TEXAS AGRICULTURAL EXPERIMENT STATION

A. B. CONNER, DIRECTOR
College Station. Texas

BULLETIN NO. 623 NOVEMBER 1942

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CONTROL OF EGGPLANT YELLOWS i

S. E. JONES

Division of Entomology

 

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AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS
T. O. WALTON, President

B25-1142—6M-L180

Eggplants grown during the late summer and fall months in South
and Central Texas are usually affected with a disease commonly called
“eggplant yellows,” which may cause most of the plants in a field to turn
yellow and fail to bear a full crop. Conspicuous yellow spots first ap-
pear on the young leaves in the terminal buds. These areas increase in
size, frequently following the veins, and gradually destroy the green
color in the plant. The contrast of yellow and green in an eggplant field
is apparent at a considerable distance. The disease is infectious and
appears t0 be caused by a virus, but the method of natural transmission
is not yet known.

The most practical control of eggplant yellows was obtained by keep-
ing the plants lightly covered with sulfur dust throughout the tinle they
were in the seedbed. This treatment plus two or more dust applications
after the plants were set in the field gave even better control of the di-
sease, but. the additional applications were not found profitable. Satis-
factory control of eggplant yellows was not obtained when dusting was
begun after the disease appeared in the field.

CONTENTS

Page

Introduction 5
Review of Literature  5
Symptoms" of Eggplant Yellows 6
Experimental Procedure 7
Results 3
Effects 0f various dusts 8
Time of application 9
Other treatments 9
Transmission of Eggplant Yellows 11
Grafts 13
Artificial inoculation 12
Insects 11
Discussion 14
Control Recommendations 14
Summary 16
Literature Cited 17

CONTROL OF EGGPLANT YELLOWS

S. E. Jones,* Entomologist
Division of Entomology

Eggplant growers throughout south and central Texas_ are familiar
with a disease which causes th-e plants to turn yellow and fail to fruit
normally. Scattered plants may develop the conspicuous yellow color
soon after transplanting and by the end of the season most of them
may be diseased. Soil and cultural conditions seem to have little or
no relationship to the prevalence of the disease, except that stunted
plants are usually less likely to become infected than rapidly growing
plants. Eggplants grown on new ground or isolated many miles from
other‘ plantings may be just as severely damaged as where the crop
is grown continuously on on-e farm. Scattered plants here and there
turn yellow while adjoining plants may remain healthy throughout the
season. The disease is usually more prevalent in the fall than in the
spring or early summer.

REVIEW OF LITERATURE

The first mention of eggplant yellows in scientific literature was made
by Taubenhaus" and Hawthorn (11) in 1933. They gave a brief de-
scription of the disease and stated that it was very common in South
Texas and to a less extent wherever eggplants are grown in the state.
Hawthorn and Taubenhaus (1) reported the following: “A series of
treatments involving soil amendments such‘ as sulphur, iron sulphate,
and superphosphate in various amounts and combinations, failed to cor-
rect the condition or prevent its spread. Likewise dusting with sulphur,
as well as spraying with iron sulphate in various dilutions, failed to pro-
duce any response.” The disease was transmitted in 3 out of 7 trials
when infected buds were grafted on healthy plants by Taubenhaus and
Hawthorn (12) who reported: “From the evidence on hand, it appears
that eggplant ‘yellows’ is probably of a virus nature, and for this rea-
son was unaffected by the sulphur or iron sulphate treatments”. In
later tests Taubenhaus (10) reported that 6 out‘ of 10 grafted plants be-
came infected. Ivanoff (2) in recent studies obtained additional infor-
mation on the nature of the disease, which is discussed in this publication.

Jones and Janes (7)-first reported that remarkable and satisfactory
control of eggplant yellows was" obtained by dusting the plants with a
rotenone-sulfur mixture, beginning while the plants were in the seedling
stage and before infection took place. Growing the seedlings under
screen cages to protect them from insects was of some benefit. They

*Appointed Superintendent of Substation 17, Ysleta, January 1, 1942. M. J.
Janes was in charge of these investigations in 1936 and 1937 during the author's
absence. Thanks are also givin to W. H. Mecom and T. B. Randolph for assistance
in conducting some of the field control experiments.

