MS University of California— College of Agriculture, AGRICULTURAL EXPERIMENT STATION. E. W. HILGAHD, Director. THE PHYLLOXERA OF THE VINE. By FREDERIC T. BIOLETTL VITIS VULPINA (Riparia), Typical wild vine from North America, (Resistant.) VITIS VINIFERA, Wild vine from the Caucasus. (Non-resistant.) A. J. JOHNSTON, BULLETIN No. 131. (Berkeley, Mav, 1901.) ;TY OF C/ LIBRARY COLLEGE OF AGRICULTURE DAVIS SACRAMENTO: : : : superintendent state printing. 1901. AVAILABLE PUBLICATIONS ON VINE AND OLIVE GROWING. The following 'publications will be sent free on application: Resistant Vines: Appendix to Viticultural Report for 1896. Bui. 116: The California Vine-Hopper. Bui. 119: Vine Pruning. Bui. 120: The Olive Knot. Bui. 123: Olives — Cultivation, Oil-Making, Pickling, Varieties. Bui. 127: Bench-Grafting Resistant Vines. Bui. 129: Condition of Olive Culture in California. Bui. 130: Preservation of Unfermented Grape-Must. Viticultural Report for 1887-95. (Contains on page 454 a list of the publications of the State Board of Viticulture, which will be sent on receipt of necessary postage.) Agricultural Report for 1895-96, 1896-97, containing: California Olives. Wine, Table, and Raisin Grapes at the substations. Agricultural Report for 1897-98, containing: Notes on the California Vine-Hopper. Revision of Bulletin 119: Vine Pruning. THE PHYLLOXERA OF THE VINE. The late discovery of the phylloxera of the vine in several important grape-growing districts which have hitherto been regarded as exempt has awakened widespread interest, and even alarm, among both wine- and raisin-producers. In order to satisfy the demand for information regarding this serious enemy of the vine, to allay the alarm of those who exaggerate its menace to the industry, and at the same time to rouse up to prompt and intelligent action those who are inclined to minimize the danger, the following brief account is issued. Historical. — The phylloxera is a native of the United States east of the Rocky Mountains, where it is found living upon the wild vines. It is a minute insect related to the scale insects and plant lice. It was introduced into the south of France before 1863, upon rooted vines sent from America; though the insect itself was not found and described there until 1868. The infection commenced at two points: one in the southeast in^Gard, the other in the southwest near Bordeaux. In 1868, when the nature of the pest was understood, it had already invaded considerable areas. The two areas first attacked gradually enlarged until they touched about the year 1880, and the insect began to spread northward. By 1884 about 2,500,000 acres, more than one third of all the vineyards of France, had been destroyed and nearly all the rest were more or less affected. The progress of the disease in parts of southern France was so rapid that in some towns vine stumps became the principal fuel. Since 1884 the pest has continued to spread with somewhat less rapidity in France, partly because the most densely planted vineyard districts had already been devastated, but also because elsewhere its progress was retarded by quarantine and other restrictive measures. No remedies yet discovered, however, are capable of exter- minating the pest; and to-day there is, no vine-growing region of any importance in France, or elsewhere, exempt from phylloxera. The insect was probably introduced into California upon vines — cut- tings or roots — imported from France, though it was possibly introduced from several sources and at several points. It was first noticed in the 62351 southern part of Sonoma County in the valley surrounding the old town of Sonoma, about 1874. By 1880 vines killed by the insect had been found in Napa, Solano, and Placer counties, and hundreds of acres had been pulled up in Sonoma Valley. Since then the insect has spread to all the important grape-growing regions of California north of Tehachapi,* and probably not less than 30,000 acres have been destroyed. The Insect.— The phylloxera occurs normally in four forms, which have been called by Victor Mayet: 1. The gall insect, or form of multiplication; 2. The root insect, or form of devastation ; 3. The winged insect, or form of colonization ; 4. The sexual insect, or form of regeneration. The gall insect lives upon the leaves, and is the commonest form on the wild vines in the native habitat of the insect. It rarely occurs in California. In Europe it is found often upon American and rarely upon European varieties. It causes little swellings or galls upon the leaves and younger parts of the vine, which, though sometimes very numerous, do little permanent injury. The chief danger from the gall form is that it multiplies with astonishing rapidity and migrates from the leaves to the soil. Here it attacks the roots and gives rise to the