frequently in Ohio. These show early as pits in the surfaces of the fruit
which show the usual border.

Bacterial Blight. The common solanaceous blight organism (Bacterium
solanacearum Erw. Sm.) attacks the egg-plant as well as the potato and
tomato. Where attacks occur destruction of the affected plants is all that can
be done.

Fruit-Rot. A fruit-rot of egg-plant likewise occurs and may at times appear
as a leaf-spot fungus. This, like the anthracnose and leaf-spot, should yield to
treatment by sprays. Ammoniacal copper carbonate may be used tow2rd the
ripening period.

Leaf-Spots. Two or more leaf-spot fungi have been recorded on egg-plant
and will doubtless be found when sought.

Stem-Rot. The stem-rot fungus of sweet potato (Vectria ipomoeae Hals.) has
been described upon egg-plant by Dr. Halsted. The conidial stage is evidently 4
species of fusarium and it may or may not be a different one from that with
which we have to contend upon the potato; it is recorded by Dr. Halsted as the
same that occurs on sweet potato.
DISEASES OF CULTIVATED PLANTS 397

ELM

Bleeding. Bleeding of pruned elm trees is often annoying as well as
dangerous. Mr. Boddy, City Forester of Cleveland, thinks asphaltum covering
over cut surface reduces or cures the bleeding. This is successful when searing
by torch precedes application of dressing.

Black-Spot. The leaves of ornamental elms are attacked by black spots
( Dothidella ulmi (Duv.) Wint.) (Gromonia Ulmea (Sacc.) Thuem.) which some-
times injure the leaves, and by this means checks the tree. ;

Other Leaf Diseases also occur upon the elm. One of these is a leaf-spot
(Phyllosticta ulmicola Sacc.) which matures its spores in the fallen leaves.
Gathering and burning these infested leaves will prove a check on this fungus,

The Powdery Mildews (Microsphaera Alni D.C. and Uncinula macrospora
Pk., more often the latter) likewise attack elm leaves. If troublesome these
should be reached by applications of Bordeaux mixture, making the first
application when the leaves are half grown.

Timber-rots are also known onthe elm; to be guarded against in wound
infection of shade trees. /

Twig Disease. In portions of Ohio and in Kentucky a dying of elms which
are prized as shade trees has been reported. This disease shows first as'a loss
of leaves at the ends of twigs, often at the tops of trees. (See Kentucky Exp.
Sta. Bul. 84). Itis believed by Prof. Garman that changing soil conditions
have much to do with this disease. To the writer it would seem that the water
factor with this, as with many other shade trees, may prove a determining
cause. At any rate, the time has come for a study of these water problems in
shade trees.

EMMER

Anthracnose, Scab, etc. Emmer and its near relative, spelt are attacked in
Ohio by the Anthracnose (Colletotrichum cereale Manns) and by the scab
(Fusarium roseum Lk.) These diseases are the same as those occurring upon
rye, wheat and other cereals under which heads fuller notes will be given.
(Also see bulletin 203).

FIG

Leaf Diseases. The fig is frequently grown in conservatories and is often
attacked by leaf diseases. The commonest leaf fungus (Cercospora Bolleana
(Thuem.) Speg.) of the Mediterranean region is a serious leaf disease. The
attacked spots assume a brown color, the leaves eventually yellowing and drop-
ping off. Where leaves of fig begin to drop from such causes, a spraying with
Bordeaux mixture should be applied upon the younger leaves.

FILBERT

Black-Knot (Cryptosporella anomala (Pk.) Sacc.) has been found upon culti-
vated filbert or hazel-nut in New Jersey and Massachusetts (N. J. Exp. Sta.
Rept. 1892 and Mass. Exp. Sta. Rept. 1892). This is a serious stem disease
which may check successful culture when it occurs.

FLAX

Dodder. Flax is attacked at times by a seedling parasite, flax-dodder
(Cuscuta Epilinum Weihe) whose tiny, leafless stems wind about the flax plant
and by haustoria, or sucking organs penetrating the epidermis, draw from it
substances essential to healthy growth. The dodder seeds are carried in the
flax seed and prevention must seek to avoid the seeds.

Other Diseases of flax are noted to occur in the Northwest among which are a
Fusarium wilt and a Colletotrichum blight. (See bulletins 50, 55 and 71, North
Dakota Exp. Sta.).
398 OHIO EXPERIMENT STATION: BULLETIN 214

FOREST SEEDLINGS

Forest seedlings as will be noted under Catalpa, Pine and Spruceare
especially liable to certain disease attacks upon the young plants. The number
and variety of these diseases is scarcely realized until one begins to care for their
survival as in forést culture. It will usually be found in newly cleared areas.
used. for this purpose that the leaf mold is badly infected with seedling para-
sites. Some treatment of this soil before using as seed beds is desirable. For
some of the commoner damping-off fungi the formalin drench may succeed. For
coniferous seedlings, other treatments may be required. Recently the United
States Department of Agriculture has reported upon two methods of treatment
which consist of the use of dilute sulphuric acid, or mixtures of lime with
powdered copper sulfate. (See circular No. 4, Bureau of Plant Industry,
United States Department of Agriculture).

GINSENG

Leaf Blight or Leaf-Spot, (4/ternaria sp.) occurs upon ginseng plantations,
These have been checked at times by spraying with Bordeaux mixture, while at
other times the sprays being made immediately before cold weather caused
serious losses.

Root-Rot. The root-rot fungus (7hielavia basicola Zopf.) has been found in
New York by Van Hook to attack the roots of ginseng and cause destructive
rotting. This may prove a serious drawback to ginseng growing, and methods
of prevention are difficult to propose. (See Cornell Exp. Sta. Bul. 219).

GOLDEN SEAL

Leaf-Blight of golden seal occurs in many plantings. It is due to a fungus
of the same genus (A/fernaria) that proves troublesome on leaves of ginseng.
Spray applications need to be worked out for it.

GOOSEBERRY

Leaf-Spot. The gooseberry leaves are attacked by the same leaf-spot fungus
recorded upon the currant (Septoria ribis Desm.), although the defoliation may
be even more severe than on the currant. In spraying experiments at this
Station, conducted by the Horticulturist, it has been found that the gooseberry
leaf-spot is more easily prevented than the currant leaf-spot. Indeed no fungus
disease upon which we have experimented is more easily prevented when the
fungicide is applied at the proper time. (See Spray Calendar). Often the leaves
from gooseberry plants have all dropped before maturity of fruit, and in hot
weather all the fruit has been lost on the unsprayed, check plants, while the
sprayed plants gave a fine yield of satisfactory fruit.

Powdery Mildew (Sphaerotheca mors-uvae (Schw.) B. & C.) is a destructive
fungus disease especially common upon English varieties, such as Industry, Crown
Bob, &c. It has been destructive also upon the Houghton. As already stated
this mildew attacks currants. From the nature of this fungus the first spraying
with Bordeaux mixture should be made early in the season. (See Bulletin 79):
Subsequent applications may be either of Bordeaux mixture or potassium sulfid.
(See Calendar). After fruit is half grown the latter fungicide is to be preferred
since it is more easily removed from the fruit.

Rust. See currant rust.
Anthracnose,

DISEASES OF CULTIVATED PLANTS 399

GOURD

Downy Mildew, &c. Gourds are susceptible to the same

fungus diseases as the cucumber. The two most conspicuous are anthracnose
and downy mildew. The anthracnose, especially, causes spotting and discolor-

ation on the gourds.

This may be arrested if, when the gourds are gathered,

they are subjected to treatment with scalding water; otherwise the development
of the tungus continues while the disfiguring increases. Field treatment in this
case is the same as recommended for like diseases of the cucumber.

GRAPE

Anthracnose. As is well known we have a
long list of fungi attacking the grape, among them
the anthracnose fungus (Sphaceloma ampelinum)
which is found upon leaves and stems as wellas
the fruit, causing definite sunken spots, usually
with a central area of lighter color. Upon the
fruit the appearance has suggested the name
‘“‘bird’s-eye-rot’’? and the last the name bitter-rot.

- Where prevalent the anthracnose may be entirely
prevented by following the directions in the use of
Bordeaux mixture as given in the calendar.

Bitter-Rot (Melanconium fuligineum (Scrib &
Viala) Cav.) of the grape is sometimes prevalent but
perhaps less frequent in Ohio than the black-rot.

Black-Rot (Guignardia
Bidwelliit Ell.) is one of
the most troublesome and

= - destructive of grape dis-
‘ig. 51. Tapes attacked by fs

anthracnose, also called Bird’sEye CASES: it chiefly attacks
Rot. the fruit and causes dark

spotting and rotting of the
green berries, but it may also attack the leaves, petioles
and cluster branches, producing circular or elongated
dead spots in them. The rotted fruits persist upon the
branches and may hang on over winter, thus carrying
the fungus from year to year. This disease, if neg-
lected, is very destructive and the longer the neglect the
greater is the difficulty in prevention. Because of the
circumstances stated, delay in beginning the treatment
increases the difficulty. It is apparently essential that
first applications of fungicide for the black rot be made
while the vines are dormant and that these be very
thorough, followed by the later applications as per
calendar. Omission of the spraying just before the
blossoms open may lead to ragged clusters, from drop-
ping of the small grapes. (See report of the U. S.
Dept. of Agr. 1896). (Ohio Exp. Sta. Bul. 130).
Crown-Gall. Crown gall of the grape is known to
give trouble in Ohio. This comes as enlargements near
the crown and on the roots. The latter occurring upon
raspberry, peach, etc. It is believed to be due to the

 

 

Fig, 52. A cluster of
grapes attacked by Black-
rot. Therotting grapes are
light brown in color im-
mediately followingdecay.

same cause as the other crown galls and to be handled only through removal
400 OHIO EXPERIMENT STATION: BULLETIN 214

Downy Mildew (Plasmopara viticola (B. & C.) Ber. & D’Ton) of the grape is
a prevalent fungus disease which has long been known and repeatedly studied.
By it the leaves are attacked and the fungus forms in them éospores by which
the winter is passed. The fungus also attacks the berries, causing brown-rot.
Gathering and burning the fallen leaves may therefore be useful. No par-

ticular difficulty attends the prevention of downy mildew if spraying is
thoroughly done.

 

Fig. 53. Leaf and stem of grape attacked by Black-rot. The lesions in the stem
are dark colored. Those in the leaf show as dying areas.

Powdery Mildew (Uncinula necator Schw.) is likewise prevalent upon both
leaves and fruit. Like all powdery mildews the parts attacked are covered over
by the web-like threads of the mildew fungus. This is successfully prevented
by the use of Bordeaux mixture as elsewhere directed. (For illustrations of
grape diseases see Report U. S. Dept. of Agriculture 1886 and 1887; also
Scribner, ‘‘Fungus Diseases of the Grape, etc.’’).

Stem Cankers. Stem cankersof the grape are rather frequent. Many of.
these are due to injury caused by freezing by which dead spots are produced
and in the process of healing these injuries become surrounded by excessive
growth and enlargements. In some instances the enlargements obtained a
diameter of two or three times the size of the stem. The preventive measures
are the same as for any freezing injury, viz., drainage and prevention of ex-
cessive late growth.
DISEASES OF CULTIVATED PLANTS 401

Dying of grape canes has been studied in one vineyard where it appears
also to be associated with crown gall and to result from other diseased conditions.
(See circular 64). In this case a portion of the vineyard died out almost com-

 

 

 

Fig. 54. Illustration showing stroma of a fungus
believed to take part in death of grape stalks. The separate
dot-growths are at times united into elongated ridges.
From Circular No. 64.

HICKORY

pletely; followed by sprouting of
a portion of the roots. In
August there was wilting and
drying up associated with dis-
eased stem conditions.

The history of this case indi-
cates that the removal and
replanting of vines will be more
successful than to endeavor to
start vines again by sprouts
from bases of injured vines.

White-Rot. Diseased con-
ditions of the earlier stages of
black-rot showing light color of
the berries leads to the use of
the term white-rot. As yet, how-
ever, the writer has never con-
clusively proved that we have a
white-rot development different
from this stage of the black-rot of
the grape in Ohio. Where grow-
ers suspect this form of rot the
method of treatment is the same
as for black-rot.

GRASSES

Anthracnoses, Smuts and
Rusts are found upon the grasses.
These are in part described
under blue-grass, orchard-
grass, red-top, timothy, and
chess.

HAZELNUT
See Filbert.
HEMLOCK

Hemlock grows freely with
us and is apparently quite free
from foliage troubles.

Heart-Rot (7rametes pini :
(Brot.) Fr.) and Sap Rot (Fomes
pinicola (Sw.) Gill) are reported
from districts where special
attention is given to the
conditions.

Leaf-Spot. <A hickory leaf-spot (Marsonia juglandis (Lib.) Sacc.) is quite
general and leads to dying of the leaves prematurely. This really merits much
closer study than has yet been given it in our state.
402 OHIO EXPERIMENT STATION: BULLETIN 214

HOLLYHOCK

Anthracnose (Colletotrichum malvarum (Braun & Casp.) Southw.) An
illustration has been published in the Journal Mycology (Vol. 6:46-48). It may
attack any part of the plant, and is a serious trouble where it occurs.

Leaf Blight (Cercospora Althaeina Sacc.) is another fungus disease of the
hollyhock. These two diseases of the hollyhock should be amenable to spraying
with standard fungicides.

Rust (Puccinia Malvacearum Mont.) On the other hand this recently
introduced disease of the hollyhock is much less likely to be prevented by
spraying. The rust fungus forms dense patches, spots or sori, on the under
side of the leaves. These are commonly about one-sixteenth inch or more in di-
ameter, of grayish-brown color and projecting below the leaf surface, while a
minute yellow spot early appears on the upper surface of the leaf. Sub-
sequently the diseased leaves drop and by the time the plants are blooming the
the stem below is bare or disfigured by the remains of the diseased leaves. At
the Station this rust has been prevalent and the complaint is general respecting
the same-trouble. It would seem wise to gather and burn all the affected
leaves and likewise the old stems as early as possible. Between anthracnose
and rust these popular old flowers are having, at present, a difficult time of it.

HORSE-CHESTNUT

Leaf-Spot of the horse-chestnut (Phyllosticta paviae Desm. ) is quite frequent.
During 1908 and 1909, tip-burn was associated with leaf-spot; as near as could
be determined, the tip-burn followed punctures of leaf hoppers or other insects
and the plants made very restricted growth during the season. It may be
necessary to take combined spraying applications for leaf-spot and the insect-
troubles. Bordeaux mixture is recommended for this purpose and has in the
past given very satisfactory results for leaf-spot. The first application should
be made when the leaves are about half grown, to be followed by others at
intervals of three weeks.

HORSERADISH

Leaf Blight (Ramularia armoraceae Fckl.) is frequent upon horseradish
and is also found upon other mustard plants. Ordinarily the severity of attack
does not call for spray treatment.

Leaf-Spot ( Cercospora armoraceae Sacc.) is less frequent and not serious in
its effects.

White Mold ( Cystopus Candidus Pers) which is so common upon shepherd’s
purse and other low plants of the mustard family, likewise attacks horseradish.
Owing to the heavy root development of horseradish the temporary parasitic
attack does not give noticeable injury.

HYDRANGEA

Leaf Blight. A leaf blight fungus (Phyllosticta flydrangeae BE. & E.) has
been observed on Hydrangea by Dr. Halsted in New Jersey. This may be
serious at times upon this ornamental plant.

Rust. Hydrangea is likewise attacked by the rust fungus. (Melampsora
Hydrangeae BC.) This may also be at times, quite serious. Remedies for
neither of these troubles have as yet been worked out.
DISEASES OF CULTIVATED PLANTS 403

IRIS

Bulb-Spot. Massey has reported a fungus causing black patches on
the surfaces of iris bulbs. This fungus (J/ystrosporum aductum Mass.) from a
description given, resembles onion smudge in its appearance and effects. Loss
is prevented by soaking the bulbs for an hour in Formalin solution.

Leaf-Blight. The leaves and roots of iris have been reported in England to
be attacked by a fungus. (Botrytis galanthina Mass.) This disease is likely
to be present in shipments of iris about the world. It is described as first
attacking the leaves and later destroying the root, thus causing the death of the
plant.

IVY

Leaf-Spot and Leaf-Blight. Leaf diseases of English ivy are occasionally
reported but have not been studied for our district. Dr. Halsted has described
a blight upon variegated forms of English ivy (Vermicularia trichella Hals. ).
In this connection we need to bear in mind that variegated plants are especially
susceptible to disease and are therefore liable to suffer.

JAPAN CREEPER
See Virginia Creeper.

LARCH

Canker and Rots. Larches are but little grown in ourterritory. In Canada
there has been described a larch canker ( Peziza willkomii Hartig.) This attacks
the trunk and branches. In common with other conifers the larch suffers from
tree infecting rot fungi. The lack of American data upon these diseases empha-
sizes our need for such studies.

LEMON

Greenhouse specimens of lemon trees are a source of a good many in-
quiries. These are chiefly leaf diseases which arise from the brown molds and
other fungi infesting these plants. As a rule they are amenable to spray
treatments with standard fungicides.

Rots. Allusion has been made to storage and transit rots of citrus fruits.
The lemon is no exception to the attacks of these rots. The blue mold
(Penicillium) is a very common form, and may be met with inalmost any of the
ordinary shipments of lemons. Brown-rot (Pythiacystis citrophthora R. E. Sm.)
is a serious trouble in California lemons especially. It appears as a white
mold on the surface of affected fruit.
’
404 OHIO EXPERIMENT STATION: BULLETIN 214

LETTUCE

Anthracnose or Leaf Perfora-
tion. This disease of lettuce was
discovered by the writer in 1896
and sent to Dr. J. B. Ellis for
description of the fungus (Mar-
sonia perforans E. & E.) It
shows upon the lettuce plants
as dying of spots in the leaves
which break free and drop out.
The fungus also produces lesions
in the midrib of the leaf. In
cases of young leaves the attacks
of the fungus causes distortion
of the leaf, especially toward the
top. Apparently very few plants
recover after being once attacked,
although one may reasonably
keep down this disease in the
seed beds and young plants by
the use of Bordeaux mixture.
For houses once seriously
infested, thorough fumigation
and soil treatment would proba-
bly be profitable. It is not gen-
erally distributed.

Downy Mildew (Bremia Lac-
tucae Regel) is the work of
another fungus which belongs to
the same class as the downy
mildew of the cucumber. It forms
yellow spots in the upper leaf

Fig. 55. Lettuce leaf attacked by Anthracnose. surface which appear below as
Ags ne oh ee by this easier tee break whitened, downy covered areas.
On the midrib the Iealone are decp-aratea. ‘The ewo ike the downy mildew of
celled spores are shown highly magniged. From Bulletin Cucumbers this one may spread
73. very rapidly under favorable

conditions, such as warmth and
surface watering in the greenhouse. Keeping water from the foliage by sub-
irrigation of the beds has been found very beneficial (Bulletin 73). Gathering
and burning the diseased leaves or plants will usually repay the labor.
Particular attention to heat and moisture will usually render spraying
unnecessary and it is certainly inadvisable except to eliminate the fungus
from the house. Avoid too high temperature or too much moisture on plants.

Rosette or Rhizoctonia. This is a very troublesome disease of greenhouse
lettuce which arises from the accumulation of the sterile fungus (Azzocfonia sp.)
in heavily manured soils used for continuous greenhouse culture. Upon the
young seedlings the Rosette fungus produces stem lesions and rotting off or
damping off of the plants (Fig. 57) or with larger plants which are later attacked
upon the branch roots or rootlets, the restricted root development prevents growth
of the plant axis and gives a basal development of normal leaves with a rosette-
shortened center of leaves. Where serious, the crop is shortened very much and

 
DISEASES OF CULTIVATED PLANTS 405

the joss of stand on smaller plants is frequently very heavy. Good results in
prevention have been obtained, both from steaming and from formalin drench
as per directions in seed and soil treatments. The fungus also attacks the
succeeding crops of tomatoes, cucumbers, etc. Attention must in all cases first
(be given to growing healthy seedling plants,to be followed by soil disinfection.
See Circular No. 57).

 

 

Ls a

 

 

 

Fig. 56. On the left is shown a healthy lettuce plant, on the right diseased lettuce plant with
Rosette effects produced by inoculation of pure culture of Rhizoctonia. The effect of the Rosette
Fungus is shown in destroying absorbent rootlets and in the growth of additional new roots; it als
prevents the proper development and elongation of the axis or stems of the plant. From Circular No. 57.
(See also Fig. 57).