6 BULLETIN NO. 623, TEXAS AGRICULTURAL EXPERIMENT STATION

Figure 1. Three plants showing various stages of eggplant yellows disease. Plant
on left has shown symptoms for about one week. Note lower branch
still healthy. Center plant has had the disease for about three weeks.
Plant on the right has had the disease for about two weeks. Note pat-
tern of yellow color in leaves.

suspected that certain insects are carriers of the disease. Further suc-
cess in controlling the disease was reported by Janes (4), Jones (5, 6),
and Randolph (9). i

In an effort to determine the distribution of eggplant yellows outside
of Texas the picture used in figure 1, together with a description of the
disease, was sent to horticulturists and plant pathologists in Alabama,
Arizona, Arkansas, California, Florida, Georgia, Louisiana, Mississippi,
New Mexico, Oklahoma, Oregon, and South Carolina. What is said to
be this disease was reported from Florida, Louisiana, Oklahoma, and
South Carolina. A number of agricultural workers from northern states
who have seen eggplant yellows in Texas reported that they had never
seen it anywhere in the North.

SYMPTOMS OF EGGPLANT YELLOWS

The first symptom of the disease is the appearance of greenish-yellow
spots in young leaves. These spots increase rapidly in size and frequent-
ly follow the veins until the entire leaf is yellow. The disease pro-
gre-sses down the branch until all leaves are affected (Fig. 1). Another
branch will later exhibit the symptoms, always starting in the bud and

\|

CONTROL OF EGGPLANT YELLOWS

passing downward. The color of the diseased areas is‘ first greenish-
yellow, then orange-yellow, and finally almost white before the plant
dies. It takes about 25 days for a plant to become completely yellow
after the first symptoms appear, probably depending on the stage and
rate of growth of the plant, temperature, moisture, and. perhaps other
factors. The disease first appeared in the experimental plots 2 to 4
weeks after the plants were set in the field during August. The period
of most rapid spread usually occurred 6 to 10 weeks after transplanting.
Plants infected early in the season usually die before fruiting, while
those not taking the disease until later may bear some fruit. Since
green tissue is necessary for growth and fruiting of eggplants, it is
thought that the damage is in proportion to the amount of foliage af-
fected and the stage of growth when infection occurs. Infected plants
have never been observed to recover from the disease even though they
may live through the winter and put out new foliage in the spring. The
leaves do not become distorted nor is the general shape of the plant af-
fected. The flowers appear normal in color and fruits are generally nor-
mal although occasionally they may be stunted, misshapen or streaked.

Several diseases affect eggplant in South Texas which might be mis-
taken for this disease by one who has never seen yellows. Confusion
should not result if it is rememberd that in eggplant yellows the disease
starts in the young leaves and passes down the branch and that the color
is greenish-yellow at first, then orange-yellow and finally white.

The symptoms of eggplant yellows resemble those of potato calico as
described and illusirated in color by Porter (8). However, these di-
seases are probably not the same. ‘

EXPERIMENTAL PROCEDURE

These investigations were started in 1934 an.d continued through 1939.
All field studies, unless otherwise stated, were conducted on sandy loam
soil on Texas Substation No. 19, Winter Haven. The Florida High Bush
variety was used in 1934 and Black Beauty in all later tests. Seeds
were planted early in July in a bed and grown under part-shade until
the plants were about two weeks old. The seedlings were watered by
sprinkling at first and by flooding after emergence was complete. The
average period from time of planting seeds to transplanting to the field
was 40 days. The plants were set in the field about the middle of
August in rows four feet apart and plants two feet anart in the row.
The field was irrigated, fertilized and cultivated in the usual manner
followed by commercial growers" to produce good eggplant yields. The
field plots usually contained about 200 plants. Treatments were not
replicated, except in 1937. The plots were separated by four rows of
tomatoes during 1938 and 1939 to guard against dust drifting from one
plot to another.

The plants in the seedbed were dusted after each rain and sprinkling
irrigation, and at least once each week to keep them lightly covered with

8 BULLET'IN NO. 623*, TEXAS AGRICULTURAL EXPERHVIENT STATION

dust at all times. Dust was applied after transplanting early in the
morning with a rotary hand duster at the rate of .20 to 25 pounds per
acre per application.