root form, which is the " form of devastation," the one which finally destroys all the vines it attacks which are "non-resistant." Every insect of the root form which reaches maturity lays about twenty-five or thirty eggs, each of which is capable of developing into a new egg-layer needing no fertiliza- tion. As there are from five to seven such generations during the year, the increase in numbers is extremely rapid. Sometimes during the summer, usually in July or August, some of the eggs laid by the root insects develop into insects of slightly different form, called nymphs. They are somewhat larger than the normal root form' and show slight protuberances on the sides, which finally develop into wings. These are the winged or colonizing insects, which emerge from the soil and, though possessing very weak powers of flight, are capable of sailing a short distance, and if a wind is blowing may be taken many rods or even miles. Those which reach a vine crawl to the under side of a leaf and deposit from three to six eggs. These eggs are of two sizes, the smaller of which produce males and the larger females. The female, after fertilization, migrates to the rough bark of the two-year- old wood, where she deposits a single egg, called the winter egg, which remains upon the vine until the following spring. The insect which hatches from this egg in the spring goes either to the young leaves and becomes a gall-maker, or descends to the roots and gives rise to a new generation of egg-laying root-feeders. The normal and complete life ~^The phylloxera is said to have been found once in Southern California; but as the vineyard was uprooted and destroyed the insect was probably extirpated. cycle of the phylloxera appears then to be as follows : Male and female insects (1 generation in autumn); gall insects (1-5 generations while the vines are in leaf); root insects (an unknown number of generations throughout the year); nymphs, which become winged insects (1 genera- tion in midsummer). The gall stage may be omitted, as it generally is in California, and the insects which hatch from the fertilized eggs laid by the female go directly to the root and produce offspring, which are indistinguishable from the root form produced in the normal cycle. For how many generations the root form can exist and reproduce with- out the invigoration supposed to come from the production of the sexual form is not known, but certainly for four years and probably for more. The gall form on American vines can be prevented by spraying the vines in winter with liquids to kill the winter eggs; but this treatment has no effect on the root forms, which in California hibernate abundantly in the soil. All forms of the phylloxera are extremely minute, the root form being about one twenty-fifth of an inch long when it reaches the adult egg- laying stage, and little more than half this length when young and active. It is just large enough to be seen by the unaided eye in a good light when its appearance is known, and, by the help of a glass magni- fying five diameters, its legs and antennae are plainly visible. Its color is light greenish-yellow in summer, and somewhat darker in winter; so that when numerous the attacked roots appear as though dusted in spots with powdered mustard or cinnamon. The newly-hatched insect is fairly active, and at first moves about from place to place on the roots; but finally, when it reaches the egg-laying stage, inserts its sucking-tube into the root and remains fixed. Nature of Injury. — The amount of nutriment taken from the vine by such minute insects, even when present in the immense numbers in which they sometimes occur, is not sufficient to account for the disas- trous effect upon the plant. The death of the vine is due to the decay which sets in wherever the phylloxera has attacked the roots. Where- ever a phylloxera inserts its sucking-tube a swelling is produced, com- posed of soft tissue which soon decays. When this swelling occurs at the end of a young rootlet, growth in length is stopped; when it occurs on the larger roots, a kind of "cancer" or decay spot is finally formed, which soon extends around the root, and all below the point of attack dies. During the first year or two after a vine is attacked there is little apparent damage. In fact, the effect of the phylloxera is equivalent to root-pruning, and in some cases results in an unusually large crop of grapes. The year after this crop, however, the vine having endured the double strain of heavy bearing and root injury is unable to recuperate, Fig. 1. Young roots of vine attacked by Phylloxera. S— Nodosities or swellings caused by the insect. B— One of these nodosities enlarged, showing position of the insects (P) and one-sided character of the swelling. Fig. 2. Galls or swellings caused