UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE _ AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA CIRCULAR 288 May, 1925 PHYLLOXERA RESISTANT VINEYARDS BY L. O. BONNET Nursery of bench grafts. INTRODUCTION The Phylloxera is the most widespread and destructive insect which attacks the vine. It exists in all the principal grape growing regions of the world, and in most of them has destroyed all or the greater part of the vines which grew there before its arrival. In California, it has found its way into all the large grape growing districts and has destroyed most of the original vineyards in the north- central coast counties. According to the State Department of Agri- culture, the following counties are free from Phylloxera : Alpine Mariposa San Bernardino Amador Merced Santa Barbara Del Norte Modoc Shasta Humboldt Mono Sierra Imperial Nevada Siskiyou Inyo Orange Stanislaus Kern Plumas Tehama Lake Eiverside Trinity Lassen San Benito Ventura Los Angeles Z UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION The Insect. — The insect is a native of the eastern United States, particularly of the Mississippi Valley, where it lives upon the native species of Vitis (''grape vines"). In its native home, it has several forms or stages. One, the gall form, lives on the leaves throughout the summer. Some of the gall insects migrate to the root where they live and multiply for an indefinite time. Some of these root insects, usually in late summer, produce a winged form which emerges from the ground and by flying, with the help of the wind, carries the pest into new vineyards. The winged form lays eggs upon the leaves of the vines it reaches and these eggs hatch into the fourth or sexual form. The female insect produced in this way lays the winter egg under the dry bark which protects it during the winter. In the spring when the leaves of the vine are formed, the winter egg hatches and the insect, finding its way to a leaf, gives rise to a new generation of gall insects. In California, only the root form occurs in most cases. The winged form appears occasionally in large numbers in a few districts but there seems reason to believe that it does not lay eggs or produce the sexual form. The gall form has never been found in California. The insect is related to the aphids or plant lice and, in all forms, is extremely small — just visible to the unaided eye — but large enough to be seen readily with an ordinary hand magnifying glass. Injury to the Vine. — The only serious injury done to the vine is due to the work of the root insect, which punctures the roots, forming ''nodosities" at the tips of the rootlets and "tuberosities" on the large roots. The tip galls stop the growth of the rootlets, and the decay of the swellings on the large roots destroys the bark and growing layers and finally causes the death of the whole root system. Degrees of Susceptihility. — Some species of vines are readily attacked by the insect and others are almost immune. The European species, Vitis vinifera, of which our Californian grapes are varieties, is the most susceptible of all. The American species, of which there are nearly twenty, possess resistance of varying degrees, from practically complete immunity to a susceptibility little less than that of V. vinifera. The degree of resistance of a vine is expressed by numbers from 0, representing the maximum susceptibility of Vinifera, to 20, repre- senting immunity or the theoretical maximum resistance of a vine which the Phylloxera cannot attack at all. The following list gives the relative resistance of the principal species which interest the grape grower : ClKC. 288] PHYLLOXERA RESISTANT VINEYARDS Phylloxera Eesistance of Species of Vitis Species — Origin Resistance 1. V. rotundifolia American 19 2. v. vulpina (riparia) American 18 3. v. rupestris American 18 4. V. cordifolia American 18 5. V. berlandieri American 17 6. V. aestivalis American 16 7. V. lincecumii American 14 8. V. labrusca American 3-5 9. V. californica American 4 10. V. vinifera European 0-1 All the American species have a high degree of resistance with the exception of Labrusca and Californica which are but little better than Vinifera in this respect. Hybrids of these species have degrees of resistance intermediate between those of the parents. Means of Defense. — The means of defense against the Phylloxera are: Prevention. — Quarantine against infested material and disinfec- tion of planting stock. This is very useful in delaying the spread of the insect, sometimes for many years, but it is seldom that it can be relied upon for permanent protection.