The progressive increase of the disease throughout the season was
determined by attaching a dated tag to each plant when the symptoms
first appeared. In 1936 the yield of eggplants on an untreated check
plot, having 93.0 percent of the plants diseased by the end of the season,
was nearly one-third less than the yield 0n the dusted plot, and in most
cases the quality was not as good. Other than this, yield records were
not used to judge the value of the treatments.

RESULTS

Since it was suspected by the author that som-e insect vector might be
scattering the disease, some preliminary tests were conducted in 1934
to determine the value of an insecticide for controlling the disease.
About one-half of a small plot of Florida Highbush eggplants was dusted
several times during September and October. None of the plants ex-
hibited symptoms of eggplant yellows when dusting was begun. The
dusted plot remained free of the disease and produced an excellent crop
while the undusted plot had 71.1 p-erce-nt of the plants diseased by the
end of the season. Further experiments were designed to see if these
remarkable results could be repeated and to learn how the dust pre-
vented the disease.

Effect of Various D-usts

The following dusts were used in eggplant yellows control experiments
1934-39: (1) sulfur containing 2 to 3 percent conditioning agent and
ground so that 93 to 95 percent would pass through a 325-mesh screen,
(2) sulfur-cube containing 0.5 percent rotenone, (3) sulfur-pyrethrum
containing 0.075 percent pyrethrins, (5) fuller’s earth-cube containing
0.5 percent rotenone, and (6) hydrated lime. In these tests the plants
were kept lightly covered With dust while they were in the seedbed and
two or more applications‘ were made beginning when the plants were set
in the field (third section Table 1). Sulfur gave perfect control of the
disease in four plots containing a total of 857 plants as compared with
42.0 percent diseased plants in the check plots. Only 1 out of 1275
plants in six plots dusted with sulfur-cube was diseased whereas in the
corr-esponding untreated checks an average of 29.2 percent was diseased.
Sulfur-pyrethrum dust gave perfect control in one test; however only
5.7 percent of the plants in the check became infected. This dust also
gave perfect control of the disease in 1934 when it was not used in the
seedbed but four applications were made, beginning at the time the

' plants were set in the field. Fuller’s earth-cube was used on one plot

containing 189 plants in which 11 or 5.8 percent became infected, in
contrast to 44.0 percent infection ‘in the untreated check. Hydrated

CONTROL OF EGGPLANT YELLOWS ' 9

lime was used in the seedbed and 4 dust applications were made after
transplanting in one test involving 196 plants, of which 10 or 5.1 per-
cent became infected. The check plot containing 400 plants had 233
or 58.2 percent diseased. However, the hydrated lime caused stunting
of the plants and should not be used for that reason. It has been ob-
served that stunted plants are less susceptible to this disease than more
vigorous ones. '

Time of Application

Experiments to determine the most practical time to dust eggplants
were conducted as follows: (1) dust applications were made throughout
the time the plants were in the seedbed and no dust was applied after
transplanting, (2) the seedbed was not dusted but two- or more appli-
cations‘ were made at 7 or 10-day intervals beginning at transplanting,
and (3) dusting was done both in the se-edbed and at 7, 10 and 14-day
intervals after transplanting.

Dusting the plants while in the seedbed with no treatment after trans-
planting gave good practical control of the disease during 1937, 1938,
and 1939. Only 24 or 3.7 percent of the 655 plants receiving this treat-
ment were diseased as compared with an average of 37.2 percent infec-
tion in the untreated check plots. In no case was‘ more than 4.8 per-
cent of the dusted plants diseased (Table 1, section 1).