by Nematode worms, which occasionally occur on vine roots in wet soils. Note their symmetrical axial character, which distinguishes them from Phylloxera nodosities. M— Eggs of the nematodes found in these galls. and generally dies. sudden, and two or even three small symptoms of the disease are evident. In rich, moist soil the death of the vine is not so crops may be obtained after Methods of Dispersal. — The ways in which new vines and vineyards become infested may be classed as natural and artificial. The natural ways may be inferred from what has been said of the life history of the insect. From a vine first attacked the root form spreads through the soil to neighboring vines slowly, but continuously, thus forming the so- called " oil-spots. " A typical oil-spot of several years' standing will show several dead vines in the center, then a ring of vines with very short growth and no grapes, next another ring where the growth is not of normal vigor, but where the crop may be equal to or larger than that of the healthy vines. Such a spot enlarges its area year after year at a gradually accelerating rate as the front of the invading army becomes longer. The rate of advance will vary with the soil and climate, but will probably never exceed forty or fifty feet annually. If this were its only method of spreading, the insect could be controlled or even exterminated with comparative ease. Unfortunately, it is able to spread much more rapidly by means of the winged form; and the rapidity of its extension over the south of France was due principally to this agency. In California, though the winged form has been found, — 7 — it seems to be rare, which probably accounts to some extent for the comparative slowness with which new districts have become infested. The artificial methods of dispersal are here probably more effectual in spreading the insect than the natural. The insects are taken from one part of the vineyard to another on pieces of the roots of infested vines, adhering to the plows or other implements used in cultivation; while they are introduced into new localities on rooted vines or cuttings brought from infested districts. METHODS OF COMBATING THE PEST. The methods to be used in resisting this foe of the vineyardist may be divided into groups corresponding to different stages of infection and to varying local conditions. There are three cases to be distinguished, viz: 1. The district is uninfested; 2. A few small infested spots are known in the district; 3. The district is badly infested; i. e., shows many and widely dis- tributed infested spots, even though none of the spots is large. 1. In the first case, all efforts should be* directed to keeping out the pest, and the only effectual means is a rigidly enforced embargo on all material capable of introducing it. Wherever the vineyard interest is of sufficient importance this should extend to the exclusion from infested districts, not only of all vine roots and cuttings, but also of all other plants, such as nursery stock, potatoes, etc., which are taken from below the ground. Although the phylloxera, so far as known, feeds on nothing but the vine, there is always danger of eggs or insects being contained in the earth attached to any kind of root. This measure, consistently carried out, has kept the province of Algiers free from infection, though the neighboring province of Constantine has been a prey to the pest for many years. 2. In the second case, where the insect has already obtained a foot- hold, the first step to take is to determine as nearly as possible the exact extent of the infested area. If it is found to be confined to a small, isolated vineyard, an effort should be made to completely eradi- cate the pest. This can be done only by destroying the vineyard, by subjecting it to what is called the "death treatment." This is best done (after grubbing up the vines and burning them on the ground) by making an embankment around the whole vineyard and then running water on to it until it is converted into a lake. The water should be kept continuously at a depth of at least six inches until all the insects are destroyed. The best time to do this is in May or June, as at that time four weeks' continuous flooding is sufficient to kill both insects and roots. It is important that every root should be killed in order that, if any insect survives the flooding, it will die for lack of food. Where — 8 — flooding is impracticable, the vines should be grubbed out and burned in the same way, and the ground kept clean of all growth for at least one year. This is in order that any suckers which may come up from the roots may be destroyed immediately. If crops, or even weeds, are allowed to grow, some of these suckers may escape observation and serve to keep the insects alive to spread