* Cure. — There is no certain cure if the insect has obtained a foot- hold in the vineyard. Temporary relief can be obtained by ** sub- mersion," that is by keeping the vineyard covered with water to a depth of several inches continuously for from three to five weeks dur- ing the dormant season. It is very rare that this is practicable and, in any case, the insects are seldom all destroyed, and the flooding must be repeated every few years. The number of insects can also be reduced below the danger point by treating the soil with carbon bisulfid, but this is expensive and must also be repeated periodically. Applying paradichloro-benzine promises to be effective, but has not been thoroughly tested and is, moreover, also very expensive. In most cases there is no practical cure known for a vineyard infested with Phylloxera. Immimity. — There are two methods of permanent protection ; one of general applicability, and one possible under special conditions. The latter is based on the fact that vines of any kind are immune from attack if growing in extremely sandy soil, similar to the ''blow sands'' of some of our grape growing districts. A soil, to be com- pletely immune, must contain at least 60 per cent of silica sand. * See Circular 226, '* Protection of Vines from Phylloxera,** which can be obtained by applying to the College of Agriculture, Berkeley, California. 4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Smaller amounts afford temporary or partial protection, probably by interfering with the movements and spread of the insect. The only method of general applicability is the use of resistant vines. These can be used in two ways : (a) as direct bearers. This means the growing of vines of resistant varieties for fruit. Unfor- tunately, quality of fruit and resistance to Phylloxera are inversely proportional — the more resistant the variety, the poorer the fruit, the better the fruit of the variety, the lower the resistance. (&) As grafting stock. If we use a resistant vine as a root stock and graft on it a variety which produces the kind of fruit we require, we have a compound vine whose roots are safe from Phylloxera and whose crop is of the quality desired. The root has no unfavorable influence on the quality of the fruit and the top does not diminish the specific resistance of the root. The use of resistant root stocks, therefore, is the method used almost exclusively in most of the vineyard districts of the world as the means of protecting vineyards from Phylloxera. This circular is concerned with the practical application of this method for vineyards in California. EESISTANT EOOT STOCKS The selection of the stock is one of the most important parts of the problem, because on it depends the productiveness and the duration of the vineyard. When a stock has been well selected, that is to say, when it is adapted to the soil and climate, and also suited to the scion desired, success will follow if proper cultural methods are used, while a poor or bad selection will inevitably result in a partial or total failure. Varieties Suitable for California. — Resistant stocks are classified into three groups : American stocks, i.e., varieties of a pure American species; American x American stocks, i.e., crosses between two or more American species ; and Vinif era x American stocks, i.e., crosses between Vinifera and American species. Each of these groups contains many varieties, but some have been rejected for various reasons, after trial and experience, so that today, the problem of what stock to plant does not present the pitfalls it did some years ago. Experience in this matter is meager in California, however, even for the coast counties where more or less successful resistant vineyards have been established for twenty years, and new problems arise with the spread of the pest into vineyards growing under different soils and climatic conditions. After the experience of the past, here, and in other grape growing countries, few stocks are being used of the thousands that have been produced and tried. The following table gives the standard varieties CiRC. 288] PHYLLOXERA RESISTANT VINEYARDS 5 which have been found successful in California and also a few others which, though new, are very promising on account of the results they have given in France and Algeria under conditions similar to those of California. List of Resistant Stocks American — Riparia x Rupestris 101-14 Riparia Gloire Riparia x Berlandieri 420A Rupestris St. George *Berlandieri x Novo Mexicana 31R American x American — *Rupestris x Berlandieri 57R, 90 R, llOR Riparia x Rupestris 3309 Vinifera x American 1616, 1613 Riparia x Rupestris 3306 Chasselas x Berlandieri 41B The stocks contained in the above table are not suited to all soils nor to all climates ; in fact, the diversity of their original habitats and their characteristics are an indication of differences in adaptation. The following notes on these stocks are based on experiments carried out in California, on the works of Professor L. Ravaz, on an article entitled, ''Les Meilleurs Porte-Greff'es actuels, " by A. Bonnet and on published accounts of results obtained in other countries especially in Algeria. They should be consulted for the selection of the best stock for a given soil and climate. Riparia Gloire. — This is a stock for the rich, loose, moist bottom soils of the coast region, especially of the fog belt. This variety of Riparia ripens the fruit of its scions early and favors the production of large berries and well set bunches. • It roots and grafts easily. It is entirely unsuited to the interior regions of California and its use in the state is in consequence very limited. Rupestris St. George (Syn. R. du Lot). — This is the