Lettuce Rot or Lettuce Drop. This is by all odds the most troublesome
disease to the lettuce grower. The plants may rot off at the surface of the
earth and the central parts, especially of head lettuce, may become attacked by
the rot fungus (Sclerotinia Libertiana Wm. Fckl.) (Botrytis vulgaris Fr.). The
fungus appears as a whitened covering with a liberal production of spores in
clusters. At this Station it has not been possible to succeed with the head
lettuce because of the rot. Fumigation of house, the use of fresh or steamed
earth each year and the careful regulation of temperature and water supply,
seem to be the measures most favorable to prevention. A low night temperature,
Jess than 50 degrees F. is very desirable, while too higha temperature will
usually result in disease. Ventilation is all essential ‘during the day. Itis
desirable also to gather and burn rotted leaves and plants.

Leaf-Spot. The leaf-spot fungus (Septoria consimilis E. & M.) is frequent
upon wild lettuce plants and occassionally upon outdoor lettuce, especially in
late seasons. The small characteristic leaf-spots are not difficult to eee
from anthracnose. The remedies are confined to avoidance.

Root-Rot and Stem-Rot. A bacterial stem-blight has been described from
Vermont, but has not been found with us. A recent stem-rot infection closely
resembles rosette in the behavior and form of affected plants. Microscopic
406 OHIO EXPERIMENT STATION: BULLETIN 214 ©

examination shows that the stem tissues are somewhat brown and that the
brown and dead rootlets are occupied by the fungus which is referred to a
species of Fusarium. This disease is at present under investigation and should
be controlled, if at all, by the thorough soil treatments recommended under
lettuce rosette. It will be no use to disinfect the houses and then grow plants
in diseased soil.

 

 

 

 

Fig. 57. This shows root portions of seedling lettuce plants with dark spots, lesions caused by
attacks of the rosette fungus, AAzzoctonia, With the younger plants these attacks cause large mortality
and in very small seedlings the stem of plantlet may early collapse after the manner shown in rotting
specimens, (From Circular No. 57).

Tip-burn. Tip-burn of lettuce leaves is often brought to notice. Usually
it is associated with unsatisfactory watering in the greenhouse. or with extreme
changes to summer weather. The remedy consists in the methods of watering
employed.
DISEASES OF CULTIVATED PLANTS 407

LILY

¢

Lily diseases are frequent in all lily growing districts. With us no study
has been made, as little complaint is made to us. Doubtless the chief factor is
to secure healthy bulbs.

LOCUST

Heart-Rot (7rametes robiniophila Murr. and Fomes rimosus Berk.). In
southern Ohio the locust is reported as suffering from a heart rot trouble,
but to which of the several species occurring in different parts of the United
States, we must ascribe most injury we are not yet able to decide. Both species
occur in Ohio. The rot is described as infecting the heart of much of the trunk,
so that trunks may be of no value above the first post length or less from base.
The heart wood is converted into punk and the fungus fruits externally, as is
commonly the case.

LUPINUS

Several species of lupinus are used for ornamental or other plantings and
are liable to the same group of diseases as are found upon alfalfa, clovers and
pea.

MANGEL-WURZEL

Mangel-wurzel being a near relative of the beet is liable to be attacked by
essentially the same diseases as the garden beet. These are usually leaf-spot,
rust, dry-rot, etc.

MAPLE

Anthracnose. (Glocosporium apocrypitum E. & E.) This disease attacks
young Norway maples (See N. Y. Sta. Report ’95) and has been also identified
on the young shoots of sugar maples in Ohio. The new leaves were reported
destroyed by the fungus which is much more common in Ohio on sycamore
trees. Applications of Bordeaux mixture should check this disease.

Rhytisma and Leaf-spot. The leaves of cultivated maples are often dis-
figured by dark colored incrustations following the line of the veins. These in-
crustations are almost black and are caused by a fungus, (Rhytisma acerinum
(Pers.) Fr.) The trouble is usually not serious, but if prevalent it would seem
advisable to gather and burn all leaves attacked by it. The leaf-spot fungus
(Phyllosticta acericola (Cke. & Ell.) often causes small spots, or dead areas, in
the leaves. This may sometimes prove so serious as to call for applications of
fungicides.

Mildew. Maple leaves are overrun by the powdery mildew fungus (Uucinula)
at times, but this is not difficult to check even if spraying becomes necessary.

Tip-Burn—Sun-Scald. Tip-burn conditions upon the maple in 1908 and 1909
were similar to those described for horse chestnut and evidently due to
secondary consequences of insect punctures.

Sun-Scald or winter injury effects are frequent upon maples after the
manner of those described for apples. They are due to a killing of unripened
tissues by premature freezing and are only preventable by avoidance.
408, OHIO EXPERIMENT STATION: BULLETIN 214
MILLET

Leaf-Spot. Leaves of millet, dying from small, light-colored spots, were
recently examined. These spots are due to a fungus (Piricularia grisea (Cke)
Sacc.) and the dying may at times be enough to shorten the yield of forage.

Smut. The seeds of millet are often attacked by the millet smut fungus
(Ustilago Crameri Kornicke) which transforms them into black masses of smut
spores, much after the manner of stinking smut in wheat. This is liable to in-
jure the feeding value of the millet, although it is not likely that the smut will
injure stock when millet is fed in the usual quantities. All smutted grain, of
course, is ineffective and useless, and the smutted seed when again sown will
produce a smutted crop. The smut is prevented by the same hot water seed
treatment as that applied to prevent oat smut. In experiments conducted by
the Botanist of this Station this treatment was successful.

MULBERRY

Bacterial Diseases. Russian varieties of mulberries have new growths, es-
pecially new sprouts attacked by a bacterium. These deep dark lesions result
in cankers and all the various phenomena of the plant’s effort to heal a wound
in the wood, The trouble is so diffiult to handle that where Russian mul-
berries are badly attacked, rejections may be necessary.

Leaf-Spot. Mulberries are at times attacked by a leaf-spot (Cercospora
moricola Cke.) but this is rarely serious in our district.

MUSKMELON

Anthracnose. The common anthracnose fungus of the muskmelon (Collefo-
trichum Lagenarium Pass.) is the same as that of the cucumber. It attacks the
stems of plants of all sizes.as well as the leaves, resulting in the lesions of the
stem and dead spots in the leaves. In these the fungus produces the fruiting
podies. After the seedling stage is passed it is usually possible to keep the
anthracnose in check by the spraying as recommended for cucumbers.

The fruit anthracnose of the muskmelon (Colletotrichum oligochaetum Cav.) is
widely distributed and has occured with us. It forms yellowish, diseased spots
on the fruits and may disfigure them considerable: It is too soon with us to
estimate possible losses from it. Thorough spraying with Bordeaux mixture
should hold it in check if begun on the young fruits and repeated once or twice at
intervals.

Black-Spot. In 1908 a case of black-rot or spot-rot of maskmelon fruits was
reported with specimens. The spots were depressed and accompanied by decay.
No definite causal organism was determined, although one or more were present
in the spots. It is believed that spraying will hold it in check but the case was
referred to us to late to test this.”

Downy Mildew of muskmelon is caused by the same Plasmopara fungus as
the downy mildew of cucumbers. As we have the fungus in Ohio it does not
appear until towards the middle of August, but is then very destructive, sweep-
ing rapidly over the melon fields and leaving only devastation behind. In its
attacks the spots of the muskmelon leaves are somewhat different in shape and
usually of a darker color than in the case of the cucumber. One with
experience can readily distinguish by the use of an ordinary hand-glass. He
will then see on the under side of the leaf the violet spores and spore-bearing
DISEASES OF CULTIVATED PLANTS 409

threads of the mildew fungus. The melons which are unripened upon the vines
when attacked by mildew are practically worthless and for this reason large
losses are usually incurred. The treatment is by Bordeaux mixture, as for
cucumbers.

Muskmelon Leaf Blight is a disease more or less peculiar to the muskmelon,
although the fungus (4dlernaria sp.) which causes it has also been found upon
cucumber leaves. The leaf blight causes rather large dead areas in the leaves
which are usually distinguished j
from those of downy mildew by
their larger size and the tendency
of the central portion to break
out. The prevention of musk-
melon leaf blight is by no means
an easy matter, requiring of
itself great thoroughness and care-
fulness in the application of the
Bordeaux mixture and also re-
quiring that the downy mildew
shall be watched during the same
period. For this reason earlier
sprayings, if made before Aug-
ust 1st, should be repeated. at
fortnightly intervals, while those
after August 1st should be at
weekly or ten-day intervals.
Melon growers have succeeded Fig. 58. Muskmelon leaf attacked by leaf blight. The
by following these lines, while dead spots are caused by aspecies of Alternaria. From

Bulletin 73.
others who were less thorough
were less successful, or failed entirely. The treatment is recommended with
confidence. (Bulletins 73 and 105).

Root-Rot. (Rhizoctonia) The root diseases accompanied by rotting of the
rootlets and induced by the sterile fungus of lettuce rosette is also found on
greenhouse muskmelons. This is liable to be the case where these follow dis-
eased crops of lettuce. The prevention is the same as that for the cucumbers,
viz., thorough soil treatment.

Muskmelon Wilts are the same in general character as those described for the
cucumber. Not only the bacterial wilt disease but the wilt due to fusarium has
developed upon muskmelons in this state. The symptoms are the same as for
cucumbers, namely: sudden wilting as from lack of water, followed by dying.
The prevention treatment is the same as before recommended.

 

MUSTARDS

Black-Rot. Mustard plants of all species are liable to be attacked by black-
rot and if permitted to grow as weeds in fields devoted to cabbage growing and
will carry the black-rot trouble through the rotations in spite of the grower’s
other efforts. Let no mustard weeds survive in such rotations.

Club-Root. Mustard plants generally are attacked by the club-root fungus
(Plasmodiophora Brassicae Wor.) when this is present in the soil. For this
reason the weeds of several species may be infested upon lands that have never
been brought under cultivation. Due attention should be given to mustard plants
in new lands when designed for cabbage.
410 OHIO EXPERIMENT STATION: BULLETIN 214

  

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Figs. 59-60, Figure 59 on the left shows roots of shepherd’s purse. Figure 60 on the
right, roots of hedge mustard. Both are attacked byclub-root. Both after Halsted. Bul-
letin 98, N. J. Exp. Sta.

i
Hy

 

Downy Mildew. The downy mildew fungus of crucifers (Peronospora para-
sitica (Pers. (De By) is so universal on plants of the mustard family that it may
be usually expected. The weedy species may accordingly keep up the supply of
the parasite which attacks cabbage and cauliflower as wellas others of the
family.

Wilt. It is very zecessary that search be made as to the survival of the
fusarium of cabbage wilt on mustard weeds.

OAK

Anthracnose. The oak leaves are attacked by the same anthracnose fungus
as attacks the leaves in young shoots of sycamore and maple, but this is not so
prevalent upon oaks in Ohio as upon the sycamore.
DISEASES OF CULTIVATED PLANTS _ 41
TIMBER ROTS

Wound or Timber Rots of oaks are as yet imperfectly studied and call or
thorough investigation before many statements can be made for us.

 

 

Fig. 61. A wound parasite (Pleurotus ulmaritus) on the trunk ofa
maple tree. (After Freeman, Minnesota Plant Diseases).

OATS

Anthracnose (Colletotrichum cereale Manns.) is a new disease of oats which
attacks the roots and basal portions of the culms together with the lower
sheaths. The attack may extend even further than has yet been determined.
The spores of this fungus were found adhering to seed oats of the crop of 1907
and the outbreak of the disease was studied in 1908. It shows by the develop-
ment of the characteristic dark masses or acervule of the anthracnose fungus
upon the lower joints of the stem, portions of the root and leaf sheaths.
412 OHIO EXPERIMENT STATION: BULLETIN 214

The amount of loss resulting from it is liable to be variable since it acts by
general reduction of vigor and reduced filling of the grain head. Treatment
with formalin as for smut will certainly kill the adhering spores on seed oats,
(See bulletin 203).

Blade Blight. A disease similar to that earlier described as bacterial dis-
ease of oats (see Journal of Mycology, VI; 72) has been very serious in Ohio
during the seasons of 1907 and 1908. The phenomena are those of yellowing and
dying of older leaves associated in most cases with the presence of an abundance
of leaf sucking insects such as aphids, mites and leaf hoppers. Recent culture
and colonizing studies made at the Station show the disease to be due to two
specific bacteria working together. (Bacillus avene Manns.) (Pseudomonas
avenge Manns), These have’been isolated and described. These bacteria are
carried or transmitted by the insects or are scattered by natural agencies.
In control work in cages the organisms caused infection through the punctures of
the aphids (green flies). Evidently the control of this disease will involve
thorough seed treatment together with possible field checking of the insects dis-
tributed. (See bulletin 210).

Rust. In addition to the two species of rust found upon wheat and to be
given under that grain, there is a rust common upon oats (Puccinia coronata
Corda.), usually prevalerit during the rainy harvest weather and more or less at
alltimes. No remedy is as yet at hand.

The Scab Fungus of the oats (Fusarium
roseum Lk.) is the same species as for wheat
and attacks the panicles near filling time
It results in empty hulls with the pink fun-
gus.- The disease also survives apparently
as an internal infection of oat kernels and is
capable of destroying young seedlings after
the manner described for wheat. (See dis-
eases transmitted in the seed and also
wheat). Like that disease in wheat, it must -
be controlled, if at all, by a combination of
seed treatment for adhering spores and thor-

ough seed recleaning to exclude all light
kernels. ‘ 4

Smut. The smut of oats takes on two
forms, the loose smut ( Ustzlago Avenae Jens.)
and the hidden smut ( Ustilago Avenae laevis
(Jens.) Kell. & Swing). The first, which is
the more common, converts the entire head,
including glumes, into a sooty mass of smut
spores (Fig. 62); while in the hidden smut the
enclosing glumes remain about the smutted
grain. No other essential difference has
been found between them. Both are caused
by spores from smutted seed, or seed from
smutted grain, and both are successfully
prevented by seed treatment with hot water
or formalin as per scheme given elsew here.
(See calendar and also Bulletins 64 and 97).
An increase of yield beyond smut prevention Fig. 62, Head or panicle of oats destroyed
has usually followed seed treatment. This __ by loose smut. All the oats kernels and
alone pays for the cost of treatment and the fesmcouyneit ings Hace he ete
saving from smut loss is clear profit. masses by the loose smut fungus Us##lago.

 

 

 

 
DISEASES OF CULTIVATED PLANTS 413

OAT-GRASS

Anthracnose. The same anthracnose fungus (Colletotrichum cereale Manns.)
before described as attacking blue-grass, chess, oats, wheat, rye, etc., also
occurs upon oat-grass. It is less liable tocause serious injury here than on the
cereal grains.

Smut. There has been at the Station a smut on tall oat-grass (Arrhena-
therum elatius L.) which closely resembles loose smut of oats:‘but is, in fact, a
separate species of smut whose mycelium survives in the rootstocks of the oat-
grass (Ustilago perennans Rostrup.). The smut is thus continued in the same
plants from year to year. It is not clear whether the smut would be transmitted
in new seed, but there is some danger, at least.

ONION

Bacterial Disease. See heart-rot below.

Blight. Leaf blight or scald of onions during mid-season, when the weather
is warm and dry, is rather a common occurrence. This was especially notic-
able during 1898 and 1899. While often attributable to insects, species of fungi,
especially molds (Macrosporium Sarcinula parasiticum (B.) Thiim—. Porri
Ell.) were abundant in the seasons named. It may be possible to check these
molds by spraying. :

Fusarium Blight. This is often serious on young onions in old soil and is the
forerunner of heavy losses from soft rot in storage.

Downy Mildew (Peronospora Schlei-
deniana D’By.) is likely to occur upon
onions, although it has not been seen
in Ohio by the writer. The treatment
would be as for downy mildew of other
plants. :

Dry or Black Neck-Rot is the most
serious disease of white onions in
Ohio since the losses are so very
large from it, particularly in Hardin
County. The white onions are grown
for somewhat special markets and it
is the custom, at present, to gather
early before the tops fall over, to top
at once, and put up in crates in order.
to preserve the white color of the onion.
As arule this is not practiced with
black, red and yellow sorts, so that

 

 

 

 

 

Fig. 63, A white onion that has been destroy-

this neck or dry-rot is not so common
with them. Preliminary investigations
have been made of this trouble and it
appears to be clearly different from
the smudge fungus which also

disfigures the exterior of white onions.

ed by a blackneck or dry-rot fungus, Sclerotinum
cepivorum Berk. This parasite has entered the
onion through the green neck which was cut off
at the time of harvesting the crop, (From a
photograph by T. F. Manns).

The fungus of dry-rot or black-neck

(Sclerotium cepivorum Berk.) requires further investigation. -(See Sorauer
Pflanzenkrankheiten third edition, II 302-3). In Ohio onion districts the losses
are very serious between the gathering of the white onions and time for winter
storage while the crates are piled in buildings or in covered ricks in fields.
414 OHIO EXPERIMENT STATION: BULLETIN 214

It appears at this time that the early topping of the white onions, leaving a
green neck, offers an inviting way for the disease to enter; that the invasion is
‘in this direction appears from the sclerotia of the fungus which forms in this
region. (See illustrations). The disease appears to grow worse with continu-
ous cropping of onions and the losses have recently been so large in storage as
to render storage of white onions unprofitable. Ithas been suggested by this de-
partment that the white onions should be gathered and ricked in crates at once,
either in buildings or covered with tent or temporary enclosure of building paper
and disinfected or treated with formaldehyde gas as per the spray calendar.
(See formula elsewhere). The enclosure shoud not be opened for 24 to 48 hours
after treatment. In this manner it is hoped to keep down the infection of the
white onions as well as of any others from similar troubles.

Heart-Rot. (Bacterial). This disease has been under investigation and
appears to come in all varieties of onions, following the topping, by its rapid
invasion of the center of the bulb through bacterial infection. It should be con-
trolled by attention to disinfection of the topping machine or to similar treat-

ment to that recom-
mended for dry-rot.
This disease ends in
the complete destruc-
tion of the bulbs
through a soft rot dif-
erent from that de-
scribed under soft-
rot.

Smudge. This fun-
gus (Vermicularia
circinans Berk.) de-
velops as asuperficial
spotting upon the ex-
terior, especially at-
tacking the white
varieties; it is really
an anthracnose of
onions. For some
time, because of its
coincident develop-
ment with the black

Fig. 64. Onion spotted by the smudge fungus. This fungus be- neck or dry-rot, these
comes very bad in land where successive crops of onions are grown, two troubles have
The fungus is also a factor in causing dry-rot of onions and set onions. been confused. It

is now apparently
clear that there is no connection between the two, although this fungus causes
dry rotting of sets and bulbs. The smudge fungus is cumulatively worse
on old land where onions are grown consecutively. Apparently also in addition
to rotation of crops the formalin drip treatment described under smut gives
good results in keeping down this fungus. In field experiments made hereto-
fore, the onions have been lost in storage from the dry-rot and the smudge
disease has not been studied very fully in storage; apart from this it is believed
to have little or no connection with the commoner storage rots, although the dis-
figuring effects of badly spotted onions reduce their market value, and rotting
does take place as a result of it. The illustrations give characteristic appear-
ances of these compared with healthy onions.

 

 

 
DISEASES OF CULTIVATED PLANTS 415

Onion Smut, on the other hand, is prevalent to a considerable extent in Ohio.
and is one of the most destructive of the smut fungi known to pathologists.
This onion smut (Urocystis Cepulae Frost) unlike the other smuts with which we
have to do, propagates itself almost indefinitely in the soil when this once becomes
infested. Whenever a new crop of onions is grown from seed in this infested soil
the smut attacks the young seedling onions, in whole or in part, and a very con-
siderable loss results therefrom. If, however, onions sets are putin such soil,
or seedling onions that have been started under glass in healthy soil are trans-
planted to smut infected
soil, the smut fungus
cannot attackthem. The
explanation seems to be
that the smut threads.
areonly able to penetrate
the leaves of the young,
tender seedlings. This
onion smut is now known
tooccur in fields at Berea
Perry, Madison and
near Chillicothe. Atthe
latter place it has seri-
ously embarrassed some
of the growers of onions
for sets; for this work
transplanting is, of
course, out of the ques-
tion. In Connecticut Ex-
periment Station Report
for 1889, it is stated that
flowers of sulfur have
been used to sow with
the seed in infested
svil, and this remedy
has given but slightly
inferior results to any
other yet tried at this
Station. Forty percent
formaihyde, known com-
mercially also as forma-
lin, has given better re- Fig. 65. Sound and smutted onions, gathered in midsummer
sults than sulfur in 1900. The healthy onions were grown on badly diseased soil by the use o¢

At Berea, Chillicothe Formalin Drip treatment.—From a photograph by T. F. Manns.

and latterly at Madison,

experiments have been conducted to determine a practicable field method for
smut prevention. The best method has proved to be that of formaldehyde drip
with seeder. (See bulletin 131). The formaldehyde solution is made at the
rate of one pound of 40% formaldehyde to 25 to 33 gallons of water. This is
applied with drip attachment on seed drill at rate ore eae per acre for
field onions. The same results can be obtained i “dpe? furrows by applying
solution with sprinkler after seeds are scattered until well moistened. This
formalin treatment insures the disinfection of a layer of ‘soil near the seed and:
permits the germination and the early growth, of the seedling onion, past infec-
tion stage, before the smut fungus can again occupy this soil. Thegains from this
treatment, both in the onion set work and in field onions are very large, amount-

 

 

 

 

 

 
416 OHIO EXPERIMENT STATION: BULLETIN 214

ing to 100% to 200% increase. This method has recently been applied success-
fully in the Connecticut Valley by a representative of the United States Devart-
ment of Agriculture.