Plants which were not dusted while in the seedbed but were dusted
two or more times beginning when they were transplanted to the field
remained practically free of the disease. The corresponding untreated
check plots had. an average of 35.8 percent diseased plants. However,
very poor control was obtained during 1935 when dusting was not started
until two weeks" after the plants were set in the field and 1.1 percent
of the plants were already exhibiting symptoms of the disease (Table 1,
section 2);

Dusting the plants in the seedbed and two or more times after trans"-
planting with sulfur or mixtures containing sulfur gave almost perfect
control in 11 plots. Only 1 of the 2348 plants used in this treatment
became infected as compared with an average of 33.2 percent diseased
plants in the checks. In this experiment the plants were kept lightly
covered with dust from the time they came up until they were fruiting.
Since the rainfall is normally light during August and September the
dust which adheres well to hairy eggplants was seldom washed off the
plants (Table 1, section 3).

Other Treatments

Tests were conducted to determine if the disease could be controlled
by mixing dusting sulfur at the rate of 500 pounds per acre with the
soil both in the seedbed and in the field. The sulfur was‘ thoroughly
mixed with the soil in the seedbed before the seeds were planted and

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CONTROL OF EGGPLANT YELLOWS 11

was placed in a furrow under the row before the plants were set in the
field. N0 dust was ever applied on the plants. In two tests involving
422 plants, 47 or 11.1 percent took the disease as compared with an
average of 49.6 percent infection in the check plots. The plants in the
treated plots did not show bad effects from the soil application of sulfur
(Table 1, section 4).

Since it was suspected that some insect vector spreads eggplant yel-
lows, the following treatments were used during 1936 and 1938: (1)
plants were grown under an 18-mesh screen wir-e cage while in the seed-
bed to protect them from insects and were grown in the open and not
dusted after transplanting to the field, (2) the seedbed was screened
as above but the plants were dusted 6 times in 1938 and 17 times in
1936, beginning when they were set in the field (Table 1, sections 5
and 6). Plants for check plots were grown in an open seedbed and
were not dusted. Screening the seedbed and no treatment after trans-
planting resulted in 90 out of 293 or 30.7 p-ercent infection as compared
with 48.2 percent diseased plants in the checks. Screening the seedbed
plus dusting after transplanting resulted in only one out of 266 plants be-
coming diseased. Plants grown under the screen cage were slightly
spindling, but appeared normal shortly after transplanting to the field.
Dusting the plants in the field beginning as soon as they are transplanted
provides almost complete protection regardless of whether or not the
seedbed is screened.

TRANSMISSION OF EGGPLANT YELLOWS

Since a high percentage of the plants in a field may have eggplant
yellows, there must be some effective means of natural transmission.
While insects are frequently supsected of transmitting many virus dis-
eases, the species involved in some cases has not been determined. Pe-
culiar habits of some insect vectors, such as feeding at night and leaving
the plant during the day, migratory insects feeding for a brief period
and then moving to another host, and other unusual habits make it dif-
ficult to determine the natural means of transmission.

Insects

Insects’ found in the eggplant seedbed and field were collected and iden-
tified. Many of those collected were feeding on a foamy sap, which ex-
uded from wounds on the main stem near the bud. The cause of these
injuries is not known but they were common about the time the first
fruits began to set. Other insects appeared to be attracted to irrigated
eggplant fields when the surrounding vegetation was dry. The follow-
ing number of species was‘ found in each insect order: Orthoptera 2,
Neuroptera 2, Thysanoptera 1, Homoptera 14, Hemiptera 25, Coleoptera
24, Lepidoptera 3, Diptera 20, and Hymenoptera 15. Of the 106 species
collected on eggplants, only a few are destructive and seldom are control

12 BULLETIN NO. 623, TEXAS AGRICULTURAL EXPERIMENT STATION

measures necessary. The following are pests at times in the Winter
Garden: white flies, blister beetles, fiea beetles and eggplant tortoise
beetles. Collections were made in the field experimental plots by sweep-
ing with an insect net to determine if there was any correlation between
the abundance of any species and the amount of yellows in the plot. The
common insects were uniformly present in all plots regardless of treat-
ment and this did not lead to the suspicion of any species as being the
vector. This sort of evidence was used to partially eliminate several of
the most abundant species from the list of suspected vectors. Aphids
have not been found on eggplants in the Winter Garden under field con-
ditions‘. However, they are sometimes common on eggplants grown in a
greenhouse during the spring months". This group contains more vectors
of virus diseases than any other and was therefore carefully studied.