most interest- ing variety of its species and is grown more in California than any other stock. It grows with great vigor in deep soils, as long as the soils are not too compact or dry. Deep soil is necessary for its plung- ing root system. In shallow soils, dry or wet, it always fails. It thrives in the hot climate of the interior valleys. Rupestris St. George roots and grafts well, and, for these seasons, has been propagated in Cali- fornia almost to the exclusion of other stocks. But, its indiscriminate use has led in some soils and under certain climatic conditions to failures. This stock does not favor good setting of blossoms and, for this reason, should not be grafted with varieties subject to ''Shelling," ' ' Shot berries " or ' ' Coulure. ' ' In other words, it tends to diminish the productiveness of the scion. This tendency is less with some varieties and diminishes with age. It withstands white alkali to a certain degree. * The varieties marked with an asterisk are new hybrids and included simply as worthy of trial. b UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Riparia x Bupestris 3309. — A stock having the general adaptation of its parents. It utilizes soils of medium fertility better than Riparia Gloire and also those which contain more limestone than this stock can withstand. 3309 does not force vegetative growth so much as Rupestris St. George and promotes better setting of fruit. It has been used indifferently with 3306, but experience has shown 3309 the better suited to light, gravelly and loose soils. It roots and grafts well. These valuable characteristics explain the large use which has been made of this stock. It appears to be very sensitive to alkali and should not be planted in districts where much alkali is found. Riparia x Rupestris 3306. — This variety which is from the same cross is less planted than 3309. However, in California it has usually given as good results as 3309 and sometimes better. It does well in fairly compact soils, especially those which are liable to become very moist for sometime. In years of drought, it does better in those places than 3309. It should probably be given the preference over 3309 in the San Joaquin Valley. Riparia x Rupestris 101-14. — This hybrid has been little used in Europe where a pure Riparia which it resembles in adaptation, is pre- ferred. It shows the influence of the riparia parent more than the others. It does particularly well in rich, irrigated soils and is less sensitive to a hot climate than the pure riparias. It is promising for use in suitable mellow soil in the central valleys. It has been little used in California but deserves testing, especially for Muscat and table grapes. It is probably less widely adapted than 420A but it is more easily handled in the matter of rooting. Riparia x Berlandieri 420 A. — This is the most interesting variety of its class, and is almost the only one which has been tried in Cali- fornia. It possesses to a marked degree the qualities of the Riparia united with those of the Berlandieri. The Berlandieri is resistant to drought and grows well in compact soils, more or less shallow. It strongly favors the fertility of the scions it bears, and this character- istic is always transmitted to its hybrids. Unfortunately, when pure it does not root well. The hybrid 420A is adapted to rather compact soils which may become dry during the growing season. Its regularity in production and the quality of the grapes it produces are very notable. The percentage of successful bench grafts is low though the unions of those which grow are excellent. It has the reputation in France, common to other Berlandieri hybrids, of developing slowly at first. At Davis and Kearney, however, it has grown well. Grafting on rooted vines gives better results with this stock than bench grafting. CiRC. 288] PHYLLOXERA RESISTANT VINEYARDS 7 Berlandieri x Novo Mexicana 31R. — This stock is more vigorous than 420A, and very fruitful, but it has not yet been experimented with in California. Rupestris x Berlandieri 57R, 99R and llOR. — These three varieties, although rather new, seem superior to all of the old crosses of the same group. They promise to be useful here, for they have the vigor of the Rupestris combined with a certain degree of the fruitfulness of the Berlandieri. They are described as promoting good bearing and as resistant to drought. The latter characteristic is particularly interest- ing under Californian conditions. They are adapted to shallow as well as to deep soils, and withstand a high percentage of lime. These char- acteristics place this group of stocks above the group of Vinifera x Americans, and even of that of pure American stocks. They were introduced at the University Farm vineyards two years ago, and are being tested there. Solonis Hybrids, 1613, 1616. — The first, 1613, is a hybrid of Solonis and Othello (Solonis x Riparia-Labrusca- Vinifera) ; the second of Solonis and Riparia. The composition of the former indicates insuffi- cient resistance to Phylloxera. It has given good results in the vigor and bearing of its scions but it would be risky to plant it except per- haps in very rich, well irrigated