Soft-Rot and Storage Rots. The Assistant Botanist has recently studied a soft-
rot (Fusarium sp.) of onions which shows in field, but more seriously in subse-
quent storage. This soft-rot is produced by the fungus Fusarium, yet under study.
It not only causes anearly blight but also invades the onion bulbs quite rapidly
after storage infection. The problems of control are essentially those of
storage rots including dry-rot.

In onion storage it seems to the writer probable that disinfection of the
onions after placing in storage buildings either by sections or otherwise: using
the formaldehyde gas treatment will give excellent and safe results. This
needs yet to be worked out. :

ORANGE

In greenhouses oranges are frequently grown and complaints come to us as
to the troubles upon them. The chief of these troubles is a black mold (Capmod-
tum citri Berk. & Desm.) on the foliage and at times upon the fruit. Spraying
with fungicides has usually brought satisfactory results and develops no
special injury to orange foliage.

Fruit Rots. Orange rots in stored fruits are often brought to our attention,
but do not properly belong to our state work. They are the result of mold
attacks following bruising. The blue mold fungus (Penicillium glaucum Link.)
and the green mold fungus (Penicillium digitatum (Fr.) Sacc) are both common.
These are described in other publications. (See Bul. 8, Bureau of Vegetable
Pathology, United States Department of Agriculture, also Bul. 184; Calif.
Exp. Sta.).

ORCHARD-GRASS

Anthracnose. Orchard-grass is attacked by the same anthracnose (Colleto-
trichum cereale Manns.) as attacks wheat, rye, oats, blue-grass and timothy.
The development is shown in a similar way by the black masses of the fungus
upon the basal portions of the culms and sheaths. Ca

PALM

Leaf Diseases. Frequent complaint is made of palm leaf diseases in conser-
vatories; the department has been able to study these but little and finds more
often that they are the result of over-watering. Several diseases have been re-
ported on palm leaves. Among these we have an anthracnose fungus (Gloeos-
forium Allescheri Bres.) of Kentia. Dr. Trelease has reported upon another
fungus on Phoenix (Zxosporium palmivorum Sacc.). This also attacks the
leaves causing ultimate death. Another leaf disease is described from Europe
upon Chamaerops (Graphiola Phoenicis (Mong.) Poit.). It is caused by a fungus
which is not infrequent on the date palm. Sprays such as Bordeaux or Lysol are
recommended for these palm leaf diesases,

PEA

Anthracnose. The anthracnose or pod-spot of the pea (Ascochyta Pisi Lib.)
often develops into a serious blight of field peas grown for canneries. This was
studied by the department and it was found that the anthracnose fungus infects
the seed peas so that these when planted give diseased seedlings and the
consequent loss of crop. (See Bul. 173). The illustrations will show how the
fungus spots the pods and thus has an opportunity to enter the developing
DISEASES OF CULTIVATED PLANTS. 417

seed peas. It was shown by spraying ex-
periments with Bordeaux mixture mixture
that healthy seed peas may be grown.
The growth of healthy peas for seeding
disposes of the problem of anthracnose.

Leaf-Spot. Other leaf-spots besides
those of the anthracnose are sometimes
found upon the pea and are apparently
caused by another fungus (Sepforia Pist
West.) These, if giving trouble, will be
controlled by the spraying for anthracnose.

Powdery Mildew (Zrysiphe communis
Walir.) The mildew fungus often attacks
the pea and at times entirely destroys its
fruitfulness, It may be known by the
whitish coating produced upon the leaves
and by the dark, pin-head spots of the
fungus observed to be situated in these
white coverings. The same fungus like-
wise attacks the bean. For either plant

spraying with Bordeaux mixture, as per

directions in calendar, will be found
beneficial. The first applications should
be made promptly.

Wilt. A wilt of pea, apparently allied
to that of cow pea ond other forage crops
of the south has been referred to a species
of fungus Neocosmospora (Fusarium). As
yet it has not been especially studied in
Ohio.

 

 

 

 

 

 

Fig. 66. Pods of French June field pea
spotted by anthracnose. After Van Hook,
Bulletin 173.

 

 

Fig. 67. Leaves of pea
showing spots caused by
anthracnose fungus-slight-
ly magnified. After Van

_ Hook. Bulletin 173.
418 OHIO EXPERIMENT STATION: BULLETIN 214

PEACH

Anthracnose. An anthracnose fungus (Gloeosporium laeticolor Berk.) has
been described upon the fruit of peach and has been found in Ohio, though
rarely. Careful spray treatment as for scab should be successful against this
disease. :

Crown Gall. This is
a very contagious

 

a =

disease of the peach
and ‘of other plants,
notably daisy, rasp-

berry, and blackberry,
due to a_ bacterium
(Bacterium tumefaciens)
Sometimes it produces
excrescences -and en-
largements upon _ the
root and branches of the
affected plant. More
commonly the galls are
found upon the stems
just below the surface
of the earth. These vary
in size and in location,
even occurring upon the
small roots, and less
frequently upon the stem
at some distance above
the ground. In some
recent experiments (Bul-
letin 104) it was found
that the gall trouble
became communicated
from diseased  rasp-
berries to peach trees
set in the plantation.
In some instances the
loss from crown gall

 

 

 

 

Fig, 68. Root of nursery peach tree attacked by crown gall.

has been large and there is, in my judgement, no other
disease common to several of our fruit trees that is so
threatening in its ravages. The peach trees attacked in
most cases perish without producing fruit. This applies
when the trees are affected at nursery age—the usual
condition. Purchasers cannot afford to set such dis-
eased trees nor nurserymen to ship them. As yet the
only treatment that we can recommend is to dig out and
burn the diseased trees, and to avoid planting affected
stock. Indeed no affected stock should be received.
This, with other diseases, has been treated in Bulletins
92 and 104.

Frosty Mildew. Occassionally the frosty mildew fun-

  

Fig. 69. Crown gall attack.
ing stem of peach tree.

gus (Cercosporella persica Sacc.) occurs, whitening over
the under surface of the leaves. As yet it has not been
a serious disease.
DISEASES OF CULTIVATED PLANTS. 419

Gum-Flow. The gum-flow diseases of the peach are frequent but have, as
yet, been imperfectly studied in our state. Wehave no distinct gummosis, al-
though in some varieties of peaches it would seem this is a weakness or a form
of injury due to climate followed by gum exudations. Bark borer injuries pro-
duce a well-marked gum-flow.

June Drop is often named by peach growers as a specific trouble. It consists
in the dropping of the young peaches during the month of June, though drop-
ping sometimes comes.earlier. The cause seems to be physiological and need
not be feared where the trees have been prevented from overbearing, or protected
from the effects of drought by thorough cultivation the previous season.

Little Peach is a disease much discussed.in Michigan and is quite serious
in the fact that the peaches on diseased trees never come to proper maturity or
develop marketable character. Dr. Smith has found that the root hairs on many
such trees are not healthy and thus it appears that some specific trouble is
located there.

Leaf-Curl (Exoascus deformans B). The leaf-curl fungus is at times one of
the serious pests of the peach grower. However, destructive leaf-curl does not
occur every year. The curl fungus survives as mycelium in the buds from year
to year. It is therefore present each season, though possibly in varying amount.

 

 

 

 

 

Fig. 70. Leaves of peach attacked by leaf-curl. The attack of the fungus causes rapid cell mul-
tiplication and results in the distorted shapes. From a photograph.
420 OHIO EXPERIMENT STATION: BULLETIN 214

 

 

 

Fig. 71. Eleven-year-old Elberta peach tree, unsprayed, defoliated by leaf-curl, Nofruit, From
Bulletin 148,
DISEASES OF CULTIVATED PLANTS 421

 

Fig. 72. Eleven-year-old Elberta peach tree, sprayed, March and April, 1903, with soda-lime-sul-
fur-vitriol, under direction of the owner. Foliage and fruit crop saved by the treatment. From Bul-
letin 148,
422 OHIO EXPERIMENT STATION: BULLETIN 214

We have found in Ohio that serious leaf-curl comes when cool weather, with
frequent rains, prevails during April, May and June. It is to the April weather
that the most serious trouble seems attributable. With low temperatures and
frequent rains during the early half of this month we may safely predict an
outbreak of leaf-curl (Bulletin 92). During such weather the fungus develops
rapidly and the new leaves are affected as they are protruded from the bud._ In
a modified sense the same takes place during May and in a still more limited
sense during June. Successful prevention of leaf-curl is secured by thorough
early treatment with Bordeax mixture. Indeed, it appears that a spraying at
any time shortly before the blossoms open is several times more effective than
any application afterwards. It appears that more effective results are secured
by spraying two weeks before blossoming than immediately before the blossoms
open. In any event an application made just before the blossoms open is more
effective than at any later date’ Jime-sulfur applications for scale insects are
effective to prevent leaf-curl. Whale-oil soap has also proved effective applied
at this time, though not safe at much earlier dates. It is more expensive than
Bordeaux mixture. (See Bulletins 104 and 148).

Leaf-Spot of the peach may be due to a variety of causes and in no cases
studied have they proved destructive. One fungus (Cercosperella persica Sacc.)
is often mentioned. These leaf-spot are illustrated and very briefly discussed in
Bulletin 92. a ,

Pustular Spot of the peach is a disease referable to a minute fungus (Helmin-
thosporium carpophilum Lev.) which is apparently spread by spores that alight
upon the upper surface of the fruit, flourish there and produce minute, light-
brown spots, often surrounded by an angry red border. The red border is con-
spicuous in earlier varieties and is sometimes elevated and pustular in appear-
ance. This fungus greatly disfigures the fruit and is very easily prevented.
Three applications of Bordeaux mixture have reduced the amount of pustular
spot to less than one percent; whereas unsprayed trees gave more than sixteen
percent of spotted fruit, much of which was seriously damaged. (Bulletin 92).

Powdery Mildew (Sphaerotheca pannosa (Wallr.) Lev.) sometimes attacks
peach in our state, but rarely with serious results. The attacked leaves some-
times turn white and are sometimes distorted. Spraying with potassium sulfid
or self-boiled lime-sulfur would be successful. :

Rot or Brown-Rot. The brown-rot fungus (Sclerotinia (Monilia) fructigena
(Pers.) Schroet) isamong the most destructive of the fungi on the peach, yielding p lace
only at times to leaf-curl. Unlike leaf-
curl the brown-rot prevails during
warm, showery weather, and withsucha
weather period is likely to occur at any
time ofthe year. In April, ifthemummy
peaches are permitted to remain on the
trees from the preceding year, the fungus
may affect the twigs through the blos-
soms and thuscauseserioustwig blight.
Itisa matter of common remark that the
branches upon which rotted peaches are
found often perish from the effects of the
rotfungus. The survival ofthe fungus in
these ‘‘mummy”’ fruits and the produc-
tion of ascospores from them are well
proven. No one variety seems more sus-

 

ceptibletorotthan others, althoughsome ee Rotted a mn dried or mummy peaches
sorts are more liable to ripen during Will peed Sees oe Perel These maeuales

rainy weather and then rot worse. The ‘howe —
DISEASES OF CULTIVATED PLANTS. 423

control of rot demands: First, careful removal and destruction of all mummy
rotted peaches in which the fungus survives; Second, thorough spraying of
the trees before blossoming, as for leaf-curl; Third, subsequent spray treatmert
with self-boiled lime-sulfur as per calendar, may be profitable under certain
conditions.

Root-Rot. In some instances, notably at Gypsum, Ohio, where peach trees
were planted in a dense, clay soil, the roots often decay, apparently from the
attacks of some fungus. Trees thus attacked usually perish soon. Whether
the trouble is primarily due to the fungus or to the location in which the trees
are grown has not been determined.

 

 

sea os

  

 

 

Fig. 74. Peaches of the Salway variety with one side blackened and cracked from scab. This loss
is prevented by proper spraying.—From Bulletin 148. .

 

 

Another root-rot has been further studied and found to be prevalent where
orchards are set in newly cleared land, if following growths of oaks. The
attack upon the roots show the rhizomorphs of the root-rot fungus as in apple
root-rot which has later been more often noted in the west.

Rust. <A rust fungus occurs upon the peach but not to a serious extent
in Ohio. :

Scab or Black-Spot. This fungus (Cladosporium carpophilum Thum.) is a
serious drawback in the growth of certain varieties which seem susceptible.
These are Morris, White, Salway and some other late sorts. It causes dark
spots upon the- fruit followed by cracking and entrance of the rot fungus with
serious results. To control this disease, spraying results reported in bulletins
104 and 148 obtained by the use of dilute Bordeaux mixture were very satisfactory,
but secured with some injury to peach foliage. In 1908-9 studies were made in
an orchard near Brownhelm where self-boiled lime-sulfur was tested in compar-
ison with dilute Bordeaux mixture. The results are very promising and indicate
that self-boiled lime-sulfur is the remedy to be applied at intervals of two to
three weeks after foliage appears.

Stem Blight. A stem blight of the peach was studied several years ago by
the writer. (See bulletin 92). Itis due to a specific fungus which in this.
instance attacked the stems of nursery stock causing a constriction, and this is
424 OHIO EXPERIMENT STATION: BULLETIN 214

in line with the effects of the fungus described from Europe as a constriction
or lacing disease. While in the case studied there was loss of nursery stock,
due possibly to some injury to which it was exposed, there has been little recent
troub‘e. Infection may surely be prevented by treatment with fungicides.

 

Fig. 75, Stems of nursery peach trees attacked by Constriction fungus.
(Phoma persicae Sacc.). The trouble causes dying out of the diseased parts of
the stems which are shrunken whereattacked. The detail structure of spores
and pycnidia are shown magnified about 500 diameters.—From Bulletin 92.

Winter Injury. In our climate the severe freezing of winter often injures the
trunk and branches of peach trees. The common killing back of new growth
by freezing is afamiliar phenomenon. The common killing of the trunk on one
side, usually the west or southwest, is alsoknown. Many instances have been
studied. Wherever there has been late growth of the trees, followed by severe
winter cold, such injury may be expected. Late cultivation is therefore to be
avoided. Winter injury to fruit trees may be attributed to the drying out of
the trees and it is worth while to consider whether by mulching, or soil condi-
tions, the tree may not be made to have an abundant supply of available
moisture, when the upper soil is frozen hard. Much injury to peach trees from
treezing uccurred during February, 1899, and in the fall and winter of 1906-7.
In the larger portion of these earlier cases there was more water in the soil, or
aoout the trees, than in the less injured localities. More exposed situations also
gave more injured trees. In 1906-7 the freezing was sudden upon unripened
wood. (See Bulletin 192.)
DISEASES OF CULTIVATED PLANTS. 325

 

Fig. 76. Peach tree, two years old, Carpenter, Ohio—one of those remaining alive though injured
by freezing of 1906-7. Dead branches and ridge on trunk mark dead portion. From Bulletin 192.

Yellows. Peach yellows is a serious, contagious disease of this fruit in most
portions of Ohio. Only in certain seasons may we find yellowish color as a
marked symptom of affected trees. The true symptoms of yellows are: 1. Pre-
mature ripening of the fruit which is highly colored, often purplish spotted, and
has the flesh marbled with red. 2. The premature growth of winter buds,
resulting in excessive branching on new shoots, and the development of slender,
wiry branched twigs. 3. Resting buds or adventitions buds are formed on the
trunk and branches; these grow into sickly shoots with pale, narrowed leaves,
and usually become much branched, with tips like veritable brooms. Aside
from these specific evidences of yellows which serve to distinguish yellow color
from true yellows disease, there are others less easily déscribed but none the
less useful to the practical observer. This disease may be recognized late in the
426 OHIO EXPERIMENT STATION: BULLETIN 214

season by the late, adventitious growth. The sources of disease are diseased
trees or affected nursery stock, more often the former. The remedy is to remove
and to burn the yellows trees, root and branch, on the spot where found. Drag-
ging diseased branches may spread yellows and all such trees are a menace.
To leave an open hole over winter and replant the next year is a safe practice.
(See Bulletins 72 and 92 for fuller discussion).

 

Fig. 77. Peach Yellows, winter buds of diseased tree unfolding
in autumn. (After Smith, Farmers’ Bul. 17, U. S. Dept. Agric.)

Recent investigations of this disease show that it is due to an enzyme which
converts the leaf chloryphyll into a diseased form, causing yellows conditions.
It is doubtless this enzyme which is transmitted, as in the case of tobacco, by
actual contact. These discoveries have changed in no way our method of hand-
ling the disease. (See enzymatic diseases in introduction).

Rosette of peach is a disease of the southern states which appears to be
similar in cause and transmission to peach yellows.
DISEASES OF CULTIVATED PLANTS 42>

PEAR

Anthracnose. An anthracnose fungus (Colletotrichum sp.) occurs upon the
fruit of the pear in the east, but has not been seen in Ohio.

Black-Rot (Sphaeropsis malorum Pk.) of the pear is the name applied to the
rot like that of the quince and apple and due to the same organism. While it is
less frequent as a source of fruit rot upon the pear, it is present both in this
form and in the form of branch attacks or cankers.

Pear Blight or Fire Blight is one of the most serious drawbacks to pear
growing. The symptoms of dead twigs and branches are well known, In sub-
stance our knowledge of pear blight is about this:—It is due to a bacterium
(Bacillus amylovorus (Burr.) which, in the old cases of blight, winters over in
the blighted parts. With April and May showers there is some exudation of
watery substance from these parts, containing the zoogloa masses of the bac-
terium; when visited by insects these are by them transmitted to the opening
blossoms. The microbe there breeds in the nectar of the blpssom and in that
manner attacks the branches; once within the tissues the microbe may spread
indefinitely. Some varieties of pears are more susceptible, apparently, than
others, which simply means that in them the. microbes spread more rapidly.
There is not a single variety of blight-free pear in our region. The remedy con-
sists in cutting off and burning the blighted parts
each autumn, extending the work to the crab-apple,
apple and indeed to every variety of pome fruit which
is attacked by this bacterium. In recent years Mr.
Wm. Miller, of Ottawa County, has reported better
results in blight control since he practices thorough
spraying of the trees in early spring with lime-sulfur.
(Bulletin 79. Year-book U. S. Dept. of Agric. 1895).

Crown Gall. The crown gall attacks the pear both
at the crown and upon tips of roots. It is less rapid
in its destructive effects here than upon the peach,
though but slightly less serious. Enlargements may
be readily detected and they are usually of denser,
woody growth than upon the peach. The same rem- Fig 78. Crown Gall on end
edies apply here as with that fruit. of pear root.

Leaf Blight of the pear is produced by the leaf
blight fungus (Zxztomosporium maculatum Lev.) which causes spotting and dying
of the leaves, also cracking of fruit. ‘The diseased leaves show a dense, dark
colored coating on the under side. This disease is readily and successfully
prevented by the use of Bordeaux mixture as a spray.

Leaf-Spot of pear is another fungus disease which may flourish despite the
use of Bordeaux mixture, as generally applied. This fungus (Septoria piricola
Sacc.) appears not to yield to the standard fungicides. It produces small, cir-
cular dead spots in the leaves; the spots in later summer may drop out, leaving
holes. It is quite prevalent, but as yet -no specific recommendations can be
made for it.

Pear Scab is a fungus disease allied to Apple Scab; the pear. scab fungus
(Fusicladium pirinum (Lib.)Fuckl.) being very similar in development to that of
apple scab. This fungus was very abundaut in 1898. It may cause spotting of
the leaves or spotting of the fruit of the pear but is not readily distinguished
from the other troubles save by the use of the microscope. It is prevented by
the use of Bordeaux mixture. :

 
Card OHIO EXPERIMENT STATION: BULLETIN 214

Rust. The development of the early form of the cedar rust sometimes occurs
upo.: pear as upon apple.
Sun-Scald is the name applied at times to the trunk injuries upon pear which
are more commonly but the work of the pear blight bacterium at such points.
Sooty Disease. A sooty disease of pear fruit like that which occurs upon
apple (see pages 372-3) likewise occurs upon the fruit and is also controlled by
similar treatment.
: PELARGONIUM

Dropsy. Some varieties of cultivated pelargonium, possibly called begonia,
suffer seriously from dropsy. One bright scarlet flowered variety in particular
has been cultivated at the Station. It often suffers from dead spots in the leaves.
Before these spots in the leaves die, examination will show that there are wet
looking places upon the under side of the leaf which appear translucent when
held between the observer and the light. These are nothing more than leafcells
which have become so gorged with water as to be ruptured. The break down
extends to adjoining parts and then tends to produce the spots before described.
This is purely a physiological trouble due to excess of water. The remedy is
clear. Withhold water until absolutely necessary.