the pest the next year. If the affected spot is not too large it is well to disinfect the soil with bisulfid of carbon. This is applied by pouring one ounce each into holes placed two feet apart all over the land to be treated. These holes should be about one foot deep and can be made with a small crowbar or dibble. After pouring in the liquid, the hole should be closed by pressing earth into it with the foot. If, however, the pest has obtained a foothold in several vineyards of the district, or in a large vineyard, it is practically hopeless to attempt to eradicate it. In this case all we can reasonably hope to do is to delay the spread of the pest as much as possible and in the meantime to place all new vineyards on a permanently phylloxera-resistant basis. Every infested spot in the district should be diligently sought out and treated. The treatment consists in digging up and burning every vine in each spot which shows symptoms of attack, together with at least three rows of apparently healthy vines surrounding them. Disinfection of the soil of these spots by flooding or with bisulfid of carbon is then advisable wherever practicable, but in any case these spots should be strictly isolated in all farming operations. In cultivating the healthy parts of the vineyard, to pass through the infested spots with plows or hoes is a most effective method of accelerating the spread of the insect. The search for infested spots is most easily and thoroughly done in July or August, as at that time the shortness of growth in the " oil-spots" is most readily detected and the insects are easily found, as they are in large numbers on the surface roots and generally also on the trunk of the vine just below the surface of the soil. The search for and destruc- tion of infested spots should be repeated every year; and if commenced in the early stages of infection and prosecuted with sufficient thorough- ness in every vineyard throughout a district, will effectually prolong the life of the bulk of the vines for many years. As soon as the actual presence of the phylloxera in a district is known and all hopes of per- manently eradicating it are abandoned, the embargo should be modified to the extent of admitting vine cuttings. These should be introduced, however, under strict quarantine regulations, including disinfection by responsible and properly instructed persons. Rooted vines, or cuttings with pieces of old wood attached, should still be kept out, as they cannot be disinfected with any certainty. 3. However conscientiously and completely these measures are enforced, a time will arrive sooner or later when the cost of inspection — 9 — and eradication will be greater than any benefit to be derived from them. We are then face to face with the third set of conditions; we must accept the phylloxera as a permanent inhabitant of the district and simply consider the best method of growing our vines in spite of its presence. By this time all embargo or quarantine regulations are use- less and should be repealed. Of the many thoue&nds of methods proposed and tested for maintain- ing a vineyard in spite of the phylloxera but very few have been of the slightest practical value and only four are at present used to any important extent. These methods are: 1. Injection of carbon bisulfid; 2. Flooding or submersion; 3. Planting in sand; 4. Planting resistant vines. The first two methods aim at destroying the insect ; the last two, at rendering the vines immune to their attack. As neither of the insecti- cidal methods can be applied with sufficient thoroughness to completely eradicate the pest without also killing the vines, the treatments have to be repeated every year in order to destroy the offspring of the few insects which escape the treatment of the previous year. For this reason these methods are being abandoned everywhere, especially in all new plantings, in favor of the others, which after the vineyard is properly started involve no further expense ; and as planting in sand is of very limited and local applicability, it may be said that at present the only method that need concern grape-growers in California very seriously is the use of resistant vines. This tendency to resort to resistant vines to the exclusion of all other methods is well illustrated by the following statistics of the vineyards of Herault, one of the chief grape-growing districts of France, and that in which the conditions most resemble those of California : Acres of Vines. 1880. 1890. 1899. 