soils. The second, 1616, is five-eighths Riparia, two-eighths Candicans, and one-eighth Rupestris. It is of sufficient resistance to Phylloxera and is adapted to good soils well supplied with water. A valuable characteristic is its tolerance for alkali in which it exceeds most resistant stocks. According to Mr. R. L. Nougaret 1613 is very slightly infested by nematodes, and 1616 is immune. This immunity of 1616 may be used with advantage in soils infested with that pest, for the culture of Vinifera varieties badly attacked by it. Chasselas x Berlandieri 41B. — A well known Vinifera x American hybrid which has withstood Phylloxera under practically all condi- tions, although suspected of insufficient resistance for a long time. Old vineyards grafted on this stock are still fertile and vigorous. It is considered only fairly vigorous in France and, like the 420A, to grow rather slowly for a few years after planting. In the experiment vine- yards at Davis and Kearney, however, the vines grafted on this stock have been among the most vigorous. Its special value lies in its great power of resistance to Chlorosis, although 41B can be grown in a variety of soils, with or almost without limestone. A disadvantage of this stock is that it is difficult to root. It gives a low percentage when bench grafted, but it can be easily field grafted. This variety is 8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION adapted to fairly compact soils liable to become dry. The fruitfulness of its grafts is well known. Suitable ComMnations of Stock and Scion. — After determining the stocks which seem most suitable for the soil, climate, and other condi- tions of the proposed vineyard, the suitability of the scion variety to the stock chosen should be considered. The most important points in which combinations differ are: (a) fruitfulness, (h) durability, (c) ease of grafting. Investigations at Davis and Kearney have given some information on these points for some of our most important varieties.* Yield and Quality. — As already noted in the preceding account of promising resistant varieties, certain stocks tend to promote fruitful- ness of the scion more than others. This varies, however, with the scion variety. The stock which promoted the highest average crop in our investigations, 420A, showed the most variation in this respect with different scions. Where the fruitfulness of a particular combina- tion is not known, it is safest to use a stock which shows a low degree of variability in this respect. Some stocks also tend to promote quality in the fruit. This is difficult to measure exactly but a comparison of the sugar contents is perhaps the best single standard of comparison. The average standing regarding crop and sugar contents of the varieties mentioned tested at Davis and Kearney are as follows : stock — Sugar Crop Crop x Sugar Berlandieri x Eiparia 420A 23.2 245 229 Chasselas x Berlandieri 41B 23.1 213 198 Eiparia x Eupestris 3309 23.6 212 202 Eiparia x Eupestris 3306 24.3 193 189 Eiparia X Eupestris 101-14 22.7 189 173 Eiparia gloire 24.7 166 165 Eupestris St. George 24.8 100 100 . The variability of each stock with different scion varieties is shown in fig. 1. Durability. — The length of life of a grafted vine depends very much on the perfection of the union. In the most favorable cases, it is probably equal to that of ungrafted vines under the same condi- tions. Where the suitability of stock and scion is defective, there may be imperfect unions, and these will result in short lived vines. The number of vines which die during the first five years after planting is a fair measure of the durability of the combination. The average per- centage of vines on each stock dying yearly during the first five years with all combinations tried is shown below. * See Bulletin 331, Phylloxera-Eesistant Stocks. CIRC. 288] PHYLLOXERA RESISTANT VINEYARDS Stock — Death Rate Riparia x Rupestris 3309 1.9 Berlandieri x Eiparia 420A 2.0 Chasselas x Berlandieri 41B 2.4 Riparia x Rupestris 3306 2.9 Riparia gloire 3.2 St. George 3.4 420j\ 41 B 3300 II 3306 ||R. Gloire 1202 St. Geor<§j& BL 245 - £f3 1 " CROP " 1 166 _ 160 100 k. t93 k 1 1 1 1 P 1 ^J ^ABIL.ITY ? f ^■■^^ ^^^^^£ ^^^mSO ■ -»•«• .■ - , 1 1 J5 J.5 ^ 30 u SA d/ Fig. 1. — Record of seven principal stocks with ten scions. The durability of a graft depends as much on the scion as on the stock. Some scion varieties make durable combinations with most stocks. Others are difficult to suit in this respect. The tests at Davis show the average standing of some of our principal varieties on all the stocks tested as follows : Scion — Death Rate Sultanina (Thompson) Palomino .7 Sultana 7 Petite Sirah 1.1 Emperor 1.4 Malaga 1.7 Muscat 3.4 Alicante Bouschet 6.4 Tokay 7.1 Except the last three, these are all very good records. The Muscat and Alicante Bouschet are well known for their instability when grafted. The cause of the lack of durability of the Tokaj^ at Davis may have some connection with its susceptibility to frost and black-knot. 10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Ease of Grafting. — There is considerable variation in the ease with which cuttings of various