PEONY

Stem-Rot—Wilt. Frequent complaint comes to us of the dying of the stems of
peony. The writer has had similar trouble. The disease has not been fully
investigated. Massee and others have identified a rot fungus( Botrytis (Sclerotinia)
paconiae Oud.) to which more or less of the stem rot may possibily be
referred. The symptoms are a gradual dying of the leaves. Examination
shows stems to be rotted near the ground or often very much higher. A strong,
insoluble fungicide might be successfully sprayed upon the stems without cover-
ing the leaves.

PEPPERS

Anthracnose. Two anthracnoses of peppers have been described from New
Jersey, as occurring upon the leaves of the plants (Gloeosporium piperatum
(E. & E.) (Colletotrichum nigrum (Ells. & Hals.) although the latter may at
times be found upon fruits. In addition to these Dr. Halsted has demonstrated
that cultures of the apple bitter-rot as well as the bean anthracnose, will flourish
upon fruits of pepper.

PERSIMMON

Leaf Diseases. So far as known to the writer no strictly fruit diseases of the
persimmon occur in our district. Wemay have at least three leaf diseases.
These are an anthracnose fungus (Glocosporium diospyri (E. & E.), the true
leaf-spot fungus (Cercospora atra (E. & E.) and a powdery mildew (Podosphaera
oxyacanthae (D. C.) De By.). The mildew will show like others, as a whitish
covering upon the leaves, while the others are likely to inflict real injury to the
leaf tissues. All should be possibly controlled by spraying.

PHLOX
Leaf-Spot. Cultivated phlox is frequently attacked by a leaf-spot fungus
(Septoria divaricatae E. & E.). This mars the appearance of the leaves but is

not often serious.

Powdery Mildew. There is a powdery mildew fungus also (Zrysiphe Cichor-
acearum D. C.) sometimes found upon cultivated phlox. It develops as a whitish
covering over the leaves and other parts. Both should yield to spraying

properly done.
DISEASES OF CULTIVATED PLANTS 429

PINE

Damping-Off. A damping-off fungus (Fusarium sp.) has recently been very
troublesome with seedlings of white pine in theeast. This has been investigated
and remedies have been tried successfully. These are either dilute sulfuric acid
or powdered copper sulfate and lime; the former being sprayed on the seedlings
about the base and the latter applied as dust. (See Cir. 4, Bur. Plant Indus.).
It is likely that with efforts to grow white pine for timber purposes in this state,
troubles of this type will not be restricted to this parasite.

Leaf Blight and Leaf-Spot. Leaf troubles have been met in most areas where
white pine grows naturally or is being cultivated very largely. One of these
so-called leaf blights is referred to a fungus, (Septoria parasitica Hartig).
It has been found in adjoining states if not in Ohio. Another leaf-spot fungus
(Phoma strobi Berk and Br.) is quite prevalent upon white pine in Europe. It is
believed that this parasite or a closely related one, (Phoma strobilinum P. C.)
occurs within our borders. Remedies have yet to be worked out for these troubles.

Root-Rots are to be expected in addition to the damping-off fungus before
mentioned, especially among seedling pines under culture.

Rust. In Europethe blister rustfungus (Cronartium ribicolum Dietr. Peri-
dermium strobi Kleb.) has been long known as a serious drawback to the culture
of the white pine. Curiously enough this rust has until recently not been known
inthe United States. Not long since warning was sent out by the Department of
Agriculture that this rust had appeared in America and should be sought for
upon its alternate hosts, the white pine (Aecidia) and the currant and gooseberry.
(Uredo- and Teleutospores). Upon the pine the aecidial stage develops numerous
orange cluster cups infecting the stem toward the base. This causes high mor-
tality among the young pines. Upon the currant and gooseberry the uredospores
show yellow color which darkens as the teleutospores form. These are to be
sought in August or early September, and by reason of the importance of this
rust merit early attention by students of these diseases.

PLUM °

Black-Knot. This is the same disease as that described under black-knot of
cherry. It is more frequent upon the Damson than upon the other European
plums, but requires only the removal and burning of the knots each year before
March, in order to grow plums successfully and without serious injury from this
disease.

Brown-Rot is by all odds the most
serious disease with which Ohio plum
growers have to deal, outranking by
far black-knot, shot-hole fungus and all
the other ills plums are heir to. It is
the same in character as the rot of other
stone fruits. As with the peach, the
rot fungus (Sclorotinia (Monilia) fruc-
tigena (Pers.) lives over winter in the
mummy rotted plums of the year before
and possibly, to a limited extent, in
affected branches. The first step in
successful control of rot is the removal
and burning of these old plums. The
next step is to spray thoroughly, before

Fig. 79. Cluster of plums destroyed by rot the buds open, and to continue the
causing “‘mummies. Mummy” plums are ; eaten
dangerous whether left upon the tree or dropped spraying and picking the rotted plums

to the ground, since they carry the rot fungus 4s circumstances demand. Likewise,
over the winter period.

 
430 OHIO EXPERIMENT STATION: BULLETIN 214

controlthecurculio. For details of treatment see calendar. No halfway meage
ures will yield satisfactory results in dealing with plum rot.

Cankers. In Europe trunks of the plum as well as trunks of forest trees
suffer from canker caused by adistinct species of fungus. As yet we have no
true proof of cankers dueto these parasites in Ohio. The parasiteis Nectsia
ditissima.

Crown Gall. This diseasehas been reported upon the plum as upon the
peach, but is less frequent. :

Leaf-curl. On Japanese varieties of plum,
the leaves at times suffer from leaf-curl at-
tacks similar to those upon peach. It should be

, Teached by the same remedy, winter sprays.

Mildew. The powdery mildew fungus of
the cherry (Podosphaera oxyacanthae(D.C.)
De By) also occurs at times upon the plum,
but is usually rather easy to control.

Pockets or Bladders. American varieties
of plum are sometimes attacked by a fungus
‘(Exoascus sp.) related to the leaf-curl fungus.
This causes enlargement of the young fruits
which are hollow; because of this condition
they are sometimes alluded toas ‘‘bladders.”’
The conditions which bring about the disease
are the same as those of leaf-curl, viz, ex-

- cessive cool wet weather in the early season.
The winter spray as for leaf-curl should be
effective.

Fig. 80. Plum leaf attacked by Shot- Root-Rot. Plums are susceptible to at-
hole Fongis. “This fungusds the same as tack of root-rot as in the case of other orchard
that causing Leaf-Spot on cherry, but in °
this case the diseased areas of the leaftend fruits where set following timber or fruit
to drop out, leaving ‘‘shot-holes."” trees that have suffered.

Shot-Hole Fungus is at times a very de-
structive disease of the plum. It is duetothe same fungus (Cylindrosporium
fadi Karst.) which attacks the cherry, although in this case even more serious
injury is liable to result than with cherry trees. Where trees are defoliated by
shot-hole fungus the fruit is of small value and the trees put forth new foliage
and blossoms, thus leaving immature wood and a sappy condition for trouble in
winter. Under such circumstances the secondary losses may beenormous. This
fungus is readily prevented by spraying with standard Bordeaux mixture, the
first application being made when the leaves are half grown, and two more at
intervals of about three weeks.

Winter Injury or so-called Sun-Scald. In 1896-7, following neglected cases of
shot-hole fungus which defoliated the trees in the fall of 796, some plum orchards
were almost totally destroyed by the severe winter freezing. The sappy trees
were not in condition to withstand the severe cold, 15 degrees. Young trees
were killed to the snow line while older trees had the sides of the trunk, com-
monly that facing to the southwest, severely injured. Plum trees were again
injured, by freezing in 1906-7. (See Bulletin 192), The prevention of this trouble
lies in the prevention of the shot-hole fungus and the avoidance of the conditions
named. In soire cases it is possible that protection of the trunk by straw or
boards might be profitable.

Rust upon the plum has been collected in some of the western states, but at
present has not been seen in Ohio by the writer.

 
DISEASES OF CULTIVATED PLANTS 434

POPLAR

Anthracnose. Species of poplar or cottonwood are at times attacked by
anthracnose ({Marsonia populi Hals.). It produces similar effects to those of an-
thracnose upon sycamore.

Rust. The leaves of poplars are frequently attacked by the rust (Welampsora
populina (Jacq.) Lev.) which disfigures the leaves by the spots caused through its
development. The thrifty growth of poplars usually overcomes these foliage
diseases under favorable conditions.

POTATO

Bacterial Blight. This is a serious disease of the potato; it also’attacks the
tomato, tobacco and egg-plant. It has been referred to a microbe (Bacterium
solanacearum Smith). The parts of the stem attacked die off suddenly and the
tubers from the affected plants have a dark discoloration of the tissues in a
distinct ring at a slight distance from the exterior of the potato. Fungicides
are practically useless for this disease. Such diseased tubers should not be
planted nor should potatoes follow a diseased crop of tomatoes, egg-plants or
potatoes. (Div. Veg. Path. B. No. 12, U. S. Dept. of Agric.)

Black-Leg. In much of Europe and in America the bases of potato stems are
often attacked in the early season by a basal stem-rot which causes serious
check to the growth of the plants. The diseased parts show well-marked lesions
due to the work of a bacterium (Bacillus phytophthorus Appel.). Dr. Smith has

recently investigated the disease in this country and has found it widely dis-
tributed. In Ohio it occurs to a certain extent and is at times quite similar in
its effects to those referred to rosette. Measures of control will largely consist
in rotation of the potato crop. See Bulletin Maine Expt. Station 174 (1909).

 

Fig. 81. A potato destroyed by Dry-Rot. This shows the characteristic appearance
of the rotted potato.—From a photograph by T. F. Manns,
432 OHIO EXPERIMENT STATION: BULLETIN 214

Dry-Rot. The dry-rot fungus (Fusarium oxysporum (Schl.) has become gen-
erally prevalent in Ohio. This attacks the plant as the result of seed tuber or
soil infection, causing wilt troubles of the plants (see Fusarium Blight) as well as
dry-rotting of the tubers in storage. This tuber dry-rot is shown by the mold-
like development of the fungus on the tubers. All such tubers should be rejected
and rotation in potato growing should be practiced. Partly infected lots of
potatoes held in storage should be promptly used. The infection of seed tubersis .
‘shown by cross sections near the stem end of the tuber at digging time or later.
Where infection occurs there will be browning of the vessels near the exterior of
the potato. In limited infection only small spots will show, but as the infection
advances these brown tissues show as characteristic rings approaching that in
bacterial blight. These spotted tissues yield the fusarium of infection in cultures
as has recently been shown by the assistant botanist. Since we know that this
parasite develops as a blight of the plant proper, we need to reject all diseased
tubers for seed. (See Fusarium Blight).

Early Blight of potatois a premature spotting
and dying of the potato leaves, due to the work
of a parasitic fungus (Alternaria solani (E. &
M.) Jones & Grant). The occurrence of the
early blight, however, is liable to be influenced
by the general vigor and other conditions of the
plant; yet there is no just basis for denying, in
the light of our present knowledge, the parasitic
nature of this disease. Jones has madecultures
of the fungus and produced the disease by inoc-
ulation (Vt. Exp. Sta. Buls. 24 and. 28; Rept.
1892) and has secured most admirable results
by the use offungicides. This successful spray-
ing initself is in the nature of proof of parasitic
character. In the potato work at this Station
it has been the uniform practice to spray
thoroughly with Bordeaux mixture, adding ar-
senites for the insects, as required, and it has been
many years since we have suffered any serious
loss from early blight. However, the spraying
for early blight will not prevent the bacterial
disease above described, and it is doubtless the

Fig.82. Farly Blight on potato confusionof these two diseases that has led tosuch

leaf. (After Jones). differences of opinion among potato growers as

to the efticiency of spraying with Bordeaux

mixture for early blight. There is real danger of the confusion of early blight

with the Fusarium blight described in the following paragrph. Our recom-

mendation is still that contained in the spray calender, namely: to spray with
Bordeaux mixture or some modified form of it.

Fusarium Blight. Early in the season of 1909 it was discovered that a small
area of one of the unfertilized potato plots at the Station was dying out. . Sub-
sequently the area became larger and investigation showed the fungus to be that
of dry-rot, which see. Later it developed that the yield of the entire tier of plots
grown in three crop rotation, died prematurely although spraying had been
practiced as usual. The dying plants showed infection and the dead areas had

 
‘ DISEASES OF CULTIVATED PLANTS 433

in them black masses of a species of fungus (Vermicularia) whose relation to the
disease is undetermined. At digging time it was found that in addition to grub
injury, the tubers were very generally infected with the markings of the dry-rot
fangus in the conducting tissues. Sections of the stem end showed brownish
discolorations of the vessels, and occasionally tubers showed marked invasion
by the fungus. Tubers collected elsewhere sometimes showed these discolorations
of the vessels extending half the length of the tuber. Injury by grubs favored
infection. ‘
Following these discoveries quite thorough studies were made of potato con-
ditions in the state, and it developed that the fusarium blight prevailed in local
fields throughout the entire potato growing area. While some growers had ob-
tained fine crops in spite of limited infection other growers had suffered seriously.

 

 

 

 

 

 

 

 

 

Fig. 83. Potato tubers attacked by Dry-Rot Fusarium, showing sections near the stem-end of
healthy (No. 1) infected potato tubers. (Nos. 2-4) This infection may be easily discovered by cross sec-
tions made with a sharp knife, and sections from sterilized tubers give cultures in Petri dishes. At
times the discolorations extend to the middle of the tuber. )From a photograph by T. F. Manns).
One grower in Summit county, who had succeeded very well in 1908 had such
serious loss of crop from fusarium blight that he was led to attribute it to spray
injury since blighting and dying went on in spite of the spray treatment. Inves-
gation showed that his entire area was very badly infected with this fusarium.
He was advised of the fact and warned against using infected seed or immediate
planting of infected land. It developed also that northern grown seed showed
up. quite satisfactorily. On further examination it developed that the seed from
Red River Valley and from parts of New York and possibly parts of Michigan
was nearly free from infection by this fungus. It was also developed that seed po-
tatoes stored in cellars have sometimes given much less satisfactory return than
seed from the same field stored in outdoor pits. This would seem to be explained
by the known fact that (Fusarium oxysporum) the dry-rot fungus, makes slow
progress at low temperatures, that is 42° or below. This disease presents a real
problem in potato growing for the year of 1910, and interpreting the results of
1908 in light of the experiences of 1909, one is led to infer that the disease then
prevailed and accounted in part for the general early dying of potato tops..
434 OHIO EXPERIMENT STATION: BULLETIN 214

In Europe, especially in Germany, in 1907 and possibly in the seasons since
much complaint has been made of a similar disease to that described by
Stewart as a leaf-roll disease (Blattrollkrankheit). In the European disease as
well as in the stem blight of potatoes described by Stewart in New York (See
Bulls. 101 and 138) and in our present fusarium blight, the leaves of the affected
plants lose color and roll upward from the border. With this occurs a general
loss of green in the plants. Orton, who has made a general study of the disease
throughout the country, regards the fusarium of dry-rot as the causal organism,
and finds very serious checks upon potaio growing have resulted in San Joaquin
county, California, upon so-called tule ‘lands where continuous cropping in
potatoes has been more or less practiced. The evidence is conclusive that we
have in the dry-rot organism a blight organism of the potato plant which is at
the same time a soil infesting as well as a seed tuber infecting fungus. In
addition to this, incomplete observations support the idea that some spread of the
organism takes place as with other fungus parasites in the field. In the matter of
preventive measures and remedies, the first consideration should be given to seed
tubers. These should be of such source and character as are clear from infection.
‘This infection may easily be determined by cutting across the stem end of the
tubers. Evidently cellar stored seed is dangerous during this period of epidemic.
In the matter of spray prevention we have evidence in a cooperative test in Portage
County, that the spray holds back the advance of the development. Upon dupli-
cate plots where strong Bordeaux mixture was used, the gain was at the rate of
13 bushels per acre above any other sprayed plots; and 9 bushels per acre above
the checks. These plots remained green longer than any of the others and show
a decided reaction to the copper fungicide. From the behavior of certain hills
in the various fields whose tops remained green in spite of the general infection,
breeding for blight resistance should give decisive results.

Late Blight or Rot of the Potato (Phytophthora infestans De By) called in Europe
‘the potato disease’’ is caused by a downy mildew fungus. This mildew spots
the leaves, producing a downy, felt-like covering in spots on the under side of
the leaves of infested plants. This causes prompt dying with wet-rot conditions
of the leaves and the tubers are rapidly destroyed with wet-rot appearances. The
potato Phytophthora is a disease which like its host plant is accustomed to
somewhat cooler conditions of climate than usually prevail in Ohio. However,
in the years 1904 to 1907 all the summer months were several degrees below the
normal; this resulted in continuous out-breaks of the blight or rot, culminating
in 1906-7. In 1908 under warmer or drier conditions while the fungus was found
at Wooster it did not inflict damage here or elsewhere in the state. It is unlikely
to be injurious in Ohio, except in seasons cooler and more moist than normal.
(See table of seasons page 354).

Spraying for late blight is entirely successful and should begin by the 20th of
July, being repeated at intervals of two weeks and applications made at the rate
of 100 gallons per acre on full grown vines. The duration of the spraying will
depend upon the maturity of the plants, in the late crops reaching four or occas-
ionally five sprayings.

Rosette. The Rosette or Rhizoctonia disease often prevails in Ohio, especially
where potatoes are grown on acid soils. This acid condition is evidently
favorable to the fungus which attacks the stems of the young plants or even in
early developments of the stems, these are often rotted off below the surface for the
earth. In later developments the elongation of the plant axis is stopped and a
rosette appearance is shown in the leaves. The disease survives by the red-
DISEASES OF CULTIVATED PLANTS 435

 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
   

Fig. 84. Showing a plant of pota-
toaffected with Rosette. The elonga-
ted injury below the soil surface
shows as dark-colored in the figure.—
From Bulletin 139.

Tip-burn. Potato leaves
often show dead margins or
tips even where no parasitic
attack can be _ discovered.
Such ‘‘tip-burn’’ effects may
also be increased by any extra
weather stress as of drouth
or by spray injury. These
conditions are to be met by
avoiding the causes which
bring them about. .

Wart-Disease. This di-
sease, also called ‘‘canker’’
and ‘‘black-scab’”’ is caused

brown sclerotia upon the seed tubers;
these are largely controlled by seed
treatment with formaldehyde or cor-
rosive sublimate. (See bulletins 139
and 145).

Potato Scab is a well known para-
sitic disease of the potato tuber that
needs no extended description. Whether
due to fungi or bacteria, or both, the
practical prevention of potato scab con-
sists in destroying the parasites on the
seed potatoes and then in planting
them in soil free from those organisms.
The organisms in question will usually
be found in soil on which potatoes were
grown the previous year, or in that
freshly manured. The materials used
by this Station in treating for scab are
two, namely, solution of corrosive sub-
limate and solution of formalin, as per
strengths given in spray calendar. It
is ineffective to treat the seed and
then plant on scab-infested land. See
also Wart-disease.

Fig. 85. Sases of potato stems showing lesions caused by
Rosette Fungus. The shaded areas were dark with an
abundance of the fungus, and the tops showed conspicuous
Rosette effects. From Bulletin 139.

by a soil infesting fungus, (Chrysophlyctis endobiotica Schilb) and has recently
’ become established in New Foundland and possibly at other points in North
436 OHIO EXPERIMENT STATION: BULLETIN 214

America. It was discovered upon potatoes from upper Hungary in 1896 and
has since become distributed over much of northern Europe including Germany,
England, Ireland, Scotland and Wales. Apparently this wart disease is the
most serious potato trouble yet met with in cultivation, since it causes large
warts upon potatoes but partially infected and converts those badly attacked
into corky masses not unlike lumps of coke. Such tubers are entirely unfit for
human food though they may be used for stock food after cooking. The fungus
causing the disease survives in the potato by resting spores as well as by its
vegetative parts and appears to remain as a soil infestation for five to six years.
Seed treatment is not effective in controlling the disease. Every effort should be
made to secure the exclusion of the disease from the United States and to’
recognize it should imported tubers carry the trouble. See Giissow, Bulletin 63
Central Experimental Farms (Ottawa) and Orton, Circular 52, Bureau Plant

Industry 1910.
PRIMULA

Rot. <A rot of Chinese primula due to Botrytis and similar to that on peony
has been reported and may be expected with us.

PRIVET
Anthracnose. Privet in hedges is frequently attacked by anthracnose
(Gloeosporium cingulatum Atk.). This shows itself by lesions in the younger
stems and results in dying of the portions of the attacked branches beyond the
lesions. This weakens the hedge and sometimes results in‘ secondary conse-
quences. While spraying has not been fully worked out for this disease, it
should prove an effective remedy at the proper time.