1. Treated with carbon bisulfid _ 6,600 3,900 6,200 15,000 9,900 311,000 800 2. Submerged 11,000 1,200 440,000 3. Planted in sand _ 4. Resistant vines 6,600 Bisulfid of carbon is a liquid which volatilizes very rapidly at ordi- nary temperatures and gives off a poisonous and highly inflammable vapor. This vapor is heavier than air and therefore gradually replaces and saturates the air in the interstices of the soil when the liquid is — 10 — injected. It is used at the rate of from 125 to 250 pounds per acre, and may be applied at any time except during blossoming and the ripening of the fruit. Two treatments, one directly after the vintage and the other a week or so before blossoming, give the best results. The liquid is applied by pouring from \ to f ounce into holes made from 18 inches to 2 feet apart all over the vineyard, care being taken not to put any nearer than 1 foot from a vine. The holes are made from 12 to 15 inches deep, and are closed immediately after pouring in the liquid by pressing the soil with the foot. The holes may be made with an iron rod or dibble ; but where the method is employed on a large scale special injectors are used, which much facilitate the work. The injec- tions are best made when the soil is fairly firm, and when it is neither very wet nor very dry. This method succeeds only in rich, deep, loose soils, and cannot be used successfully in soil containing much clay, or on dry, rocky hillsides. It is most effective in sandy soils, where the nature of the soil is itself unfavorable to the insect. It is least success- ful in warmer locations, where the insect is most prolific and most harmful, and is used chiefly in the cooler locations where the phylloxera does least damage. Vines which are much weakened by the attacks of the insects cannot be successfully treated, and all treated vines require fertilization and most thorough cultivation. The annual cost for mate- rial alone would be from $15 to $25 per acre, at the present market price of carbon bisulfid. Submersion is a cheaper and more effective method of controlling phylloxera, but is necessarily applicable to but few locations, and even where most successful is gradually giving way to the more satisfactory use of resistant vines. Its chief use is to preserve vineyards which are already in bearing, and it may be of use temporarily in some locations in California. During submersion the vineyard must be covered con- tinuously with at least six inches of water, as the object is to drown the insects; that is, to kill them by depriving them of air. If the surface becomes exposed even for a brief interval air will be absorbed and the insects given a new lease of life. In very porous soils submersion is impracticable on account of the large amount of water required, and ineffective for the reason that the rapid passage of the water carries suf- ficient air into the soil to keep the insects alive. Submersion is most effective in destroying the insects when they are in their most active condition, that is, in summer. At this time, unfortunately, the vine is also most sensitive to injury. The most favorable time, then, for sub- mersion is as soon as the vines have ceased active growth and before the phylloxera have entered their hibernating or dormant condition. This in most parts of California will be some time in October. At this period the flooding need last but a week or ten days; a month later, two or three weeks; while during the remainder of the winter little good — 11 — results unless the submersion is prolonged for thirty-five or forty days, and indeed in some soils of the extreme south of France two months has been found necessary. As the insect is most susceptible in midsummer, it was at one time thought that a copious irrigation at that time suffi- cient to destroy most of the insects without injuring the vines could be effected. At present a flooding in July for not exceeding forty-eight hours is practiced in a few places, but only to supplement winter-flood- ing, or the injection of bisulfid. The insecticidal value of the short submersion which the vines will withstand at this time seems to be very slight. Its main value seems to be in promoting a vigorous growth of new rootlets to replace those that have been injured. Planting in Sand. — Though no thoroughly satisfactory explanation has been given, the fact is established that in certain very sandy soils vines are uninjured by phylloxera. All sandy soils are unfavorable to the increase of the insect, and vines planted in them die more slowly than in others; but for complete immunity the soil must contain at least 60 per cent of siliceous sand. The looser and more fine-grained the sand, the more resistance it offers to the insect. Calcareous sands, those containing notable quantities of clay, all those in fact which have a tendency to form in lumps or "cake," offer less resistance. EESISTANT VINES. The most satisfactory method of combating phylloxera is the use of resistant vines, because it is applicable to all conditions and is the most economical in the end. A resistant vine is one which is capable