stock varieties can be made to unite with the scion. This is principally, however, a matter of rooting. If the cutting does not root, the graft dies. The Berlandieri varieties root with difficulty and it is usually necessary to root them first before grafting. For more details on this subject the reader is referred to Bulletin No. 331, of this Station. In the following table are given the three combinations for some of the principal varieties of raisin, table and wine grape, which have been found best at Davis and Kearney Park, most weight being given to the yield and durability. Resistant Stock Recommended Scion Variety — First Second Third Muscat of Alexandria 41B 420A 3306 Sultanina 3306 420A 3309 Black Corinth 41B 3306 Sultana 41B 420A 3306 Tokay 420A 3309 3306 Malaga 41B 420A 3306 Emperor 3306 3309 Cornichon 3309 3306 ' 41B Alicante Bouschet 3306 3309 420A Petite Sirah 3306 41B 420A Valdepenas 3306 3309 420A Gros Mansenc 41B 420A 3309 Lagrain 41B 3309 3306 The Rupestris St. George is not mentioned at all in this table. The reason is that it has given generally the poorest results with the seven- teen scion varieties tested comparatively on various stocks. Further- more, with the exception of 41B, none of the Vinifera x American stocks, that in some cases have given as good results as some pure American or some Americo x American hybrids, have been mentioned here for the reason of their doubtful resistance. All the combinations listed have given good results and a choice among them should be made on the basis of the adaptation of the stock to the particular soil. Production of Resistant Cuttings. — In order to establish a vine- yard on resistant roots, we must have cuttings of the resistant stock from which to produce the root and cuttings of the desired vinifera variety for scions from which to produce the top. The scion cuttings are exactly the same as those used for ordinary rootings of non- resistant vines and are made in the same way. The resistant cuttings are made in a similar way from mother vines of the required variety grown specially for this purpose. CiRC. 288] PHYLLOXERA RESISTANT VINEYARDS 11 The number of cuttings obtainable from resistant mother vines will vary with the variety, the soil, and the age of the vines. Tests made at Davis indicate that about 25 per cent of the weight of the wood produced can be used for No. 1 cuttings suitable for grafting, and about 15 per cent for No. 2 cuttings suitable for rooting. The remain- ing 60 per cent is waste. On the average vines, in average soil, the number of cuttings varied from 50 to 100 No. 1 grafting cuttings and from 60 to 120 rooting cuttings. PRODUCTION OF GRAFTED RESISTANT VINES There are two general methods of establishing a resistant vineyard. One consists in producing a grafted resistant vine in a nursery and then planting this complete vine in the vineyard and growing it in practically the same way as that used for ungrafted vines with some special precautions explained later. The other consists in planting the resistant vine (cutting or preferably rooting) directly in the vine- yard where it is to remain permanently, grafting it later. The first is the better way because it is cheaper in the end and because it gives a more uniform vineyard and consequently better yields. Each of these general methods has several modifications, the most useful of which are described in this circular. Grafted Vines Produced in the Nursery. — There are three methods of producing nursery grafted vines: (a) the scion cutting may be grafted on the resistant cutting and then rooted in the nursery and planted in the vineyard a year later; (5) the resistant cutting may be rooted one year in the nursery, dug up the following spring, grafted and returned to the nursery for a year and planted out the third year. Both these methods are known as '^ Bench Grafting"; (c) the resistant cutting may be rooted for one year in the nursery, grafted in place without removal the following spring and planted out in the vineyard the third spring. This is known as ' ' Nursery Grafting. ' ' The first method is the most rapid and economical and is usually to be preferred. The second is useful for varieties which root slowly or with difficulty and for the utilization of cuttings of resistant stocks which are too small for grafting as cuttings. The third method avoids the expense of digging and replanting the resistant rooting but pro- duces very large vines which are expensive to dig and handle. Bench Grafting. — For bench grafting, cuttings for both stock and scion should be carefully selected. They should be true to name, properly matured and well supplied with starch reserves. The last characteristic is very important, for neither union nor growth can be obtained without starch. The amount of this substance in the tissues 12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION is easily estimated by the iodine test, which consists in covering a slanting cut made on a cutting with a few drops of a solution contain- ing one gram of iodine in 100 cubic centimeters of alcohol 150 proof, or ordinary tincture of iodine diluted with water. The presence of starch is shown by