PUMPKIN
Downy Mildew and Wilt attack pumpkins after the manner described under
muskmelon and cucumber. The remedies are the same as there stated.

QUINCE

Anthracnose. The fruits and possibly the branches of quince are attacked
by an anthracnose fungus(Glomerella rufomaculans Sp. & V. Schr.)which is the
same as that causing bitter-rot in apple. According to our knowledge of the
survival of this fungus, attention must be given to gathering and burning of
“mummy’’ fruits and to the cankers produced, if any, upon the branches. The
spraying treatment necessary is the same as that for apple bitter-rot.

Black-Rot. The fruit and foliage of the quince are attacked by black-rot.
The black-rot multiplies very rapidly in the fruit of quince and often causes loss
of much of that produced. This fungus (Sphaeropsis malorum Pk.) also develops
as a leaf-spot upon the foliage causing defoliation. It is liable to attack the
branches after the manner determined for apple. Tohold this fungus in check
very careful spraying is required at times, but as a rule it is easier to keep down
the black-rot on fruit and foliage of quince than to keep it down on susceptible
apples. The spray used is Bordeaux mixture.

Leaf-Spot of another kind which is identical with that upon pear is found at
times formed upon the quince. It is controlled by the same treatment as the
black-rot.

Blight. The blight upon quince (Bacillus amylovorus (Burr.) De Toni.). is
slightly less destructive than that upon pear. It is caused by the sane bacterium
and requires the same watchful care and attention as in the case of pear.

Pale-Rot. This (Phoma cydoniae Sacc.) is reported from some of our states
and may occur fn Ohio. There is no evidence to indicate that it will require
more prolonged treatment than black-rot or leaf-spot.
DISEASES OF CULTIVATED PLANTS 437

Rust (Gymnosporangium sp.) also occurs upon the quince when trees are
near cedars which carry the cedar apples and distribute spores. Labor must
be devoted to the destruction of the source of infection as in the apple.

RADISH

Blacx-Rot, Club-Root. Black-rot (Bacterium campestre (Pamm) and club-
root (Plasmodiophora brassicae Wor.) occur upon the radish at times and are of
the same nature and cause as these diseases upon other mustards, especially
cabbage and caulifiower. The attention to control will be similar to that for
cabbage.

Downy Mildew and White Mold (Peronospora parasitica De Bys and Cystopus
candidus Pers.) also occur upon the leaves of radish, the latter more especially
upon younger plants. These are the same diseases that have been described
upon other mustard growths.

RAPE

Black-Rot, Club-Root, etc. Rape, as other mustards, is attacked by a group
of diseases which are common upon plants of the mustard family. These are
black-rot, club root, white mold, etc., that are more fully described under
cabbage, cauliflower and radish.

RASPBERRY

Anthracnose (Colletotrichum venetum (Speg.) Hals.). The anthracnose
ungus is a frequent bane to the raspberry grower. It attacks the young canes
and so spots and injures them, as well as the foliage, that when the time arrives
for ripening the fruit the plants are unable to do this and the crop is largely
lost. The Horticulturist of this Station has always succeeded in holding this
disease in check by use of the methods of spraying recommended in the cal-
endar for anthracnose. Care, however,
must be used in the application of the
spray to reach the stems of the young
canes and to keep the fungicide from

 

do injury. :

Cane Blight. Serious dying of
raspberry canes has occured in some
of the northern districts where they are
largely grown. These troubles range
from ‘‘dieback’’ to impaired vigor in
which there are seeming brown patches
upon the stems. As a rule these have
failed to yield a specific organism and
may be the result of root conditions
which appear to be quite unsatisfactory
on both raspberry and bla&kberry, as
described under the former.

Crown Gall is at present one of the
most destructive diseases attacking
raspberries. In some well marked
cases upon the variety known as

= Thompson’s Prolific (Bulletin 79) eel-
Fig. 86. Raspberry stem attacked by An-

thracnose. This causes “‘birds-eye” spots of the WOrms have been suggested as the
stems. After Scribner. possible cause of the gall production;

 

 

 

 

the leaves of bearing canes whereit will ||.
438 OHIO EXPERIMENT STATION: BULLETIN 214

but whatever the cause of the galls attacking that variety
we have found them transmitted to the peach in the same
soil and we have found that practically all of the varieties
of raspberries are attacked by a similar trouble producing
like excrescences. These galls result in the destruction of
the bearing canes, and where the raspberries are planted
in orchards the disease, it would seem, may extend to the
orchard trees as well. Late investigations show that a
bacterium isthe cause of crown gallonthe almond. (Science
N. S. Vol. XXIII, No. 575, pp. 424, 425; by Erwin F. Smith,
U. S. Dept. of Agric.). Prompt removal and burning of all
affected canes is the only method of treatment. Indeed it
has been demonstrated from the very beginning that a
healthy raspberry plantation cannot be secured by the
selection of apparently healthy plants from diseased areas.
Nothing remains but to secure plants from healthy
plantations. ,

Bacterial Blight of raspberries has been described by this
Station; it has not recently proved serious. (Bulletin 78).

Leaf-Spot and Rust. The leaf-spot fungus, already de-
scribed’for blackberries and dewberries, upon which it is Fig. 87. Crown.
more commonly found, was prevalent in 1899 upon rasp- Gall on raspberry
berries. The only remedy for rust (Cacoma. nitens Schw.) plants. These also oc-
is the removal and destruction of all clumps either wholly CU 08 the roots.
or partially infected. The leaf-spot fungus (Septoria rubi West.) will
yield to spraying with Bordeaux mixture. Winter injury usually occurs
and is shown by the killing back of canes which fail to mature properly. The
remedy must lie in the avoidance of the conditions. \

 

RED-TOP

Anthracnose (Colletotrichum cereale Manns.) was found upon red-top, as also
upon timothy, orchard-grass, wheat, rye, oats and chess. The symptoms are
the same as for the other grains; the disease attacks the culms and sheaths upon
the lower part of the stem. The chief interest which comes from the disease
upon grasses is the means this may serve to carry the disease of one rotation
to the next in cereals.

ROSE

Anthracnose. An anthracnose fungus (Glocosporium rosae (Hals.) attacks
the rose, causing defoliation of the canes; indeed the whole plant is attacked.
This behaves very similarly to the anthracnose fungus of the raspberry. Young
plants are found most susceptible to the disease. The methods of handling are
practically the same as far the anthracnose of the raspberry.

Crown Gall. Crown gall trouble essentially the same in character as that of
raspberry, occurs on roses but requires no separate description here.

Leaf Blotch (Actinonema Rosae (Lib.) Fr.) often causes dark spotting
of the leaves. The frost-like, branching growth over the leaf-surface is often
very pretty in design though injurious in effect. If the rosehouse is too moist,
or if other conditions be slightly unfavorable, the fungus seems to flourish.all
the better. It may be checked by the use of Bordeaux mixture or by dilute
copper sulfate solution, as recommended for cucumbers in the greenhouse
(One pound to fifty gallons).
DISEASES OF CULTIVATED PLANTS 439

Rose Mildew is attributed to the fungus (Zrysiphe
pannosa Lev.) whichis commonly prevalent in rosehouses;
it is also found occasionally out of doors. This mildew
is, for the forcing house, largely diagnostic, indicating,
when prevalent, uneven temperatures. Proper attention
to the matter of heat is the best preventive. Sulfur is
often sprinkled upon plants and is frequently used upon
the steam pipes, but it is not clear that the influence is
very great.

Nematodes. Among the most serious of the rose
diseases is that caused by the eelworms or nematodes
which attack the roots. As with cucumbers, these
parasitic worms induce the growth of small bead-like
galls upon the roots of the rose. The leaves dry up
from the margins,
the plants generally
turning yellow and
breaking down as
the outcome of this
interference with the
proper work of the
roots. This subject

Fig. 88. Branch of rose of nematodes is dis-
root with Nematode Galls. cussed at length in
Bulletin 73. No suc-

cessful remedy has been found for plants once
attacked. The method of prevention con-
sists, as inthe case of cucumbers already
cited, in the proper steaming and treatment
of the soil designed for use in the rose
benches.

Rust (Phragmidium subcorticium
Schrank.). This is occassionally met and
proves very disfiguring. As yet we can ad-
vise nothing more than the choice of rust
resistant sorts.

 

 

RUTABAGA

Rutabaga is attacked by the same
diseases as attack turnips.

RYE

Rye Anthracnose. This new disease was
very serious upon rye in 1908 and was surely
prevalent in 1907. The spores are carried
by adhering to the seed grain and can be
discovered in centrifuge separations of grain Fig. 89, Head and upper portion of
washings. In rye fields the anthracnose stem or rye attacked by anthracnose,
attacks both the ‘heads and the lower ‘The point of attack upon the head is
portions of the culms. The localized attack eae eg a
upon the head (rachis) kills all that portion the dark spots are the acervuli of the
of the spike above the point of attack and the anthracnose. From Bulletin 203.
grain is but partly deqeloped. See Fig. 90.
Upon the bases of the stems, including the roots, the fungus develops its dark
masses often closely packed together and dotting both stem and sheaths (see
figure). In 1908 the loss of yields in rye were from 25 to 60 percent of the total crop.

 

 

 

 
440 OHIO EXPERIMENT STATION: BULLETIN 214

For control of the disease thorough separation of all the light rye kernels in
the seed. and subsequent seed treatment are recommended. (See Bulletin 203).

4
&

 

Surge ret ay
\
GQ) <=

 

Fig. 90. On the left kernels of rye shriveled from an attack of -
anthracnose; on the right, normal, healthy kernels of rye. From Bulletin
203.

Ergot occurs occasionally in rye; the fungus ( Claviceps purpurea (Fr.) Tul.)
attacks the kernel and transforms it into a large club-shaped dark mass, the
ergot of the druggist. The amount of ergot is usually not enough to be aserious
trouble in our state. Ergotism in domestic animals is sometimes caused when
' diseased rye is fed to them. :

Rust. The species of rust which occur upon wheat are also found upon rye,
(See wheat).

Scab. The scab (Fusarium roseum Lk.) as is shown by recent work at this
Station attacks rye almost as freely as wheat. The fungus in question is shown
by recent work to be the same as that in wheat. The remedy is the same as that
recommended for anthracnose.

Smut. The fungus ( Urocysts occulta Wallr.) of stem and blade smut in rye
occurred at this Station in 1909. It attacks the culms, leaves and leaf-sheaths
but not commonly the floral parts. The smutted parts swell and burst open in
elongated lines. Seed treatment may reduce this smut but hardly prevent it
altogether.

SALSIFY

White Rust (Albugo tragopogonis Tul.) attacks this plant and is sometimes
destructive. The best results seem to be promised by avoiding sources of infec-
tion and by spray treatment.

SORGHUM

' Bacterial Blight of sorghum is somewhat similar in its general appearance
to the bacterial blight of corn already described, and is caused by a specific
organism (Bacillus sorghi Burr.). It has been described in the Kansas Experi-
ment Station Report for 1888.

Grain Smut (Cyntractia Sorghi-vulgaris (Tul.) Clinton) attacks the seed of
the sorghum plant. The hot water treatment may be adapted to prevent this.

Head Smut (Sphacelotheca reiliana (Kuhn) Clint.) occurs occasionally where
sorghum is grown, but is less common than grain smut.

SOYBEAN

Wilt occurs in most districts where soybeans are grown. We have had very
few reports in Ohio.. Indications show that the one most likely to occur is that
due to a wilt fungus (Fusarium).
DISEASES OF CULTIVATED PLANTS 441

SPINACH

Anthracnose occurs upon spinach but is not definitely known in our district.

Downy Mildew. The downy mildew fungus ( Peranospora effusa (Lev.) Rabh.)
is already known upon lamb’s quarters and may appear upon the cultivated
spinach of the same order. It shows as discolored or dead spots in the leaves with
felted, downy covering underneath. Methods of prevention here would be as
for cucumbers, except that applications could scarcely be made after the plants
are nearly developed.

In older trucking districts other diseases such as white smut and scab have
been reported, but are not known to occur with us in Ohio.

SNAP-DRAGON

Anthracnose. Stewart has described an anthracnose fungus of:snap dragon
(Colletotrichum antirrhini Stew.). This attacks the leaves causing brown spots
and is at times serious. It may be successfully combatted by spraying with
Bordeaux mixture. ae aie,

Stem-Rot. A stem-rot (Phoma sp.) also attacks the stems of snap-dragon at
any point above the ground. It is especially severe on thé younger or sucker
stems.

SQUASH

The squash is attacked by diseases already described under cucumber,
namely, anthracnose, downy mildew and the wilts. The remedies are likewise
the same.

SOLOMON'’S SEAL

Leaf Diseases. Solomon’s Seal is attacked by afungus (Aecidium conval.
lariae Schul.) which causes characteristic orange-colored cluster cups, and by
a leaf-spot fungus (Phyllosticta cruenta (Kickx.). This latter disease is liable
to give increasing trouble in culture. :

Smut. Parts of this plant are also attacked by a smut fungus (Urocystis
colchict (Schl.) Rabh.). I believe this is rather infrequent.

SPRUCE

Leaf-Spot. Norway spruce in Ohio has suffered seriously in 1908-9 from
attacks by a leaf-spot fungus (Phoma sp.). This fungus causes the discolora-
tion of the leaves (needles) also their dropping. The fruit bodies of the fungus
occur upon the scales of the branches as well as upon the leaves and are evi-
dently capable of surviving from year to year. This leaf-spot or leaf blight has
been reported from several counties upon hedge plantings, upon large shade
trees and upon sizes grown for Christmas trees. Drouth conditions in 1907 were
a large factor in this matter causing the death of many spruce trees in 1907 and
1908. It is believed that winter and early summer sprayings will have some
effect in checking the leaf trouble. This experience shows the need for mulches
about Norway spruce, especially in the southern portion of Ohio.

Seedling diseases are liable to prove troublesome thus chécking efforts to
grow seedlings of spruce.

STRAWBERRY

Aborted Fruits. In certain seasons, and especially in 1908, there were.many
reports of misshapen and aborted fruits. In certain cases the salable fruit: was
less than 50 percent of the whole. These misshapen fruits are rarely the result
of disease, more often they are the indirect result of imperfect pollination. The
effects. of weather conditions in hindering pollination and making it imperfect are
well known. Some bright sunny weather is all essential.
442 _ . OHIO EXPERIMENT STATION: BULLETIN 214

Anthracnose ( Glocosporium /ragariae Mont.) has been found upon strawberry
leaves in other states; it has geen less trouble than the other foliage diseases

with us pap to this time.

 

 

 

 

 

Fig. 91. Leaves of strawberry attacked by Leaf-Spot.
The lighter centers have dark borders. This fungus forms
ascospores in the strawberry leaves. From a photograph by
T. F. Manns. :

old leaves and the fungi upon them, as well as
right principles and is commonly successful.

SUGAR BEET

_ Crown-Rot (Phoma betae
Frank) has been discovered
in most of the sugar beet grow-
ing states and is liable to be
present in Ohio in the factory
district.

Leaf-Spot. The sugar beet,
which is beginning to be
extensively cultivated with us,
has been injured by the leaf-
spot fungus (Cercospora beti-
cola Sacc.) and by other
diseases. The leaf-spot pro-
duces small, dead areas in
the beet leaves, followed at
times by dying ot all the
leaves. For this fungus Bor-
deaux mixture may be applied
with confidence, at intervals
of three weeks. The first
application should be made
when the plants are about 5
or 6 inches high.

Root-Rot occurs at times,
particularly upon beet seed-
lings where planted in rich
trucking soil. The fungus a a

 

Leaf-Spot or Rust so-called
is the most serious disease of
older strawberry leaves. The
leaf-spot fungus (Sphaerella
JSragaria (Tul.) Sacc.) matures
in the old leaves. In the
earlier spots on young leaves
three forms of fungi are found,
most of which are probably

‘stages in the development of
the leaf-spot fungus. This
disease is essentially one of
the season before the crop is
injured. Spraying upon new
plantations after picking any
fruit present will usually be
found profitable. The practice
of burning over strawberry
beds after picking to destroy

possible insects, is based upon

 

Fig. 92. Leaf-Spot trouble on sugar beet.
DISEASES OF CULTIVATED PLANTS 443

appears to be the same as that attacking the greenhouse seedlings of lettuce
tomatoes, 'etc., (hizoctonia sp.) and‘can apparently be reached only by similar
methods.

Beet Scab affects the roots of the beet as the scab does potato tubers. It is
thought to be due to the same organisms. It may be avoided largely by avoid-
ing the conditions for scab already mentioned under ‘potato scab. Rotation of
sugar beets will probably be required to escape this and other diseases.

SWEET POTATO

Bin or Soft-Rot is encountered by the sweet potato growers. The fungus
(Rhizopus nigricans Ehrh.) producing it may be present in the plant bed and
apparent as dark spots or rotted tips on the plants at setting. All such plants
ought to be discarded if avoidance of disease is sought. Some experiments
were made at Marietta in 1897, to prevent or reduce this rot, but without posi-
tive advantage in the keeping qualities. A dope or mixture Of 6 parts earth to
one part flowers of sulfur was dropped in handfuls and the plants set through
the mixture thus bringing it about the roots of the plants very nicely. Smoother
potatoes were obtained and these separated more readily from adherent earth,
but no better keeping qualities resulted for that year. The potatoes were har-
vested, however, during a wet period and conditions were less favorable than is
often the case.

Soil-Rot (Acrocystis Batatas Ell. & Hals.) isa serious disease of sweet
potatoes for which the above described treatment has proved successful in New
Jersey. (N. J. Exp. Sta. B. 126).

Stem-Rot (ectria Ipomoeae Hals.) attacking the stems and roots has
appeared in Ohio sweet potato fields, apparently introduced by affected seed.
Such seed should be avoided. Rotation may also be necessary.

White Mold or White Rot (Cystopus [pomoca-panduranae (Schw.) Farl.) is
rommon upon the Man-of-the-earth and the wild morning glory (Convolvulus
hederaceae) in the sweet potato districts, but apparently is not frequent upon
sweet potato foliage.

Black-Rot. This disease of sweet potato roots shows in dark, somewhat
sreenish spots of varying diameter. It causes serious losses in the roots and
rom diseased potatoes gives ‘‘black shank’’ in great abundance upon the young
plants. The fungus (Ceratocystis fimbriata Ell. & Hals.) has been described as
a result of Dr. Hailsted’s work in New Jersey. In treatment the measures are
largely preventive in the choice of healthy seed, healthy sprouts and the sterili-
zation of the plant beds.

SWEET CORN

Bacterial Disease has at times proved serious in sweet corn fields, but is
apparently the same in character as that attacking sorghum, broom corn and
field corn.

Smut (Ustilago Zeae Beckm.) also attacks sweet corn and where crops are
grown consecutively in garden, the amount is sometimes excessive. The cause of
it is the same as that of field corn and the conditions of control are the same.

SYCAMORE

Anthracnose (Gloeosporium nerviseguum (Fckl.) Sacc.) is periodically very
destructive on the foliage of the sycamore, extending at times to the younger
shoots. The warm wet springs appear to be favorable to it; such was notice-
ably the case in 1908 and again in 1909. The outbreak in these years extended
all over eastern United States. While the disease should be amenable to fungi-
cides, it has been neglected.
444 OHIO EXPERIMENT STATION: BULLETIN 214

' Powdery Mildew. The leaves of the oriental sycamore, which is planted

' largely in Cleveland and other cities, are much disfigured by the powdery
mildew fungus (Microsphaera alni(?), This was studied by the writer in Cleve-
‘land in 1909. It was found that younger trees were subject to attack by the
mildew fungus late in the season, so that a foot or more of thetip of the shoot
was disfigured by the mildew and many of the leaves were prevented from full
development. The fungus does not complete its development early, and up to
November 15th no spore sacs were formed. This leaves moderate doubt as to the
exact identity of the fungus. It is hoped to hold this mildew in check by spray-

ing which seems to be necessary on younger trees of the oriental sycamore.

sg

: TIMOTHY

; ‘Anthracnose (Colletotrichum cereale Manns)occurs upon timothy and as al-
ready noted on blue-grass, orchard-grass, red-top; wheat, rye, etc. The attacks
‘so, far studied, are confined to the culms and sheaths upon the lower part of the
stems showing small dark masses of the anthracnose fungus as spots upon them.
This shows that the timothy is liable to carry over the disease between the wheat
crops.
; pactenal Blight of Head. See blue-grass.

Rust (Puccinia poculiformis (Jacq.) W) Some seasons this is very preva-
lent upon timothy resulting in much spotting and premature drying up of the
foliage. This was true to a notable degree in Ohio in 1908.