Transmission tests were conducted by collecting insects in an eggplant
field and placing them on an infected eggplant for a few days and then
transferring them to a caged healthy plant where they were left for
a week or longer. The following species were tested in that manner:
Gratiana pallidula (Boh.), Psallus seriatus Renter, Euryopthalmus succinc-
tus (Linn.), Thyanta custator (Fabr.), Empoasca fabae Harris, Gargaphia
solaml Heidemann, Trialeurodes abutilonea (Hald.), and Thrips tabaci
Lindeman. None of these insects transmitted the disease from infected
to healthy plants. Several tests were conducted in which mass collec-
tions were taken from a field wher-e a high percentage of plants was in-
fected and placed on caged healthy plants. In one test a plant took the
disease, but the symptoms did not appear until more than two months
after the insects were placed in the cage. Two other plants in this cage
remained healthy. So far no ins-ect species has been proved to be the
vector of eggplant yellows.

Artificial Inoculation

Studies on artificial inoculation have been conducted by Dr. S. S.
Ivanoff (2), Plant Pathologist, Texas Agricultural Experiment Station,
Substation No. 19, who reports the following:

“This dis-ease, locally known as ‘eggplant yellows’ and resembling in
symptoms the calico type of virus disease was transmitted to healthy
plants of the variety Black Beauty by inoculation with extracted plant
juice, both by rubbing and by puncturing. There were more than l0
inoculation trials made in the seedbed and in the field during various
seasons in which approximately 1000 plants were employed. Infection
resulting from inoculation varied from 0 to 12 percent, with the control
of uninoculated plants remaining healthy after the usual incubation
periodn The degree of infection apparently depended upon the condi-
tion of the plants, upon the dilution of the infectious juice and perhaps
upon other factors not well understood. Ordinarily the disease was not
transmitted or transmission was very low when the inoculated plants
were stunted or were growing abnormally because of unfavorable en-

CONTROL OF EGGPLANT YELLOWS l3

vironmental conditions". The highest infection by artificial inoculation
was produced when the plants were young and growing vigorously.
Natural infection is much more common during the fall growing season
than during the early spring season.

“The incubation period varied from 14 to 24 days, apparently depend-
ing upon season and temperature. In spring most of the infected plants
had an incubation period of 18 to 21 days.

“Infection was produced regardless of whether the inoculated plants
were treated previously with sulphur or not. In one case young plants
were dusted 4 times previous to inoculation and2 or more times after
inoculation. Eleven percent of the inoculated plants became infected
while the plants which were likewise dusted but not inoculated, remained
healthy. Infection was also induced in plants in which, previous to in-
oculation, a few drops" of a 2 percent suspension of colloidal sulphur
were injected. It seems that the presence of sulphur within the Plant or
as dust upon the plant does not significantly prevent artificial infection.

“Extracted plant juice from diseased plants, slightly diluted with
water, was passed through a Seitz filter and then used to inoculate healthy
plants but, in the few trials made, no positive case of infection occurred.
S-eed obtained from diseased plants produced only healthy plants.

“Attempts to isolate a causal microorganism on common culture media,
from diseased leaf, petiole, and stem tissue, under aseptic conditions,
have so far been unsuccessful. It app-ears that this disease is an infecti-
ous one and caused by a virus.” Following recent inoculation (3) it ap-
pears that the disease is closely related to cucumber mosaic.

Grafts

Transmission studies were conducted during 1938 in Which buds from
a plant showing symptoms‘ of eggplant yellows were grafted onto ap-
parently healthy plants. The grafts were made on plants which had
previously been dusted with a sulfur-cube mixture while in the seedbed
and four times at 10-day intervals after they were set in the field. The
grafted buds liv-ed on 12 plants and the disease was transmitted in every
case. The symptoms appeared after an average period of 31 days. The
remaining 207 plants in the plot which were also dusted but not grafted
did not take th-e disease. In a number of instances where the grafted
buds failed to live, the plants remained healthy even though the diseased
buds were in contact with the cut surface of the healthy plants for a
week or longer. These results confirm those of Taubenhaus" and prove
the infectious nature of the disease. The continuous presence of a sul-
fur-cube dust on plants prior_to the time the graftings were made did
not prevent transmission of the disease.