a blue coloration and the darker the color the better the grafting wood. Stock cuttings must be as straight as possible (see fig. 2). Their length should vary with the climate and the moisture of the soil. For the coast region a 10- or 11-inch cutting is best, while for the sandy loam soils of the interior valleys, a 12- or 14-inch stock is to be preferred. rig. 2. — straight cuttings suitable for grafting. Variety — Aramon x Eupestris Ganzin No. 1. Bench grafting can be begun as early as January, and continued until the middle of April. Before grafting, the cuttings should be soaked in water for twenty-four hours, disbudded thoroughly, and graded according to size. After soaking, the cuttings should be cut to the length required and disbudded with a sharp knife or a small pair of pruning shears. The grading is best made with the metal slot-grader shown in fig. 3. The length of the slot, which is cut in a brass plate, is 7 inches, with a width of 14 an inch at one end, and 14 of an inch at the other. The ends of the slot are widened into circles I14 i^ich and I/2 inch wide, respectively. The plate is marked with guide lines which determine the number and size of the grades. Any desired number of grades and relation between the grades can be obtained by varying the position of the guide lines. A percentage difference between grades is the best and five or six grades are sufficient. CiRC. 288] PHYLLOXERA RESISTANT VINEYARDS 13 Size Size Size Size Size Size Distance Between Lines for 6, 5, 4 Grade Sizes Five Sizes Four Sizes Size 1—1.04 inch Size 1—1.32 inch Size 2 — 1.20 inch Size 2 — 1.57 inch Size 3—1.37 inch Size 4—1.58 inch Size 5 — 1.81 inch Six Sizes 1—0.86 inch 2 — 0.96 inch 3 — 1.08 inch 4—1.21 inch 5—1.36 inch 6—1.53 inch Size 3—1.88 inch Size 4—2.23 inch F Fig. 3. — Slot grader — side view and front view. Behind the slot, at three-fourths of an inch, a piece of iron as a stop to hold the cutting, helps in grading accurately. With this marking of the grader, six size grades of cuttings are made, each varying in the same ratio from the next. The cuttings which fail to enter the slot or pass completely through are discarded as too large or too small for grafting.* The scion cuttings are then prepared. They are usually one bud scions, cut at ^^4 of an inch above each bud and with 1% to 21/4 inches of internode below. They should be soaked for about 12 hours, and then graded, always with the bud, either up or down. At this stage, the stocks and scion cuttings are ready to be grafted. Two methods of grafting are used, according to the type of callus- ing adopted. When sand callusing is chosen, the ordinary whip graft is used, while in hot room callusing the short or modified whip graft is preferred. * A fuller description of the slot grader and method of construction are given in Bull. 180, Eesistant Vines, pp. 103-105. (Out of print.) 14 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION In the ordinary whip graft, practiced by means of a special grafting knife, the upper end of a cutting is cut at an angle of a little less than 30 degrees, which gives a slanting cut about 2% times as long as the diameter of the cutting. A thin tongue is then made by cutting a little across the grain from the first third of the cut down to the second third, so that the tongue extends the length of the middle third of the cut. A similar cut and tongue are made on the scion and then stock and scion are adjusted together. To facilitate this operation, the tongues are opened by drawing out the knife obliquely. The graft A B Fig. 4. — A. Modified whip graft. B. Ordinary whip graft. is then tied with raffia or soft string in a spiral with the turns sepa- rated one from the other by a small interval. This is necessary for an even callusing and the raffia must be moist (fig. 4B). Other types of grafts suitable for sand callusing can be made by machines, but they are inferior to skillfully made hand whip grafts. With rootings as stocks, instead of cuttings, the various operations described above are the same except that the roots should be cut off as close as possible from the original cutting. The grafts when made are tied with a No. 16 wire, in bundles of 25, and set at a slight slant in a sand pit with a southern exposure and protected from rain. The sand should be coarse, free from silt, and contain about 5 per cent of moisture. About 2 inches of sand should cover the top of the scions. The grafts are ready for planting in the nursery when they are well callused. CiRC. 288] PHYLLOXERA RESISTANT VINEYARDS 15 For hot room callusin^, the short or modified whip graft should be used. To make it, a grafting knife or a whip grafting machine can be used. The stocks, cuttings or rootings, prepared and graded, are cut with a knife so as to give a cut about II/2 times their diameter. The tongue is made by cutting across the grain and extending from near the top of the cut to near its bot- tom level. It should be fairly thin so as to avoid splitting. The scion is prepared in the same manner and adjusted to the stock. When the graft is well made, it is very solid and does not require tying (fig. 4A). There are several satisfactory