of keep- ing alive and growing even when phylloxera are living upon its roots. Its resistance depends on two facts: first, that the insects do not increase so rapidly on its roots; and second, that the swellings of diseased tissue caused by the punctures of the insects do not extend deeper than the bark of the rootlets and are sloughed off every year, leaving the roots as healthy as before. The wild vines of the Mississippi States have evolved in company with the phylloxera, and it is naturally among these that we find the most resistant forms. No vine is thoroughly resistant in the sense that phylloxera will not attack it at all; but on the most resistant the damage is so slight as to be imperceptible. The European vine (Vitis vinifera, L.)* is the most susceptible of all, and all the grapes cultivated in California, with a few unimportant excep- tions, belong to this species. Between these two extremes we find all degrees of resistance, which is expressed by a series of numbers ranging from 20, indicating the highest possible resistance, to 0, indicating the utmost susceptibility. The following table shows the resistance (accord- *See frontispiece. 12 — ing to Viala and Ravaz and other authorities) of some of the best known species and varieties: Comparative Resistance to Phylloxera. Species (Wild Vines). Cultivated Varieties and Hybrids. Vitis rotundifolia 19 Vitis vulpina (riparia) 18 Vitis rupestris . 18 Vitis Berlandieri _ 17 Vitis aestivalis 16 Vitis labrusca 5 Vitis Californica 4 Vitis vinifera Gloire de Montpellier (Riparia) 18 Riparia X Rupestris 3309 18 Rupestris Martin 18 Rupestris St. George .. 16 Riparia X Solonisl616 16 Solonis _._ 14 Lenoir 12 Isabella... 5 The degree of resistance necessary for the production of good crops varies with the character of the soil. The resistance expressed by the numbers 16 to 20 is sufficient for all soils. A resistance of 14 or 15 is sufficient in sandy and moist, rich soils, where the vine can readily replace the rootlets as fast as they are destroyed. Fairly successful vineyards have been established exceptionally with vines having a resistance of less than 14, but as the vines become old the lack of resistance is generally shown by a weakening of the vine and a falling off of the crop. Many vineyards in the south of France grafted on Lenoir which formerly bore well, have now to be doctored with injec- tions of bisulfid. For this reason it is advisable to reject all vines with a resistance of 13 or under, especially as vines with greater resistance can now be obtained for practically all conditions. Resistant vines are of two kinds: (a) those which are grown for the grapes they produce, and (b) those which are useful only as stocks on which to graft the non-resistant varieties. The former are called u direct producers " the latter, " resistant stocks." (a) Direct Producers. — When the phylloxera commenced to destroy the vineyards of Europe, the natural attempt was made to replace them with the varieties of vines which had proved successful in the United States, where the insect was endemic. These varieties, however, all proved unsatisfactory. Some, like the Concord and the Catawba, were insufficiently resistant, and although they could be grown where the severe cold of winter impeded the prolificness of the phylloxera, they quickly succumbed in the milder grape-growing sections of Europe.* Most of them were poor bearers compared with the prolific European vines, and finally the character of their fruit differed so widely from what Europeans were accustomed to that there was little sale for the fruit, and the wine could compete with only the very poorest quality of * In California, these and other Labrusca varieties and hybrids resist very little longer than Vinifera vines. — 13 — Vinifera wines, and brought a very inferior price. A few of the varieties introduced during that first period are still grown to a limited extent in France, chiefly the Othello and the Lenoir. They are being gradually abandoned, however, as their crops are unsatisfactory, and in many localities can be maintained only by the aid of injections of bisulfid. For some years the search for a suitable direct producer was almost abandoned by practical men, the use of resistant stocks having been so fully successful. Lately, however, renewed efforts have been made and several new direct producers are being advocated and planted to some extent. The merit of these new varieties, however, is chiefly their resistance to Peronospora and Black Rot. Phylloxera-resistance is con- sidered of much less importance by their most ardent advocates, and indeed the advice is given to graft some of the best of these direct pro- ducers upon phylloxera-resistant stock. The main importance of these facts to California grape-growers is that