Tomato buds were grafted on infected eggplants and infected eggplant
buds on tomatoes. Although the grafted buds lived, the tomato plants
did not develop symptoms of eggplant yellows. Eggplant is the only
plant known at present which exhibits symptoms of this disease.

14 BULLETIN NO. 623, TEXAS AGRICULTURAL EXPERIMENT STATION

DISCUSSION

It is not und-erstood how the various treatments used in these experi-
ments acted in controlling eggplant yellows. While sulfur or mixtures
containing sulfur both as a dust and soil amendment were specific in
controlling the disease, dust applications of fuller’s earth-cube and hy-
drated lime were also effective. It seems doubtful that the disease con-
trol obtained by all of these treatments can be satisfactorily explained
with the information at hand on the basis of insect vector control alone.
If some insect is involved it must be easily killed or repelled by all of
these materials. It is thought that the hydrated lime dust controlled
the disease by stunting the plants, as already pointed out, since it is not
known to be of much insecticidal value. The author has no explanation
to offer as to how the soil treatment with sulfur acted in controlling the
disease, and suggests that further work is needed along this line. While
screening the seedbed to protect the plants from insects gave some con-
trol of the disease, this method was not as effective as dusting the seed-
bed only; it should be pointed out that the screened plants grew some-
what spindling due to the part-shade and it is thought that this ab-
normal growth might have influenced the greater amount of infection
taking place. Although an insect vector of eggplant yellows has not been
found, this possibility has by no means been exhausted.

The time infection takes place has" not been definitely determined but
according to the second and last sections of Table 1 it takes place with
few exceptions in the field after transplanting. However, very little con-
trol was obtained when treatments were started after infection has al-
ready occurred, as in 1935 when dusting was begun two weeks after the
plants were set in the field. Since the disease increased most rapidly
during October, or 6 to 10 weeks after the plants are set in the field, it
appears that infection, based on the length of the incubation period fol-
lowing artificial inoculation, must largely take place after transplanting.
If that is true, the dust which was applied in the seedbed thereby pro-
viding very economical protection probably adhered to or affected the
plants for a considerable period of time and prevented infection taking
place later.

It is not understood why eggplants grown in the spring or early sum-
mer months are largely free of the disease while those grown later in
the year in the same area are so badly affected. Diseased plants which
live through the winter continue to exhibit typical symptoms in the
spring, for the disease is readily transmitted through grafting during the
spring months.

CONTROL RECOMMENDATIONS

The cheapest and most practical control of eggplant yellows was ob-
tained by dusting the plants in the seedbed with sulfur. The dust may
be applied with a small hand duster or shaken from a cloth sack. About

CONTROL o-F- EGGPLANT" YELLOWS 15

ten pounds of dusting sulfur should be enough to use on a s'eedbed of
sufficient size to plant one acre of eggplants. The plants should be kept
covered with the dust from the time they come up until they are trans-
planted to the field. As an additional precaution, the plants should be
dusted at the time they are pulled for transplanting to the field. The
sack or dust gun used should be kept in a convenient place so that the
seedbed can be dusted after every rain and at least once every Week to
keep the growth covered with sulfur. The additional control ob-

Figure 2. - '.I.‘wo plots of eggplants on November 16, 1939, which were separated by
four rows of tomatoes. Top picture of untreated check had 58.2 per
cent of the plants diseased. The bottom picture shows plot which had
plants dusted with sulfur while in seedbed and not dusted after the
plants were set in the field. Only 3.5 per cent of these Plants were
diseased.

16 BULLETIN NO. 623, TEXAS AGRICULTURAL EXPERIMENT‘ STATION

tained by making dust applications after the plants are set in the field
has" not been found profitable.

The important point to remember is that dusting should be done be-
fore the disease appears since no method is known which will restore
health to the infected plants.