Smut (7illetia striiformis (Westd.) Wint.) attacks the blades of timothy and

' produces interesting developments in them. As a rule the amount of smut is not
_.serious... (See smut of blue-grass).
TOBACCO

Bacterial Blight. The same bacterium that attacks potato, egg-plant, etc.,
“at times attacks tobacco plants, especially in the early development. (See wilt).
'" Bed-Rot. Tobacco plants are often de-
_ Stroyed by damping-off fungi; at times even the
- root-rot fungus may be present in the beds.
Owing to the need to use beds several years in
succession for plant growing the same fungus
which gives us trouble in greenhouses is very
liable to give us trouble here. In the old world
some of the common damping-off fungi are re-
ported. With us our particular bed-rot troubles
are due to Rhizoctonia. For checking this dis-
ease it seems desirable to treat the tobacco beds
in. late fall with formalin drench at the rate of
21-2 to 3 pounds of formalin to 50 gallons of
water; this to be applied to beds at the rate of
one gallon per square foot after spading up
thoroughly and incorporattng all fresh manure
before the treatment is applied. The beds .
should also be fairly moist. After this treat- Fig. 93, Tobacco plants showing
bed-rot, Rhizoctonia.
ment no stable manure should be applied,

although mineral fertilizers can be used. Ifthe treatments are delayed till spring
it will be impossible to sow sooner than two weeks following this drench. (See

Circular 59, 1906). “

 

 
DISEASES OF CULTIVATED PLANTS, 445

Broom-Rape. In certain infested districts in Brown county the common
broom-rape (Orobanche Ludoviciana Nutt. } attacks the roots of tobacco, while ey
in Kentucky the hemp broom-rape (QO. ramosa) also occurs even to a greater 4
extent than in Ohio. Nothing can be done to prevent these attacks of this para-
site which produces its own. flowers and seeds after once established. If losses

are large it would be wise to rotate crops on infested land to get rid of the
broom-rape.

 

 

 

  

 

Fig. 94. Roots of white burley tobacco plant attacked by broom-rape. Each of these masses
attached to the root shows beginning of the plant which will grow up in larger dense form, and produce
an abundance of blossoms and seeds but no leaves. Each one of these must have started froma
buried seed of the broom-rape, Orobanche Ludoviciana Nutt.

Curing House Troubles. At times tobacco growers have in very moist weather
troubles from rotting in the curing house. . These are called shed-burn, pole-
burn, etc., and are difficult to control under unfavorable weather conditions.
Thorough ventilation of the houses is certainly-necessary where these are feared.

Downy and Powdery Mildew (Peronospora sordidaB. & B.) and (Erysiphe
communis Walir.) both occur in the old world, but up to this time have not been
listed in America.

Leaf-Spot (Cercospora nicotianae E. & E.) (Phyllosticta nicotiona E. & E.)
occurs in some tobacco states, but is very rare with us.

Mosaic Disease also among the enzymatic diseases, is not very common upon
tobacco, except in seasons when the normal development of the plants is inter-
fered with by excessive rains and water logged soils. In Connecticut the disease ©
is known as ‘“‘calico,’’ diseased plants showing a mottled appearance due to
the alternating areas of dark green and yellowish green in them; they are
446 OHIO EXPERIMENT

veritable mosiacs. As shown a few years since by Beijerinck, Wood and others,
these diseases and others of their class show a yellowing of foliage due to oxi-
dizing enzymes in the leaves. Further as shown in experiments made in 1904,
(see Bulletin 156) at Germantown, this disease is communicated from one plant
to another by touching. The experiment included touching a succession of
plants after touching a diseased plant; these touchings were sometimes repeated.
During the period of one month there was an increase of 67 percent in those
touched following contact with diseased plants. This shows the advantage of
handling mosaic plants at separate times from healthy ones.

 

Fig. 95. Roots of seedling tobacco plants from soil inoculated
with Thielavia basicola: A. Soil sterilized with formalin (1 to 200
and B. untreated. After Gilbert Bulletin 158, Bur. Plant Ind., U.
S.D.A.

Root-Rot. Root-rot (7hielavia basicola Zopf.) on tobacco was first discov-
ered by the writer upon plants received from Clermont county in 1899; since this
time it has been more or less serious during wet seasons. In the vicinity of
DISEASES OF CULTIVATED PLANTS 447

‘Hartford, Conn., notably at Litchfield, this
disease has been troublesome on certain soils;
the same fungus has been found upon ‘catalpa
seedlings in Ohio. It is better known as attack-
ing the roots of violets. In all cases there isa
blackening and rotting of the roots of seedling
plants where they are attacked. Thorough
steaming of the bed soil should be practiced
where this trouble comes in, to avoid transplant-
ing it tothe field. In the field as has recently
been pointed out ‘by Gilbert and Briggs, the
check on growth of tobacco is much. greater in
wet seasons than in dry ones. Apparently
attention must be given to the drainage of the
land which becomes infected if this is to be
continued in tobacco.

Wilt (Bacterium solanacearum Erw. Smith)
has occurred frequently in North Carolina and
has more recently been sent to the writer from
shade plantations in Florida where considerable

Fig. 96. The fungus of tobaccoroot- acreage was lost in1908, due to infection through
rot (Thielavia basicola Zopt.). Camera the soil. This bacterial disease has recently
lucidia drawing or the fungus as it heen investigated by Stevens and others, but it
a aes Foie ae is not believed any methods of treatment will
svores. All magnified 565 diameters. evade the necessity for rotation. (See Bulletin
From a drawing by J: M. VanHook. 156 also potato wilt.)

White Speck has been studied in North
Carolina and attributed toa specific fungus (Macrosporum Tobacinum E, & E.)
Another fungus of the same genus has been accredited in the same state as the
cause of brown-rot, but these have not been studied in Ohio.

TOMATO

Anthracnose (Colletotrichum phomoides (Sacc.) Chest.) occurs occasionally
upon tomato fruits, causing small depressed spots in them, The same fungus
may at times attack other parts of the plant. This disease seems to be checked
by the use of Bordeaux mixture. (See also Collar disease).

Bacterial Blight of the tomato, egg-plant and potato has already been men-
tioned. It was destructive at Mt. Carmel, near Cincinnati, in 1896 (B. 73). It
has since been locally.destructive. It causes sudden blighting and decaying of
the stems and branches attacked. Spraying has as yet proved useless for the
blight. Preventive measures recommended, include fighting insects, early
removal of diseased vines, choice of fresh land not previously in potatoes or egg-
plants, and tomato seed from healthy sources. To date this disease has been
less destructive than the leaf-spot.

Collar Disease Vermicularia sp. Recently a peculiar collar disease of fall
greenhouse tomatoes has come under study. In this case the symptoms were ab-
normal leaf development, after the manner of mosaic disease by artificial inoc-
ulation. The collar trouble was quite noticeable.

The case under study occurred in houses that appeared to be over-watered.
The plants set very little fruit and were not profitable. The root system appear-
ed to be normally developed except the adventitious whorl of roots near the sur-
face. Between these upper roots and the root crown below, thecollar of the plant

 
448 OHIO EXPERIMENT STA

is surrounded by a development of what appears to bea parasiticfungus, a spec-
ies of Vermicularia. The black masses of the fungus are also visible extending
down upon the root bases which are lighter in color. A similar abundance of
Vermicularia has been noted on the dead stems of potato tops which have died
from fusarium blight. :

This collar disease is just now under study. We believe something can be
accomplished by spraying with Bordeaux mixture about the base of the plants.
Certainly good will come by withholding excess water. This case of disease
was described where fusarium blight and mosaic disease also prevailed. The
fern-like leaf development is ascribed to the presence of the mosaic disease. The
association of the two diseases may be casual.

Leaf Mold (Cladosporium (?) fulvum Cooke) is a common trouble in tomato
forcing-houses in the fall or near the close of the season. It produces spots in the
leaves, while beneath they are covered by the grayish-brown mold fungus. The
fungicides heretofore recommended for use in the greenhouse are available for
the tomato leaf mold.

‘Leaf-Spot or Leaf-Blight is an
outdoor trouble, as is anthrac-
nose. The leaf-spot fungus (Sep-
toria Lycopersici Speg.) appears
to be gradually traveling west-
ward from the Atlantic coast,
where it first appeared several
years ago. During 1898 it was
locally disastrous over the whole
of Ohio, and again during 1900
and 1909. It may be successfully
prevented by about three thor-
ough sprayings with Bordeaux
mixture, though some difficulty
attaches to the treatment of un-
staked tomato plants in the field.
(Bulletins 73, 89, 105).

Mosaic disease attacks the to-
mato under conditions similar to
those giving trouble to cucumb-
ers, tobacco, etc. It is believed we

have a mosaic disease analogous

to that in tobacco and that the Fig. 97. Tomato leaflet and stem attacked by leaf-
spot. This causes dying of the leaves in showery seasons

 

 

remedy is pointed out by the
fact that the disease may be transmitted by touching first diseased and then
healthy plants.

The symptoms of the ordinary type of the disease are the alternation of
darker green and yellowish-green color in the leaves; this makes the plants con-
spicuous under ordinary circumstances. In 1909 with cases under glass, where
the collar disease appeared to be associated, abnormal leaf forms were observed
without very apparent intermixing of yellow areas in the leaves. The actual
leaf forms suggested the name of fern-leaf trouble. In these specimens the
internodes of the plants, the stems of the compound leaves and the petioles of
the leaflets were all elongated; the leaf-blades were narrowed at times to mere
borders along the mid-ribs. Gradations were also found between these extreme
DISEASES OF CULTIVATED PLANTS 449

forms and the normal leaves. Recent investigations by Westerdijk show the
disease to be distinct from the mosaic disease of tobacco though doubtless ana-
logous; the modified leaf forms were obtained by artificial inoculations both by
Westerdijk and in the Pathologium of this Station by Manns.

Nematodes may be very injurious to tomatoes grown under glass. They
Cause, as on cucumber plants attacked, gall-like enlargements on the small
roots of the tomato. Previous soil treatment to destroy the nematodes is the
remedy in this instance, as in the other. It will usually occur that tomato

plants are less susceptible to injury by nematodes than are cucumbers and
melons.

Point Rot of green tomatoes, especially in the forcing-house, is often the
most serious trouble with which the tomato grower under glass has to contend.
It was stated in Bulletin 73 that this trouble was observed to be most destructive
in cases of scant water supply in ‘the soil. This observation was again
confirmed by the Horticultural Department of the Station during the season
of 1899. The trouble was checked by abundant and careful watering, even
when it had been very bad, and was again produced by withholding water and
allowing the plants to dry out. The cause appears to be largely due to
conditions of drouth, and while other causes than the one just stated, notably a
certain bacterium does join to produce point rot, none other appears so under
control as water conditions. The remedy lies of course, in the avoidance of
drouth from which the rot may indirectly result.

Root-Rot or Rosette occurs frequently in
greenhouses where tomatoes are grown fol-
lowing crops of lettuce. The fungus produces
various effects which are commonly damping
off of the younger seedlings or collapse of the
older ones; recently a basal constriction of the
stem of mature plants is traced to Rhizoctonia.
In this case wilting of plants resulted. It
seems to be propagated under greenhouse
conditions where much organic matter is used
and calls for soil disinfection through steaming
or formalin drench as described elsewhere
under letiuce and under soil diseases. In
older plants the symptoms are _ shortened
development of the axis giving effects similar to
that in lettuce. . Fig. 98. Stems of young green-

Sclerotium Blight. This is a wilt disease house tomato plantsdamped off from
first reported by Rolfs from Florida but it is ttacks of “Rhizoctonia.” From a
now present in Ohio greenhouses. The first ali ail aca
symptom is wilting of terminal portion of plant. The dead plants and dis-
eased portions shows in them sclerotia of the fungus which causes the trouble.
These are of the size of mustard seed or smaller, at first milk white and finally
mahogony red to black. Sometimes these schlerotia grow together in anvil-
shaped masses. Burning diseased plants is advised.

 

 

 

 

 

Wilt. A wilt (Fusarium sp) of tomatoes in addition to that described under
bacterial disease has been discovered recently in greenhouses in Ohio as well as
otker states. It is due to a Fusarium.
450 OHIO EXPERIMENT STATION: BULLETIN 214

 

 

 

 

 

Fig. 99, Tomato fruits with browned and diseased spots in them.
This form of disease results from Fusarium Wilt of the plants; also
probably from Bacterial Wilt. From a photograph by T. F. Manns.

The symptoms of this wilt are rather characteristic. It may attack plants
either vigorous or of slow development. Commonly the first symptom noticed is
the yellowing and drying up of the lower leaves. Soon dark areas appear in
the stem and also in the fruits. At all stages cross sections show darkening of
vessels. The roots become darkened and watery in the region of the vessels.
Eventually the top of the plant wilts and the leaves die both above and below,
while the fruit has become worthless. We believe this to be a soil infesting dis-
ease that should be controlled by thorough soil sterilization.

 

Fig. 100. Similar fruits of green tomatoes spotted by effects of blight in Station greenhouses ©
in 1895, From Bulletin No, 73.
DISEASES OF CULTIVATED PLANTS 451

TURNIP

Black-Rot. The same bacterium attacks turnips as cabbage, cauliflower
and other mustards; the diseased roots show blackening of the parts with final
decay.

Club-Root. This fungus organism (Plasmodiophora Brassicae Wor.) infests
the roots of many cultivated mustard plants, including the turnip, radish,
rutabaga, etc. The treatment is the same as stated under cabbage.

Downy Mildew (Feronospora parasitica (Pers.) De By.) sometimes occurs
attacking turnip plants.

VERBENA /

Mildew. Cultivated verbenas are attacked by the mildew Zrysiphe
Cichoracearum DC) which is socommon on the wild vervains. It is to be
treated as other powdery mildews, by spraying with fungicides.

VERONICA

Leaf Diseases. Cultivated species of veronica are attacked by several leaf
dise: ses. which have been imperfectly studied. Perhaps the most common of
these is due tothe typical leaf-spot fungus (Septoria veronicae (Rob). There
are other parasitic species which attack the genus, including a downy mildew
and a rust.

VETCH

Spot. A spot disease (Protocoronospora nigricans Atk. and Edg.) has been
described as new from New York.

The Wilt of Vetch similar to that ofsoy beans, cow peas and cotton has also
been described.

VINCA

Leaf-Spot. The large flowered’ vinca is occasionally disfigured by a leaf-
spot (Sphaeropsis vincae Sacc.) which may also develop as a stem disease. It
has not beed studied carefully with us. *

VIOLET

Leaf-Spot and Leaf Blight (Phyllosticta Violae Desm. and Cercospora Violae
Sacc.) are sometimes prevalent, and with downy mildew of violet should yield
to spraying with fungicides.

Nematodes of violets are, on the other hand, not amenable to spray treat.
ment. The parasite in the case is the same as named under cucumber
nematodes, likewise its effects. Soil treatment will also be effective in
prevention here.

Root-Rot. Root-rot (Thielavia basicola Zopf.) has not been reported as
troublesome by greenhousemen in Ohio, but it is scarcely possible it can be
entirely lacking when the disease occurs upon tobacco and catalpa in fields.
The blackening and rotting of the roots, due to the fungus, will impair the
development of the plants and the flower growth seriously. It does not seem
possible that anything short of sterilizing the soil and starting new plants will
ckeck the root-rot where once established.

VIRGINIA CREEPER

Leaf-Spot. The leaves of virginia creeper are frequently curiously spotted
by a leaf-spot fungus (Phyllosticta labruscae Thim.) which gives dying spots with
colored border. This leaf-spot is also very common upon the Japan creeper
and is identical, according to recent reports, with the leaf-spot of the grape;
indeed we have a large number of the well known diseases of the grape at-
tacking the Virginia creeper. These include anthracnose, which may be
distinct, the black-rot fungus, of which this Phyllosticta may be a stage and
possibly others. This would be especially true in the vicinity of cultivated
grape vines. '
452 OHIO EXPERIMENT STATION: BULLETIN 214

WALNUT

Anthracnose or Leaf-Blight. The leaves of walnut, as well as the leaves of
butternut, are attacked by an anthracnose fungus (Marsonia juglandis Sacc.)
which in common with other anthracnoses, is’ capable of serious injury to the
leaves of these trees. It is believed that this fungus will be held in check by
sprays.

Leaf-Spot. The walnut is also attacked by other leaf fungi producing leaf
spots, but these have not been investigated by us in Ohio.

Mildew... The same powdery mildew which attacks a variety of trees
(Mycrosphaera alni DC.) also attacks the leaves of walnut, growing over and
forming a mildew covering.

WATERMELON

With the possible exception of the wilt disease and the leaf-spots, the diseases
of the watermelon are the same as those which attack cucumbers and musk-
melons. They include anthracnose, downy mildew and leaf blight. The leaf-spot
of the watermelon is referred to a distinct fungus (Cercospora citrullina Cke.)
though its ravages are, possibly, not general. (See Bulletins 73. 89, 105). In
the treatment of watermelon vines it is advisable to use the more dilute Bordeaux
mixture, Bordeaux II, of the calendar.

WHEAT

Anthracnose (Collettorichum
cereale Manns). In 1907 centrifuge
examinations were made by the
Assistant Botanist showing the
presence of anthracnose spores in
the washings of shriveled wheat
samples. The disease was dis-
covered in the fields generally ov-
er Ohio in 1908 and has recently
been described in Bulletin 203.
This anthracnose is certainly the
cause of shriveling in wheat. It
appears to be the obscure trouble
sought for some years by the
writer. In common with other
anthracnoses it develops as ma-
turity approaches and on wheat
it attacks the lower portions of |
the stems and sheaths resulting |
in apparent whitening of the
spikes with decided shriveling of
the grain. The fungus may be
detected by the color changes in
the field and by the dark spots
appearing on the sheaths and
stems where attacked. It is be-
lieved that thorough separation
of shriveled grain by recleaning
seed wheat and treatment of seed |
wheat with formaldehyde drench [i
will be favorable to keeping
down the amount of anthracnose. Fig. 101. Culms of wheat with both stems and
It is admitted that the presence sheaths attacked by anthracnose. The dark spots are

caused by the fungus. From Bulletin 203.
of the fungus upon grasses and

 

 

 

 

 

 
DISEASES OF CULTIVATED PLANTS

453

upon other cereals increases the danger of its being carried over in rotation. (See

tye, oats, timothy, also Bulletin 203.)

Lo ce
of the plants; on the right normal healthy kernels of wheat of the same
variety. From Bulletin 203.

Blade-Spot or Leaf-Spotting has occurred upon wheat in considerable extent
in Station plots during the last year or two. Small areas were killed by the
fungus and this leads to somewhat premature dying of the leaves This leaf dis-

ease calis for further investigations.

Grain Diseases. It must be remembered that an-
thracnose and scab are bothin a sense grain troubles.
They cause shriveling and loss of quality in the
grain. In addition afungus (4/teraria sp.) causing
dark spots in wheat kernels has been found by this
department. Scab must also be included here since
the parasite attacks the wheat kernels.

Powdery Mildew. This whitish fungus (Zrysiphe
gramiuis DC.) also appears upon leaves of wheat
plants. Usually it is of small importance in Ohio
but of much interest.

It attacks wheat both in pot cultures under glass
and in outdoor growth. In both cultures the conidial
development of the fungus is very troublesome invad-
ing the older leaves and causing prematuredeath. In
the field the consequences are usually not studied,
but the perithecia of the fungus are often found upon
straw blades and other parts that have been invaded.
It is clear that the fungus cannot be beneficiaFto the
development of the grain in attacked plants.

Scab. Thescab disease (Fusarium roseum Lk)
has been again investigated and the results published
in Bulletin No. 203. It has been found that the same
scab fungus attacks also rye, emmer, oats ard spelt,
producing the various effects upon these grains. On
all attacked heads in wheat the portion diseased
shows reddish or pink covering with the fungus and
the part of the spike above this is killed. Of course,
all kernels contained in that part are much shriveled
and are commonly invaded by the scab fungus. In attacked by scab.

 

Fig. 103. Wheat spike
The upper

addition a recent study showed that many various portion of the head isshrunken
sized kernels of wheat are infested with this fungus nd has been killed by the pink

internally, although still capable of starting to grow Foneus.

and making a new plant. Investigations made in
454 OHIO EXPERIMENT STATION: BULLETIN 214

culture dishes and greenhouse recently, show that the fungus survives in the
old dedd seeds as well asin some capable of germination and attacks the
seedling wheat plants during the first month of their growth. In the con-
tinuous wheat plots of the Station it was found that nearly 6 percent of the
plants were killed off in the unfertilized plots during 1907; the fertilized plots
show a good deal less and the rotation plots a great deal less (see Bulletin 203).
Not only may the fungus survive in its perithecial form upon wheat heads, straw
and dead scab grains, but it may survive in grain capable af germination as
well as in the soil. See pages 334-335. Recent studies of diseases of clover and
alfalfa seem to show that this same fungus is the cause of serious clover and
alfalfa sickness. It would thus appear to be carried over through rotations of
clover, etc. The best method of handling appears to be recleaning seed wheat and
getting out all shriveled kernels which are often scab-infested as well as all under
sized kernels thus evading a large share of the infection in seed wheat.