machines for making the modified whip graft. The one shown in fig. 5 has been used with suc- cess at the University Farm. It shapes a stock or a scion cutting at a single stroke, so that a graft can be made with two strokes. A double action machine of the same type makes a graft with one stroke. The united grafts are put into boxes for callusing in a hot room. The boxes may be of any size, except for the height, which is regulated by the length of grafts. An 18-inch height will accommodate grafts made with 10- or 12-inch stocks. A hinged side is very convenient for filling and emptying the boxes. The callusing medium consists of a mixture of saw^dust and coarse ground charcoal — three parts of the former to one of the latter give a good callusing mixture. Further- more, the boxes must be lined on all sides except the top with a 2-inch layer of moss. For filling them, a little moss is put on the bottom and sides, and a single layer of grafts laid down horizontally, with the scions toward the top of the box and at the same level (fig. 6). The butts rest on the moss at the bottom of the box. The callusing mixture is used to fill the space between the grafts, and then another layer of grafts is put on the first, and so on until the box is filled. During this process, the layer of moss is raised gradually on the sides and bottom, and when the grafts are 2 inches from the hinged side thej^ are covered with moss. The hinged side is then closed and the box put in its normal position. To insure good packing in the box, necessary for good callus- ing, water is poured freely into the box and sufficient callusing mixture Fig. 5. — Grafting machine making the modified ^vllip graft. 16 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION added to just cover the top of the scions. The box is allowed to drain and is then covered with a 2-inch layer of callusing mixture, slightly moist. At this stage, the box is ready to enter the hot room. It may be kept in a cool place if delay of callusing is desired. wm^msmm 'iS:«Pfeg %^ '^^^ Fig. 6. — Callusing box showing method of filling. CiRC. 288] PHYLLOXERA RESISTANT VINEYARDS 17 The callusing room may be of various forms, but must be built so as to insure a uniform temperature. The same principle applies to the heating system. A coal oil stove and a two-bulb electric stove have been used v^ith success at the University Farm in a small room. At a temperature of 75° F., callusing takes place within three weeks, while at 85° F., the maximum, it is obtained within two weeks. At the higher temperatures the callus formed is delicate and easily injured by any unfavorable conditions. No callusing takes place below 60° F. From 70° to 75° F., are the most favorable temperatures. During the time the grafts spend in the hot room, they must be dipped occasionally in water of the same temperature as that of the room in Fig. 7. — Dipping vats, steam and water pipes. The white line shows the level of grafts in the callusing box. order to keep the butts continually moist. Care must be taken not to allow the water to reach the level of the unions because too much moisture prevents the production of callus (see fig. 7). Two dippings are generally sufficient during callusing. The cover must be kept rather dry, but may need to be wetted slightly from time to time. When the callusing is complete, the grafts are gradually accustomed to the outside temperature by passing several days in a room where the temperature is several degrees lower than that of the hot room. Then the boxes are set under an open shed and the hardened grafts are ready for planting. Nursery Grafting. — This operation can be done at two different seasons of the year. Cuttings planted in the spring in the nursery can be grafted during August and until about September 10, or grafted 18 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION in February or March. In the first case, the Yema graft should be used exclusively. This type of graft is made in three ways. In the ordinary Yema or ''bud" graft, the bud carries a certain amount of wood, unlike ordinary buds. The stock is cut as shown in fig. 8, II, by means of a special budding knife, so as to make a groove which will receive the scion. The bud is removed from the scion canes in the same way as the stock is cut (fig. 8, I), except that cut No. 3 is made so as to get a plane surface below the bud. It is then inserted on the stock and tied as shown in fig. 8 II. Fig. 8. — Yema grafts. (1) How to remove a bud from the scion cane. (2) How to cut the stock, insert the bud and tie the graft. (3) How the graft should be mounded up. (4) Modified Yema graft. (5) Knife used in Australia for Yema grafting. (6) New Modified Yema graft. The modified Yema graft needs no tying, and is more quickly made than the ordinary. For preparing the stock, three cuts as a minimum are necessary, but to remove the scion two are sufficient (fig. 8, IV). These two methods of Yema grafting are equally successful. The third method shown in figure 8, VI, is the easiest of all to make by hand and it has given very good results. It is essential that it should be tied below the eye and especially