they hold out hopes of perma- nent prosperity for the wine-making industry here, where, owing to the dryness of the climate, there is no likelihood of trouble from these serious fungous diseases of the grape, which threaten to make the grow- ing of Vinifera varieties impossible in many parts of Europe. (b) Resistant Stocks. — Though high resistance to phylloxera is essential in a grafting stock, there are other characteristics equally necessary. The Rotundifolia ( Scupper nong) which has the highest resistance of any vine, is useless as a stock on account of the impossibility of grafting it with any Vinifera variety. This is due to a lack of affinity, which means a lack of similarity in structure and composition between the tissues of the stock and those of the scion. This lack, in extreme cases, results in an imperfect and temporary union, but when not excessive, only in a slight decrease of vigor. The affinity is not perfect between Vinifera varieties and any resistant stock, but in the case of Riparia and Rupestris is generally sufficient to insure permanence to the union, and the slight decrease of vigor consequent often results in an increase of fruitfulness. It is for this reason that certain varieties when grafted on resistant stocks, especially on Riparia, often bear larger crops than when grown on their own roots. Not all varieties of Vinifera have the same affinity for the same stock. For this reason it is desirable to be cautious about making new or untried grafting combinations on a large scale. Some varieties, such as Carignan, Petite Sirah, Clairette, and Cabernet Sauvignon do excellently on all stocks; while others, such as Mondeuse and Gamay do not make a very good union with any of the thoroughly resistant stocks. The Petit Bouschet and Cinsaut make very poor unions with any variety of Riparia, but do fairly well on Rupestris St. George. The Pinot Noir makes a vigorous growth upon Rupestris St. George but bears much more prolifically upon Riparia Gloire; while the Mataro — 14 — does not bear on Rupestris St. George and makes poor unions with Riparia Gloire.* Selection. — A very serious defect of many resistant stocks is a slender habit of growth. This is true of most of the vines found growing wild, and cuttings from such vines make poor grafting stock for the stout Vinifera varieties, which will produce a trunk four inches in diameter while the stock is growing only two inches. This is particularly true of the wild Riparias. For this reason great care has been exercised in selecting the stronger-growing forms, and at present we have selected Riparia-varieties which almost equal Vinifera in the stoutness of their trunks. The best of these are the Riparia Gloire de Montpellier and the Riparia Grande Glabre, the first of which has given the best results in California. Adaptation. — The European vine is remarkable among cultivated plants for the wide range of soils in which it will succeed. We find vineyards producing satisfactory crops on the lightest sands and on the heaviest clays, on the dry hill-tops and in the low, moist plains. This is not the case with resistant stocks. Some, such as the Rupestris varieties, are suited to the driest soils; others, like the Riparia varieties, grow well only on rich, moist soils. The question of the adaptation, then, of resistant stocks to various soils is of the greatest importance if we are to obtain the best results. After rejecting all unselected and unnamed varieties, such as the ordinary Rupestris and Riparia, which have caused so much disappoint- ment and loss on account of their poor growth, and all insufficiently resistant varieties, such as Lenoir, which have succeeded only in the richest soils, our choice of a resistant for a particular soil, climate, and scion must depend on its qualifications as regards affinity and adaptation. After testing hundreds, if not thousands, of varieties and hybrids originated in Europe and America, a few have been selected as the best for practical purposes. In France a fairly good resistant stock has been found for nearly every soil. In California little systematic work has been done in this respect, and we still have the intricate problems of adaptation to solve for most localities. We can, however, profit to some extent by the experience of Europe, and some of the best varieties . have been partially tested here and give great promise. For the driest soils, on hillsides with a southern exposure, the Rupestris Martin is the most promising variety. Though not quite such a vigorous grower as the St. George it has greater resistance to phylloxera, and where grafted has given equal if not superior results. Where the soil is somewhat compact the Rupestris St. George is to be preferred, but neither of them should be planted where, on account of *"Reconstitution du Vignoble," par P. Gervais, 1900. __ 15 — an impervious subsoil or a high water-table, deep penetration of the roots is impossible. For very shallow soils no resistant has been found that gives perfectly satisfactory results, but in such situations Riparia often does better than Rupestris. Where ground water is too near the surface Rupestris is liable to fungous root-rot. Near Mission San Jose there are vine- yards on rolling hills where the soil consists of a layer, from 2 to 4 feet thick, of the heaviest black adobe underlaid by a sandy subsoil. Here Riparia has grown more vigorously and produced better crops than Rupestris. The subsoil, though easily penetrated by vine roots and favorable to their growth in normal seasons, loses its water, which is taken up by the more hygroscopic surface clay in dry years. In such conditions the deep-rooted Rupestris suffers, while the Riparias, with all their roots in the adobe, remain vigorous. For loose, moist soils on northern slopes, and in those situations where a horizontal root development is desirable or permissible, the Riparia Gloire de Montpellier is extremely promising. It should be planted wherever Riparias of any kind have proved to do well, as in certain soils and locations in the San Francisco Bay region, and in the sub-irrigated soils of parts of the San Joaquin Valley. Other very promising resistants are certain hybrids of Rupestris and Riparia, which in many ways combine the merits of both species. Of these, Riparia X Rupestris 3309 and Riparia X Rupestris 101 14 have given the most favorable impression in California. They are strong, vigorous growers, with a greater range of adaptation than the pure species, and a resistance to phylloxera equal to that of Riparia Gloire. DISINFECTION OF CUTTINGS. The simplest and most effective method of treating cuttings suspected of being infected with phylloxera is to expose them to the fumes of bisulfld of carbon. The treatment with liquid insecticides is not nearly so reliable, as Professor Hilgard pointed out many years ago, on account of the difficulty of wetting the buds of many varieties, owing to their protective covering of woolly hairs. Some fear has been expressed that the poisonous fumes would injure the vitality of cuttings, but Professor Hilgard demonstrated in 1881 that Zinfandel cuttings kept for twelve hours in an atmosphere saturated with the fumes showed no signs of injury, and grew as well as untreated cuttings. Recent tests with resist- ant cuttings, Riparia and Rupestris, indicate that they can be treated with equal safety, for even after twenty-five hours' treatment they were not killed, though their slowness in starting and callusing indicated that they were injured. After five hours' treatment Rupestris St. George cuttings were uninjured and sent out roots and buds vigorously and rapidly. A large lot (about 4,000 cuttings) of Rupestris St. George, — 16 — Rupestris X Riparia 3309, Riparia Gloire, and Solonis were exposed in a saturated atmosphere of carbon bisulfid for seven hours, and at the present time they are rooting and show no signs of injury. As Professor Hilgard's experiments in 1881 showed that one half hour exposure was sufficient to destroy the summer eggs of the insect, the time latitude is quite sufficient for safety, even for the winter egg. The method of using the bisulfid is as follows: Place the cuttings in a barrel, vat, or box made tight by means of a thick coat of paint, or of paper pasted on the inside. On top of the cuttings place a saucer or other shallow dish, into which to pour the bisulfid of carbon. An ordinary saucer will hold enough for a box 3 feet cube or a 200-gallon vat. For larger receptacles it is better to use two or more saucers. Deeper vessels will not do, as the saturation is not sufficiently rapid. After pouring the bisulfid into the saucer, cover the box with an oiled canvas sheet or other tight-fitting cover, and allow to stand for from forty-five to ninety minutes. At the end of this time there should be a little of the bisulfid left. If it has all evaporated this is proof that insuffi- cient was used. No flame lights should be used, as the liquid burns easily and the fumes form an explosive mixture with the air. Care should be taken not to spill any of the liquid on the cuttings, as it may kill them. It is advisable to cut off about half an inch of the lower end of the treated cuttings before planting, as the vapor injures the open pith. Besides disinfecting the cuttings in this way, all the packing material in which they come should be burnt, or if valuable, dipped in boiling water. Practically it is impossible to disinfect rooted cuttings satis- factorily on account of the difficulty of killing all the phylloxera without seriously injuring the vine roots.