Seedling Blight. The seedlings of wheat are killed off by the attacks of the
scab fungus which is transmitted in the seed as well as in the soil devoted to
continuous wheat culture. (See scab above, also Bulletin 203.)

 

&

 

 

 

Fig, 104, On left, healthy normal kernels of wheat; on the right,
above kernels in ured by scab which will not germinate—below ker-
nels injured by weavil. From Bulletin 203.
DISEASES OF CULTIVATED PLANTS. 455

Loose Smut. This is a smut fungus (Us¢ilago
Tritict Jensen) which converts grain and glumes
into a sooty mass of spores. These heads of
loose smut are most obvious at the blossoming of
the wheat. The disease is worse on certain
varieties of wheat. It may be prevented by the
modified hot water treatment as per calendar.

Rust. While essentially the same to the
ordinary observer, the wheat rust is produced by
two rust fungi (Puccinia graminis Pers. & P.
rubigo-vera DC). Only the last named passes the
winter in the wheat plant. Both have the light
red and the black (dark) stages and are very
damaging under conditions which favor the rust.
In Europe, Australia, and California wheat
growers hope to select rust proof varieties of
wheat. Recently in England quite an impetus
has been given to wheat breeding by the work of
Biffen upon resistant varieties of wheat. This
resistance applies inthe English studies not only
to rust, but to some other features. The matter of
resistance is the hope of rust prevention. (See
Bulletin 97.)

Stinking Smut of wheat is caused by a still
more destructive smut fungus, (7Zilletia foetens
B & C) which converts the kernels of wheat into
dirty, stinking mass-
es of spores. These,
if abundant, ruin the

with the seed grain.

of wheat.

See Pine.

 

Fig. 106. Diseased and sound
spike of Poole wheat. In the one
atthe left the kernels have been
destroyed by Stinking smnt and
spikelets are spread abruptly.

 

Fig. 105. Heavy spike of
bearded wheat destroyed by
loose smut. These smut
spores are scattered and find
entrance into the forming
kernels of wheat when the
blooms open fer pc'tination.

flour and render the wheat valueless for human
food. At times 40 percent of the wheat is thus
destroyed and the losses from it are often very
large. Recent investigations have established
that this smut is caused by the smut spores sown
ee ai If the smutty seed wheat is
treated with a fungicide, such as bluestone, hot
water, formalin, etc.,
spores without injury to the grain and the treated
seed is then prevented from subsequent infection,
dried and sown, a clean crop may be grown from
smutted seed. For details of treatment see calen-
dar and Bulletin 97, which treats of the diseases

which will destroy these

WHITE PINE
456 OHIO EXPERIMENT STATION: BULLELIN 214

ADDENDUM

Corn, Root-Rot, (Fusarium sp.). Recently the Department has made pre-
liminary studies of a root-rot of corn attributed to a species of Fusarium of
similar behavior to the scab of wheat, potato fusarium and cabbage wilt, in
that the parasite appears to survive in the affected soil, as well as elsewhere.
From Fayette county comes the report of diseased corn roots in patches where
the stalks blow over easily, and rarely form mature ears. Roots of such plants
are partly killed and thus weaked. At present we can only advise rotation of
crops. More knowledge is needed with all this type of soil infesting diseases.

Raspberry, Cane Blight (New York). In reference to cane blight conditions,
page 437, this specific disease described by Stewart (Bul. 226, N. Y. Agric.
Expt. Sta., 1902) was not mentioned. Stewart identified the disease on speci-
mens sent to him from Ohio in 1902. Recently other specimens have been received’
from Cuyahoga and Wood counties. The earlier reference to cane blight forms
indicates how serious the raspberry condition is in Ohio. The parasite causing
the disease is Coniothyrium Fuckelii Sacc. The fungus attacks the plants kill-

ing and discoloring the bark and wood, thereby causing wilting of bearing
canes, and the ultimate death of the parts that have been attacked. The foliage
on affected canes wilts suddenly and becomes dry. The whole cane may be
involved, or only a part of it. At times a single branch is killed, while the
remaining cane continues apparently normal. It is feared that this disease is
very common in our unprofitable raspberry plantations in Ohio. The disease is
doubtless disseminated in plants from diseased plantations, and by the ordinary
agencies of wind, rain, etc. Naturally the dissemination by these last two
agencies is local. Preventive measures will include healthy plants, planting
on new uninfected land and a prompt cutting out and burning of old canes after
fruit is gathered. Stewart’s work indicates inconclusive results from spraying.
DISEASES OF CULTIVATED PLANTS

ee

LITERATURE OF PLANT DISEASES REFERRED TO
IN THIS PUBLICATION

GENERAL WORKS

1 Duccar,B.M. Fungous diseases of plants. 6508 pp. Ginn & Co., New York, etc., 1909.

2 Frank, A.B. Die Krankheiten der Pflanzen, (Diseases of Plants) 1, 2 and 3: pp. 344, 574 and
263, (3d Vol., Insect Parasites) 2d ed., Breslau, 1896; Edw. Trewendt.

3 Hartic, R. The diseases of trees, translated by Somerville & Ward. 331 pp. London 1894.

4 MassEE,G. Text-book of plant diseases. 458 pp, The MacMillan Co., New York, 1907.

5 PrILitieux, Ed. Maladies des plantes agricoles et des arbres fruitieres et forestiers causees par
des parasites vegetaux, 1: 421 pp. 2: 592 pp. Paris, 1897.

6 SmituH, W.G. Diseases of field and garden crops. 353 pp. 1884.

7 Soraver, PauL. Handbuch der Pflanzenkrankheiten, 3; (3d ed.) Diseases caused by plant
Parasites. 550 pp. Berlin; Paul Parey, 1908.

8 Tusevr, K. von, and SmirH, W.G. Diseases of plants induced by cryptogamic parasites.
598 pp. Longmans, Green & Co., London and New York, 1897.

9 Warp, H. MarsHav. Timber and some of its diseases. 295 pp. The MacMillan Co., N. Y., 1897.

10 Warp, H. MarsHatt. Disease in plants. 309 pp. The MacMillan Co., N.Y., 1901.

WORKS APPLYING TO PARTICULAR AREAS

ll Freeman, E.M. Minnesota plant diseases. 432 pp. St. Paul, 1905.

12 Hatsrep, B.D. Reports and Bulletins New Jersey Agr. Exp, Sta., 1889-1908.

13 Sevzy,A.D. A condensed handbook of diseases of cultivated plants in Ohio. Bul. Ohio Agr.
Exp. Sta., 121; 1-69, 1900.

14 Smirn, RatpH E. Reports of the Plant Pathologist (Calif.) 1906-1909. Buls. 184 and 203: Agri.
Expt. Sta., Berkeley, Calif.

15 Stewart, F.C. and Biopcert, F. H. A plant disease survey of the Hudson Valley in 1899.
Bul. New York Agr. Expt. Sta. 167: 273-308, 1899.

16 Srevens, F. L. and Hatt, J.G. Notes on plant diseases occurring in North Carolina. Rept.
N.C. Expt. Sta., 1908: 66-82.

17 Srurcis, W.C. Literature of fungous diseases. Rept. Conn. Agr. Expt. Sta. 1893; 253-286.
1897; 182-222.

18 Orton. W. A. Plant diseases in United States. Yearbook U.S. D. A. 1900: 729-731; 1901; 668-
674. 1902: 714-719; 1903: 550-556; 1904; 581-586; 1905: 602-611; 1906: 499-508; 1907: 577-589: 1908: 533-538.

19 Wiicox, E. M. and Stone, R. E. Directions for control of Nebraska plant diseases. Rept.
Neb. Agr. Expt. Sta., 22: 1909 . 27-93.

NAMING PLANT DISEASES

See Genera! and Local works listed above.

20 Orton, W. A. Plant diseases in the United States in 1907. Yearbook U.S. D. A. 1907: 577-589.

21 Srevens, F. L. Common names for plant diseases. Science N. S.. KXXI: 747, 1910 (May 13).
<See also earlier article on same subject).

DISEASE RESISTANCE IN PLANTS

22 Green, W.J. and Warp, C. W. Potato investigations. Theearly and late blight and how
tocombatthem. Bul. Ohio Agr. Exp. Sta. 174: 251-289.

23 Jones, L. R. Disease resistance of potatoes. Bul. Bur. Pl. Ind. U.S. D. A. 87: 1-39, 1905.

24 Oxrun, W. A. Development of farm crops resistant to disease. Yearbook U.S. D. A. 1908:
453-464.

25 Orton, W. A. and Wesser, H.J. A cowpea resistant to root-knot. Bul. Bur. Pl. Ind. U.
S. D. A. 17:38 pp. 1902. .

26 Orton, W. A. The wilt disease of cotton and its control. Bul. Div. of Veg. Physiology and
Pathology, U.S. D. A. 27: 1-16, 1900.

27 SruarT, WM. Disease resistance of potatoes. Bul. Vt. Agr. Expt. Sta. 122: 107-136; 1906.

METHODS OF {INOCULATION FROM CULTURES OF PARASITIC ORGANISMS

Smirtn, Erw. F. Bacteria in relation to plant diseases. 1: 108-109; 1905.
Buls. Ohio Agr. Exp. Sta. 203 and 210; 1909.

88
OHIO EXPERIMENT STATION: BULLETIN 214

ee
Pie

ENZYMATIC DISEASES

30 BrryertncK, W.M. Ueber ein Contagium vivum fluidum als Ursache der Fleckenkrankheit
der Tabaksblatter-Verhandelingen der Koninklijke Akademie van Wetenschappen te Amsterdam;
Deel 6, No. 5. See also Centb.f. Bakt. Par. &c., II, 5: 27-33; 1899 and Archiv. Neerl., 2Ser. III: 184, 1900.

31 Huncer, F, W. T. De mozaiek-ziekte bij deli-tabak, Deel I. Med. s’ Lands Plantentuin 63: 1903,

32 Huncer, F. W. T. Die Verbreitung der Mosaikkrankheit infolge der Behandlung des
Tabaks. Centbl. f. Bakt. Par. &c, II, 11: 405-408, 1904.

33 SeLsy, A. D. and Houser, TRUE. The mosaic disease of tobacco. Ohio Agr. Expt. Sta. Bul.
156: 91-95, 1904.

34 Woops, ALBERT F. The destruction of chlorophyll by oxidizing enzymes. Centbl. f. Bakt.
Par. &c. Il, 5: 745, 1899. x

35 Woops, ALBERTF. Observations on the mosaic disease of tobacco. U.S. D. A. Bul. Pl. Ind.
18; 1-24; 1902, i

PLANT DISEASES TRANSMITTED IN THE SEED

386 ARTHUR, J.C. Report of the Botanist New York Agr. Expt. Sta. 1884.
37 Barrus, M. F. The dissemination of disease by means of the seed of the host plant. Proc.
Ind. Acad. Sci., 1908: 113-122. :
38 Botztey, H. L. Scab of potatoes and beets. Buls. North Dakota Agr. Expt Sta. 4: 1891;
9: 1893; 19: 1895.
39 Bortey,H.L. A preliminary note on the cause of flax-sick soil, Fusarium Linisp. nov.
ProceedingsSoc. Prom. Agr. Sci. 22: 42-46; 1901.
40 Borvez, H. L. Flax wilt and flax-sick soil. Bul. North Dakota Agr. Expt. Sta. 50: 27-60; 1901.
41 Botiey, H. L. The use of the centrifuge in diagnosing plant diseases. Proc. Soc. Prom. Agr.
Sci. 21; 82-85; 1902. :
42 BreFELp, O. Recent investigations of smut fungi and smut diseases. (Translated) Jour. Myc.
VI: 59; 1890.
43 Brerewp, O.and FaccK,R. Die Bluteninfektion bei den Brandpilzen und die naturliche Verbreit-
ung der Brandkrankheiten. Gesamtgb. der Mykol. Heft. 13: 1-70; 1905.
44 Gussow, H. J. A serious potato disease occurring in Newfoundland (Canker or wart disease).
Bul. Cent. Exp. Farm, Ottawa, Can., 63: 1-8; 1909.
45 Jensen, J. L. The propagation and prevention of smut in oats and barley. Jour. Roy. Agr.
Soc. England, XXIV: part 2: 397-417; 1889.
- 46 KELLERMAN, W. A. Preliminary report on smut in oats. Rept. Kansas Agr. College, 2: 1889.
47 KELLERMAN, W. A. and SwIncLe, W. T. Prevention of smut in oats, etc. Buls: Kans. Agr.
Coll. 8: 1889; 15: 1890; 22: 1841.
48 KELLERMAN, W. A. Prevention of smut incereals. Agr. Sci. IV: 99; 1890.
49 Orton, W. A. Wart disease of the potato. Cir. Bul. Pl. Ind., U.S. D. A. 52: 1-11; 1910.
50 Sersy, A.D. The smut of oats and its prevention. Bul. Ohio Agr. Exp. Sta. 64; 115-139; 1895.
_ 6L Sgtsy, A.D. A rosette disease of potatoes attributed to the sterile fungus Rhizoctonia. Bul.
Ohio Agr. Expt. Sta. 139: 53-66, 1903. See aiso Bul. 145: 15-32; 1903.
52 Sev_ny, A. D. and Manns, T. F. Studies in diseases of cereals and grasses. Bul. Ohio Aer.
Expt Sta. 203: 187-216; 1909.
563 SmitH,E. F. and Swinctz, D. B. The dry-rot of potatoes due to Fusarium oxysporum, Bul.
Bur. Pl. Ind. U.S. D. A. 55: 1-64; 1904.
64 THaxTer, RoLAND. Potatoscab. Rept. Conn. Agr. Exp. Sta. 13: 3-17; 1889. 14; 81-95; 189).
65 VanHoox, J.M. Blighting of field and garden peas. Bul. Ohio Agr. Expt. Sta. 173: 231-
249; 1906.

SOIL INFESTING PARASITES r

See numbers 44, 51, 53, and 54, above.

Bolley, H. L. See numbers 38, 39, 40, and 41, above.

56 Green, W. J. Transplanting onions. Bul. Ohio Agr. Expt. Sta. Vol. III, No. 9: 244.

57 Sevry, A. D. Investigations of plant diseases in forcinghouse and garden. Bul. Ohio Agr.
Expt. Sta. 73: 221-246; 1896.

58 SeLpy, A.D. The prevention of onion smut. Buls. Ohio Agr. Expt. Sta. 122: 71-84; 1901; also
181; 47-51; 1902.

59 Sronz,G. A. and Smita, R.E. The rotting of greenhouse lettuce. Bul. Mass. Agr. Expt.
Sta. (Hatch) 69: 1-40; 1900.

60 Tuaxter, ROLAND. Oncertain fungus diseases of the onion, A//éum cepa, Rept. Conn Agr.
Expt. Sta. 13: 129-153; 1889.
DISEASES OF CULTIVATED PLANTS iii

SOIL TREATMENT

61 Rupp, W. N. Soil steaming. American Florist 9: 171; 1893. See also American Florist 10:
1038; 1895.

62 Srerzy, A.D. Soil treatment for the forcinghouse. Cir. Ohio Agr. Expt. Sta. 57: 1-7; 1906.

See also number 58 above.

63 SeLBy, A.D’ Soil treatment of tobacco plant beds. Cir. Ohio Agr. Expt. Sta. 59: 1-4; 1906.

64 Sevsy, A. D. Seed and soil treatments. Bul. Ohio Aur. Expt. Sta. 199: 95-96; 1908.

65 Samet, A. D. and Cosy, W. W. Methods of steaming tobacco beds. Bul. Bur. Pl. Ind. 91:
U.S. D. A. 1905.

ROOT DISEASES—ROOT-ROT FUNGI

66 Brices, L. J. Field treatment of tobacco root-rot. Cir. Bur. Pi. Ind. U.S. D. A. 7: 1-8; 1908.

67 GriBEertT, W.W. The root-rot of tobacco caused by Threlavia basicola, Bul. Bur. Pl. Ind., U-
S.D. A. 158: 1-55; 1909. Contains Bibliography.

68 SeLBy, A. D. Root-rot diseases of peach. Bul. Ohio Agr. Expt. Sta. 92: 235; 1898.

69 SrLBy, A.D. Root-rot of tobacco. Bul. Ohio Agr. Expt. Sta. 156; 93-97; 190.

70 Smits, E.F. The root-rot of peach. Journ. Mycology. 7: 377; 1894.

71 THaxtTer, Rovanp. Root-rot of violets. Rept. Conn. Agri. Expt. Sta. 15: 166-167; 1891.

72 Wiicox, E. M. Rhizomorphic root-rot of fruit trees. Bul. Okla. Agr. Expt. Sta. 49: 132; 1901.

WOUNDS AND WOUND PARASITES

FREEMAN, E. M. See number 11.

73 ScHRENK, H. von. The decay of timber and methods of preventing it. Bul. Bur. Pl. Ind. U.
S. D. A. 14; 1-96; 1902. ;

74 Scurenk H. von. A disease of the white ash caused by Polyporus fraxinophilus, Bul. Bur.
Pl. Ind., U.S. D. A. 32: 1.20; 1903.

75 ScHRENK, H. von. Sap-rot and other diseases of the red gum. Bul. Bur. Pl. Ind. U. S.D. A.
114; 1-34; 1907.

FUNGICIDES

76 CRANDALL, C.S. Bordeaux mixture. Bul. Il. Agr. Expt. Sta. 135: 200-296; 1909. (Contains
full references to literature).

77 Farrcuitp, D.G. Bordeaux mixture. Bul. Div. Veg. Path. and Phys., U.S. D.A.,6:
1-55, 1904. .

78 GREEN, W. J. The spraying of orchards. Bul. Ohio Agr. Expt. Sta. Vol. IV: No. 9: 193-220;
1891.

79 Hevricx, U.P. Bordeaux injury. Bul. N. Y. Agr. Expt. Sta. 287: 217-286; 1908.

80 LopemMan, E.G. Thespraying of plants. 1-110; 1896.

81 MrtuarpeT, A. Jour. d’Agr. Prat. October 8, 1885: 513-514.

82 PappocK, WENDELL. Spray pumps and spraying. Bul. N. Y. Agr. Expt. Sta. 121: 196
219; 1897.

83 PrcKERING, U. Bordeaux mixture (Chemical composition) Jour. Chem. Soc. London. Vols.
XCI, XCII; 1907: 1988-2001.

84 Scott, W. M. Self-boiled lime-sulfur as a promising fungicide. Cir. Bur. Pl. Ind. U.S. D.
A. 1: 1-18; 1908.

85 Scotr, W.M. The substitution of lime-sulfur preparations for Bordeaux mixture in the treat-
ment of apple diseases. Cir. Bur. Pl. Ind. U.S. D. A. 54: 1-15; 1910.

86 Scotr, W.M. Lime-sulfur mixtures for the summer spraying of orchards. Cir. Bur. Pl.
Ind. U.S. D. A. 27: 1-17; 1909. :

87 SEeLBy, A.D. Two promising fungicides. Cir. Ohio Agr. Expt. Sta. 87: 6-8; 1908.

88 Sexsy, A.D. and Hicks, J. F. Soda-Bordeaux mixture. Bul. Ohio Agr. Expt. Sta. 130:
35-40; 1902.

89 SwincLe, W. T. Bordeaux mixture: Its chemistry, physical properties and toxic effects.
Bul. Div. Veg. Phys. and Path. U.S. D. A. 9:1-37; 1896.

90 Warre,M.B. Fungicides and their use in preventing diseases of fruits. Farmers Bul. U.S.
D. A. 243: 1-32; 1906.

DISEASES OF POME FRUITS

91 Axtwoop, W. B. Ripe-rot or bitter-rot of apples. Bul. Virginia Agr. Expt. Sta. 40: 59-82; 1894.

92 ArtHuR, J.C. Report of Botanist, Pept. N. Y. Agr. Expt. Sta. 3: (1884) 351-385; 1885.

93 ARTHUR, J.C. Histology and biology of pear blight. Proc. Phil. Acad. Nat. Sci. 1886:
322-341. ; .

94 Brarr, Jos. C. Bitter-rot of apples, Horticultural investigations. Bul. Ill. Expt. Sta. 117:
483-551; 1907.

95 Burriut, T. J. Bitter-rotof apples. Bul. Ill. Expt. Sta. 77: 351-366; 1902.
iv OHIO EXPERIMENT STATION: BULLETIN 214

fe $§ Burrru, T. J. Bitter-rot of apples. Botanical investigations. Bul. Ill. Expt. Sta. 118: 556-
; 1907.