SUMMARY

Eggplant yellows occurs during the late summer and fall months in
South and Central Texas, and what is said to be the same disease was
reported in Oklahoma, Louisiana, Florida, and South Carolina. It is
infectious and appears to be caused by a virus. Conspicuous yellow spots
which first appear in the young leaves increase rapidly in size, frequently
following the veins, until all the green chlorophyll is" destroyed, in about
25 days. The disease first appears when the plants are 8 to 10 Weeks
old and increases rapidly after that time. The contrast of y-ellow and
green in an eggplant field is apparent at considerable distance, especially
about harvest time wh-en most of the plants may be diseased. The re-
duction in yield depends upon the percentage of plants diseased and their
age when infection occurs.

The method of normal transmission is unknown. It does not appear
to be readily transmitted under natural conditions during cultivation,
irrigation or harvesting. Infection resulted after 31 days when dis-
eased buds were grafted on healthy plants. While insects are suspected
of transmitting the disease, definite proof is lacking.

Control studies involving 9,092 plants on 54 field plots were con-
ducted at Texas‘ Substation No. 19, Winter Haven, during the period
1934-39. The plants were grown under natural conditions, following
the practices used by progressive eggplant growers.

It was found that sulfur, sulfur-pyrethrum, sulfur-cube, fuller’s earth-
cube and hydrated lime dusts were all effective in controlling the disease
when applied before infection took place, but the most economical re-
sults‘ Were obtained by the use of straight dusting sulfur.

Practical control was obtained when the plants were kept lightly cov-
ered with dusts containing sulfur throughout the time they were in the
seedbed and no treatment after transplanting. Slightly better control
of the disease was obtained by making four or more dust applications
at 7 or 10-day intervals, beginning at the time of transplanting to the
field. Practically perfect results were obtained when the plants were
dusted both in the seedbed and after transplanting to the field. The re-
sults were unsatisfactory when dusting was begun after infection had al-
ready taken place and a few of the plants were exhibiting symptoms of
the disease. No method‘ has been found for restoring health to diseased
plants.

Soil applications of sulfur at the rate of 500 pounds per acre, both in
the seedbed and in the field, resulted in 10.0 percent infection as com-

pared with 49.6 percent in th-e checks:
the disease is not due to a soil deficiency of sulfur.

CONTROL OF EGG-PLANT YELLOWS 17

Indications are, however, that
Plants in the seed-

bed grown under a screen wire cage for protection against insects had
about one-half as much infection as the checks.

The most economical control found consists of keeping the seedbed

cov-ered lightly with sulfur dust. This treatment is inexpensive and
easy to apply.

10.

11.

12.

LITERATURE CITED

Hawthorn, L. R. and J. J. Taubenhaus. 1934. Eggplant yellows. Texas

Agr. Exp. Sta. Rpt. for 1934:266-267.
1939. Texas Agr. Exp. Sta. Rpt. for 1939:

Ivanoff, Eggplant yellows.
g a

. S.
2 _-283. _
Ivanoff, S. S. 1942. The nature of eggplant yellows. Phytopath, 32:10-11.

Janes, M. J. 1937.
for 1937:3051’.

Jones. S. E. 1938. Eggplant Yellows. Texas Agr. Exp. Sta. Rpt. for 1938:
262.

Eggplant yellows control. Texas Agr. Exp. Sta. Rpt.

Jones. S E. 1939.

284-285.

Jones, S. E. and M. J. Janes.
Sta. Rpt. for 1936:326.

Porter, D. R. 1931. The infectious nature of potato calico.
6(9):277-294, 6 figs. and color plate.

Randolph, T. B. 1938.
Rpt. for 1938:7244.

1935.

Eggplant yellows. Texas Agr. Exp. Sta. Rpt. for 1939:

1936. Eggplant yellows. Texas Agr. Exp.

Hilgardia

Control of eggplant yellows. Texas Agr. Exp. Sta.

Taubenhaus, J. J. Chlorosis of eggplant. Texas Agr. Exp. Sta. Rpt.

for 19351102.

Taubenhaus, J. J. and L. R; Hawthorn. 1933.
Texas Agr. Exp. Sta. Rpt. for 1933290-91.

Tauben/haus, J. J. and L. R. Hawthorn. 1934.
Texas Agr. Exp. Sta. Rpt. for l93-4z92.

Chlorosis of eggplants.

Control of eggplant yellows.