97 Burritt, T.J. Pear blight. Trans. Ill. State Hort. Soc. 1877; 114; 1878: 80.

98 Burritt, T. J. Pear blight. Proc. Am. Assn. Adv. Sci. 29: 583; 1880.

99 CxuinToN, Geo. P. Apple rots in I!linois. Bul. Ill. Expt. Sta. 69: 189-224; 1902.

100 Dermers, F. Applescab. Bul.Ohio Agr. Expt Sta. Vol. IV, No. 9: 187-192; 1891.

101 Hatstep, B.D. The black-rot of the quince. Bul. N. J. Agr. Expt. Sta. 91: 8-10: 1892.

102 Hassecsrinc, H. Canker of apple trees. Bul. Ill. Expt. Sta. 70: 225-239; 1902.

103 Lopeman, E.G. The sprayings of orchards: Bul. Cornell Agri. Expt. Sta. 80; 47-74, 1895.

104 Pappocx, W. The New York apple tree canker. Bul. N.Y. Agr. Expt. Sta. 163; 179-261, 1899;
also 185: 205-213; 1900. :

105 Scurenx, H. von. and Spautpine, P. The bitter-rot of apples. Bul. Bur. Pl. Ind. U.S.
D. A. 44: 1-29; 1903. Contains complete literature list.

106 Scorr, W.M. Thecontrol of apple bitter-rot. Bul. Bur. Pl. Ind. U.S. D. A. 93: 1-36; 1906.

107 Scott, W. M. and Rowrer, J. B. Apple leaf-spot caused by Sphaeropsis malorum, Bul. Bur.
Pl. Ind. U.S. D. A. 121: 46-54; 1908.

108 Sexrzy, A.D. Bitter-rot, sooty and fly-speck fungus on apple. Bul. Ohio Agr. Expt. Sta.
79: 133-136; 1897. :

109 Sersy, A.D. Fall and early winter injuries to orchard trees and shrubbery by freezing. Bul.
Obio Agr. Expt. Sta. 192: 129-148; 1908.

110 SourHworTH, E. A. Ripe-rot of grapes and apples. Jour. of Mycology, 6; 164-173; 1891.

111 Srurers, W. C. Ripe-rot or bitter-rot. Bul. Conn. Agr. Expt. Sta. 111: 1-5; 1892.

2 Tart, L. R. Theripe-rot or bitter-rot of the apple. (Gloeosporium fructigenum Berk.) Bul.
Mich. Agr. Expt. Sta. 121; 21, 46-47; 1895.

113 Wartre,M.B. Treatment of pear leaf-blight in the orchard. Jour. Mycol., 7: 333-338, 1894.

114 Waite, M. B. Cause and prevention of pear blight. Yearbook U.S. D. A. 1895: 295-300.

115 Wuetzerk, H. H. The blight canker of apple trees. Bul. Cornell University Expt. Sta. 236
“03-138; 1907.

DISEASES OF STONE FRUITS

116 ArTHuR,J.C. Plum-leaf fungus. Rept. N. Y. Agr. Expt. Sta. 8: 293-298; 1889.

117 Arxinson,G. F. Leaf.curl and plum pockets. Bul. Cornell Univ. Agr. Expt. Sta. 78: 319-
353.

118 Beacu,S. A. Plum leaf-spot; Cherry leaf-spot and fruit-rot. Buls. N. Y. Agr. Expt. Sta.
98: 1-31, 1896; 117: 132-151, 1897.

119 Duccar, B. M. Peach leaf-curl. Bul. Cornell Agr. Expt. Sta. 164: 371-388; 1899.

120 Fartow, W.G. The black knot. Bul. Bussey Institution, 1876: 440-453.

121 Humpnurey,J.E. The black-knot of the plum. Rept. Mass. Agr. Expt. Sta. 8: 200-210; 1890.

122 Humpurey,J.E. On Monilia fructigena. Bot. Gaz. 18: 85-93; 1893.

123 Norton, J. B.S. Sclerotinia fructigena. Trans. Acad. Sci. of St. Louis, 12: 91-97; 1902.

124 Pierce, N.B. Peach leaf curl: Itsnature and treatment. Bul. Div. Veg. Path. and Phys.,
U.S. D. A. 20: 1-204; 1900.

125 SeLsy, A.D. Preliminary report upon diseases of the peach. Bul. Ohio Agr. Expt. Sta. 92:
226-231;1898. See also 104: 201-216, 1899, and 148: 55-68, 1904.

126 SeLzsy, A.D. Variation in the amount of leaf-curl of the peach in the light of weather con-
ditions. Proc. Soc. Prom. Agr. Sci. 20: 98-104; 1899.

127 Situ, Erw. F. Peach blight, Montlia fructigena Pers. Jour. Mycol. 5: 123-134, 1889.

128 Situ, Erw. F. Peach yellows: Its cause and control. Bul. Sect. Veg. Path., U.S.D. A.
9: 1-254; 1888. Also Bul. Div. Veg. Path. 1; 58; 1891.

129 Srewart, F. C. and Eustace, H. J. Shot-hole fungus on cherry fruit pedicles. Rept. N. Y.
Agr. Expt. Sta. 20: 146-148; 1901.

DISEASES OF SMALL FRUITS

130 Drtmers, FrepDA. Diseases of the blackberry and raspberry. Bul. Ohio Agr. Expt. Sta. Vol.
IV, No. 6: 124-129; 1891.

131 Duranp, E. J. A disease of currant canes. Bul. Cornell Univ. Agr. Expt. Sta. 125: 23-38; 1897.

132 Gattoway, B. T. Experiments made in 1888 in the treatment of the downy mildew and black-
rot of the grape-vine. Sect. Veg. Path. U.S. D. A. 10: 1-61; 1889; see also 11: 1-119; 1890.

133 PamMEL, L. H. Spot diseases of currants and gooseberries. Bul. Iowa Agr. Expt. Sta. 18:
67-70; 1891.

134 Reppicx,D. The black-rot of the grape and its control. Bul. Cornell Univ. Agr. Expt. Sta.
253: 367-388; 1908.

135 ScrrpNer, F. L. Anthracnose of raspberry and blackberry. Rept. U.S. D. A. 1887: 357-367.

136 Scrrpner, F. L. The fungus diseases of the grape-vine. Bul. Div. Bot., U. S. D. A. 2:28
84; 1886.

137 SeLBy, A. D. Diseases of currants and gooseberries. Bul. Ohio Agr. Expt. Sta. 7J: 102-112; 1897.

138 SeLby, A. D. Grape-rots in Ohio. Bul. Ohio Agr. Expt. Sta. 123; 85-94; 1901.
DISEASES OF CULTIVATED PLANTS v

139 Sezy, A. D. and Hicks, J. F. Experiments in the prevention of grape-rot. Bul. Ohio Agr.
Expt. Sta. 123: 94-102; 1901.
‘4 an Setpy, A. D. and Hicks, J. F. Spraying for grape-rot. Bul. Ohio. Agr. Expt. Sta. 130: 29-

141 Srewart, F. C. and Eustace, H. J. Anepidemic of currant anthracnose. Bul. N. Y. Agr.
Expt. Sta. 199: 63-80; 1901.

142 Stewart, F.C. and Eustace, H. J. Raspberry cane-blight and raspberry yellows. Bul. N.
Y. Agr. Expt. Sta. 226: 331-364; 1902.

DISEASES OF POTATO, TOBACCO, TOMATO, EGG-PLANT, ETC.

143 Ciinton,G. P. Downy mildew or blight, Phytophthora infestans (Mont.) DeBy.. of potatoes.
Rept. Conn. Agr. Expt. Sta. 1904 363-384. 1905:304-330.

144 Ciinton,G. P. Root-rot of tobacco. Rept. Conn. Agr. Expt. Sta. 1906: 342-368.

145 Ducear, B. E. and Stewart, F. C. Thesterile fungus Rhizoctonia. Bul. Cornell Expt. Sta.
186: 50-76; 1901. Aliso Bul. N. Y. Agr. Expt. Sta. 186: 3430: 1901.

146 GivzertT, W. W. The root-rot of tobacco caused by Thielavia basicola, Bul. Bur. Pl. Ind.,
U.S. D. A. 158: 1-55; 1909. Contains full literature list.

147 Hatstep, B. D. Some fungous diseases of the egg-plant. Rept. N. J. Agr. Expt. Sta. 12: 277-
279; 1891.

148 Jones, L.R. Certain potato diseases and their remedies. Bul. Vt. Agr. Expt. Sta. 72:
13-16; 1899. ;

149 Jones, L. R. Diseases resistance of potatoes. Bul. Bur. Pl. Ind. U. S.D. A. 87: 1-39: 1905.

150 Orton, W. A. Potato failures in San Joaquin Valley, California. Cir. Bur. Pl. Ind. U.
S. D. A.. 23: 1-14; 1909.

151 Rotrs, F. M. Potato failures. Bul. Colo. Agr. Expt. Sta. 70: 1-20; 1902. Also 91: 1-33; 1904.

152 Roxurs, P. H. Tomato diseases. Bul. Fla. Agr. Expt. Sta. 91: 15-34; 1907. _

153 Sevsy, A. D. On the occurrence of Phytophthora infestans and Plasmopara cubensis in Ohio.
Ohio Naturalist, 7: 79-85; 1907. See also No. 51.

154 SeLsy, A. D. Tobacco diseases in Ohio. Bul. Ohio Agr. Expt Sta. 156: 87-107; 1904.

155 Setsy, A. D. ‘Tomato diseases. Bul. Ohio Agr. Expt. Sta. 78: 237-245; 1896. Also 105:
232-234; 1899. See also No. 13. :

156 Smiru, E. F. A bacterial disease of the tomato, egg-plant and Irish potato. Bul. Div.
Veg. Path. and Phys., U. S. D. A. 12; 1-26; 1896.

157 Smits, E. F. The Granville tobacco wilt. Bul. Bur. Pl. Ind., U.S. D. A. 141: 17-24; 1908.

158 SmitH, E. F. and Swinciez, D. B. The dry-rot of potatoes due to Fusarium Oxysporum,
Bul. Bur. Pl. Ind., U. S. D. A. 55: 1-64; 1904.

159 Srevens, F. L. and Sackett, W. G. The Granville tobacco wilt. Bul. N. C. Agr. Expt.
Sta. 188: 1903. pa

160 Srewart, F. C. Potato diseases on Long Island in the season of 1895. Bul. N. Y. Agr.
Expt. Sta. 101: 72-86; 1896.

161 Stewart, F. C. Spraying potatoes on Long Island in the season of 1896. Bul. N. Y. Agr.
Expt. Sta. 123; 234-259; 1897.

162 Srewart, F. C., Eustace, H. J. and Srrring, F. A. Potato spraying experiments in 1906.
Bul. N. Y. Agric. Expt. Sta. 279: 154-229. The same 296: 307-311.

 

DISEASES OF VEGETABLE AND FIELD CROPS (EXCEPT SOLANACEOUS PLANTS)

163 ArtTHUR' J. C. Lettuce mildew. Rept. N. Y. Agr. Expt. Sta. 4: 253-254; 1885.

164 Beacu, S. A. Bean anthracnose and its treatment. Rept. N. Y. Agr. Expt. Sta. 11:
531-552; 1892.

165 Fuiton, H. R. Bean diseases. Bul. La. Expt. Sta. 101; 9-13; 1908.

166 GaLLoway, B. T. A record of some of the work of the division. Bul. Div. of Bot. U. S.
D. A. (Sec. of Veg. Path.) 8: Part II: 41-67; 1889.

167 Hatsrep, B. D. The asparagus rust; its treatment and naturalenemies. Bul. N. J. Agr,
Expt. Sta. 129: 1-20; 1898.

168 Hatstep, B. D. Laboratory study of fruit decays. Rept. N. J. Agr. Sta. 13: 326-333; 1892.

169 Hatstep, B. D. Club-root of cabbage and its allies. Bul. N. J. Agr. Expt. Sta. 98: 1-16.
1893. 3

170 Hatstep, B. D. Some fungous diseases of the sweet potato. Bul. N. J. Agr. Expt. Sta.
76: 1-32: 1890.

171 Hausrep, B. D. and Farrcarip, D. G. Sweet potato black-rot. Jour. Myc, 7: 1-11; 1891.

172 Humpurey, J. E. The cucumber mildew. Rept. Mass. Agr. Expt. Sta. 8: 210-212; 1890.

173 PammMet, L. H. Preliminary notes on root-rot disease of sugar beets. Bul. Iowa Agr.
Expt. Sta. 15: 243-251; 1891.
:

vi OHIO EXPERIMENT STATION: BULLETIN 214

174. Pammet, L. H. Bacteriosis of ruta-baga’ Bul. Iowa Agr. Expt. Sta. 27: 130-135; 1895.

175 RussELt, H. Ll. Bacterial rot of cabbage and allied plants. Bul. Wis. Agr. Expt. Sta.
65: 1-39; 1898.

176 Scrrpner. F, L. Anthracnose of the bean. Rept. Sec. Veg. Path., U.S. D. A., 1887:
361-364.

177 Sevny, A. D. Diseases of cucurbits. Bwl. Ohio Agr. Expt. Sta. 89; 1897 and 105; 1899.

178 Sexzy, A. D. Additional host plants of Plasmopara cubensis, Bot. Gaz. XXVII: 67-68:
1899.

179 Sersy, A. D. Lettuce leaf perforation and other lettuce diseases. Bul. Ohio Agr. Expt.
Sta. 73: 222-226; 1896.

180 Sexsy, A, D. A rosette disease of lettuce. Cir. Ohio Agr. Expt. Sta. 57: 1-7; 1906.

181 Seisy, A. D. Onion smut and its prevention. Buls. Ohio Agr. Expt. Sta. 122: 71-84; 1900,
181; 47-52; 1902.

182 SmitH, Erw. F. The black-rot of cabbage. Farmers’ Bul. U.S. D. A. 68: 1-21; 1898,
See also Centrbl. f. Bakt. Parask. u. Infektkr. 3: (II. Abt.) 1897. : .

183 Situ, R. E. Botrytis and Sclerotinia: Their relation to certain plant diseases and to each
other. Bot. Gaz. XXIX: 389-407; 1900.

184 Stewart, F. C. Downy mildew of the cucumber: What it is and how to prevent it. Bul.
N.Y. Agr. Expt. Sta. 119: 154-183; 1897. ss

185 Srone, G. E. and SmituH, R.E. “Drop” of lettuce. Rept. Mass. Agr. Expt. Sta. 9: 79-
81; 1897.

186 Strurcis, W. C. The mildew of lima beans. Rept. Conn Agri. Expt. Sta. 1997: 159-166.
Also Bot. Gaz. XXV: 191-194; 1898.

187 Tuaxter, R. Mildew of lima beans. Rept. Conn. Agr. Expt. Sta. 13: 167-171; 1889.

188 THaxter, R. Diseases of the onion. Rept. Conn. Agri. Expt. Sta. 13: 129-166; 1889.

VanHoox, J. M. See No. 55.

189 WuetzEL, H. H. Some diseases of beans. Bul. Cornell Agr. Expt. Sta. 239: 198-214, 1906.

DISEASES OF CEREALS AND GRASSES

190 ArtHuR, J. C. The rusts (Uredineales). North Am. Flora 7: 83-160; et sea.

191 Manns, T. F. The blade blight of oats; a bacterial disease. Bul. Ohio Agr. Expt. Sta.
210: 91-167; 1909. .

192 Sexsy, A. D. Some diseases of wheat and oats. Bul. Ohio Agr. Expt. Sta. 97: 31-61, 1898.

193 Sexvpy, A. D. and Manns, T. F. Studies in diseases of cereals and grasses. Bul. Ohio Agr.
Expt. Sta. 203: 187-236; 1909.

194 Srewart, F. C. A bacterial disease of sweet corn. Bul. N. Y. Agr. Expt. Sta. 180: 423-
439; 1897.

DISEASES OF FORAGE CROPS

195 Barn, S. M. and Essary, S. H. <A new anthracnose of alfalfa and red clover. Jour. Myc.
12: 192-193; 1908.

196 Barn, S. M. and Essary, S. H. Selection for disease-resistant clover. Bul. Tenn. Agr.
Expt. Sta. 75: 1-10; 1906.

197 Cuestrer, F. D. Clover diseases. Rept. Del. Agr. Expt. Sta. 8: 79-88; 1890.

198 Comss, Rost. The alfalfa leaf-spot disease. Bul. Iowa Agr. Expt. Sta. 36: 858-859; 1897.

199 Pam™et, L. H. Clover rust. Bul. Jowa Agr. Expt. Sta. 13: 51-55; 1891.

200 Sackett, W. G. A bacterial disease of alfalfa. Bul. Colo. Agr. Expt. Sta. 158: 1-32; 1910.

201 SeLBy, A. D. and Manns, T. F. Studies in diseases of cereals and grasses. Bul. Ohio Agr.
Expt. Sta. 203: 187-236; 1909.

DISEASES OF FOREST AND SHADE TREES

202 ATKINSON, GEO. F. Studies of some shade tree and timber destroying fungi. Bul, Cornel:
Agr. Expt. Sta. 193: 199-235: 1901.

203 Epcerton, C. W. The physiology and development of some anthracnoses, including one on
sycamore. Bot. Gaz. 45: 367-408; 1908.

204 Kiesann, H. Unters. uber einige Fungi imperfecti u.d. zugehoregen Ascomycetenformen.
Jahrb. f. wiss. Bot. 41: 515-558; 1905. .

205 Metcatr, Haven. Diseases of ornamental trees. Yearbook, U. S. D. A. 1907: 483-494.

206 ScHRENK, H. von. Two diseases of red cedar. Bul. Div. Veg. Phys. and Path. U. S. D.
A. 21: 1-22; 1900. F :

207 ScHRENK, H. von. Some diseases of New England conifers. Bul. Div. Veg. Phys. and
Path. U. S. D. A. 25: 1-56, 1900. :
DISEASES OF CULTIVATED PLANTS vii

208 ScHRENK, H. von. Fungus diseases of forest trees. Yearbook U. S. D. A. 1900: 199-210.

209 ScHrENK, H. von. A disease of the white ash caused by Polyporus fraxinopholus, Bul.
Bur. Pl. Ind. U. S. D. A.. 82: 1-18; 1903.

210 ScHreNK, H. von. A disease of the black locust (Robinia pseudacacia L.). Rept. Missouri
Bot. Garden 12: 21-31; 1901. e

211 ScHrenK, H. von. and Spautpine, P. Diseases of deciduous forest trees. Bul. Bur Pl.
Ind. U. S. D. A. 149: 1-85; 1909. (Contains complete literature list).

212 SpauLpinc, Pertey. The treatment of damping off in coniferous seedlings. Cir. Bur. Pl.
Ind. 4: 1-8; 1908.

213 Scripner, F. L. A disease of sycamore. Rept. U.S. D. A. 1888: 387-389.

214 SoutHwortH, E. A. Gloeosporium nerviseqguum (Fckl.) Sacc. on sycamore. Jour. Myc. 5:
61-52: 1889.

215 Woops, A. F. and Gattoway, B. T. Diseases of shade and ornamental trees. Yearbook,
U.S. D. A. 1896: 237-254.

DISEASES OF ORNAMENTAL PLANTS

216 ArTHUR,J. C. Chrysanthemum rust. Bul. Ind. Agr. Expt. Sta. 85: 145-150; 1900.

217: ATKINson, G. F. A new anthracnose of privet. Bul. Cornell Agr. Expt. Sta. 49: 306-314;
1892.

218 Duptey, W. R. The hollyhock rust. Bul. Cornell Agr. Expt. Sta. 25: 154-155; 1890.

219 Haustep, B. D. Repts. N. J. Agr. Expt. Sta. 11; 1890; 12: 1891; 18: 1892; 14: 1893. Gives
descriptions of diseases of many ornamental plants.

220 Heap, F. D. The bud rot of carnations. Bul. Neb. Agr. Expt. Sta. 103: 1-8; 1908.

221 MurrILyt, W. A. A serious chestnut disease (bark disease). Jour. N.Y. Bot. Gaz. 7: 143-
153; 1906. Also 7: 203-211; 1906.

222 Smiru,E. F. Wakker’s hyacinth germ. Bul. Div. Veg. Phys. and Path. U.S. D. A.
26: 1-45; 1901. Also Bul. 28: 1-153; 1901.

223 Srewart, F. C. Combating carnation rust. Bul. N. Y. Agr. Expt. Sta. 100: 32-68; 1896.

224 Stewart, F. C. An anthracnose and a stem rot of cultivated snap-dragon. Bul. N. Y.
Agr. Expt. Sta. 179: 105-110; 1900.

225 Stewart, F. C. and Hopexriss, H. E. The bud rot of carnations and the silver top of
June grass. Tech. Bul. N. Y. Agr. Expt. Sta. 7: 83-119; 1908.

226 Townsenp, C. O. A soft rot of the calla lily. Bul. Bur Pl. Ind. U. S. D. A. 60: 1-44; 1904.