above. Raffia, small white string, and then strips of rubber are used as tying materials. To get good results, the stock must be well in sap at the time of grafting, while the buds must be taken from parts of canes that show a ripe or dead leaf color. CiRC. 288] PHYLLOXERA RESISTANT VINEYARDS 19 The grafts must be covered by mounding 3 inches of dirt above the buds and as soon as possible after having been made or they will part. The top of the vine is not cut at the time of grafting but before sprouting in February or March. The bud remains dormant until the starting of the sap in the spring. One-year-old resistant vines in the nursery can also be grafted in the spring ''in situ." The best methods of grafting are the ordinary whip graft already described, and the Yema graft. Stocks and scions are generally dormant although it does not matter if the former are already sprouting. In whip grafting, a scion with one bud only should be used. Unlike Yema grafting in the fall, in the spring the stock Fig. 9. — Yema grafting machine. must be cut off immediately after grafting, one-half an inch above the top of the bud. With both methods all scion buds must be covered by a wide mound 2 or 3 inches high above the buds. The ordinary Yema graft can be made by a machine which works satisfactorily. This machine is particularly handy for cutting out the buds. It can be obtained from Ulysse Fabre, Vaison (Vaucluse), France (fig. 9). Numerous suckers are likely to be thrown out in nursery grafting and it is very important to remove them as soon as they appear. Planting and Care in Nursery. — The planting of ungrafted resist- ant stock cuttings does not differ from that of common cuttings. They can be planted by hand, in trenches opened with the shovel or with suitable machinery, according to the scale of the planting. For bench grafts, more care is necessary. First of all, at the removal from the callusing boxes, they must be looked over one by one. All suckers from the stock must be cut close, and scion roots as well. When the scion buds are several inches long and whitish, it is a good practice to cut them back to about one inch in length. Trimmed in this 20 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION manner, the grafts, whether or not they have roots at their base, are ready for planting in trenches dug to a depth equal to the length of the grafts. A planting board as guide measuring approximately 16 feet by 4 inches by 1 inch marked with a saw about every 3 or 4 inches, and easily held in place by an 18-inch cross piece at each end by means of a spike, is indispensable for planting bench grafts. Each graft is placed opposite a notch, with the union placed just above the guide and in contact with it. This insures even spacing and a straight line (fig. 10). Care and regularity in these respects are very important Fig. 10. — (a) Planting board, (h) Diagram showing use of planting board with bench grafts. for success. When a planting board has been filled, the grafts are ''kept'' in their position by dirt thrown into the trench, so that the board can be removed to another portion of the trench. Water should be used at this time to settle the ground firmly at the base of the grafts. The trench is filled and a wide mound two inches high above the scions is formed with loose soil. Nothing will have to be done to the grafts until July when the shoots will measure several inches above the mound. At this time, it is necessary to cut off scion roots and to sup- press any suckers that have formed. For these operations, the mound is opened and then replaced as soon as they are performed. An irriga- tion should follow this work within a day or two. Toward the end of August, the grafts should be gone over again in the same way, but this CiRC. 288] PHYLLOXERA RESISTANT VINEYARDS 21 time the mound should be lowered so as to allow the unions to harden. If mildew is feared, the grafts should be sulfured. At this time, the nursery should be looked over by a man familiar with vine leaves to verify that the grafts are not mixed. Digging and Selection of Stocks. — The vines in the nursery can be dug up as soon as they have lost their leaves. In a small nursery the vines can be taken out conveniently by using a plow to remove as much dirt as possible along the rows of vines on one side, and then by means of a shovel the grafts can be removed without injury. In large nurseries, the vines are dug up by means of a nursery digger and tractor. The digger cuts the roots, loosens the vines, and lifts them a few inches so that they can be easily pulled out by hand. The vines should now be graded. As the top growth of rootings is proportional to the size of the root system, their grading could be made safely from this part of the vine. For ungrafted resistant stocks, grade No. 1 corresponds to vines having a minimum of four well dis- tributed and developed roots near the base, and a normal top growth (see fig. 11a) ; grade No. 2, to vines with less than four good roots or with a small top growth or slightly injured on the trunk; grade No. 3, or culls, is made up of weak vines which should be destroyed. Grafts are sorted like ordinary rootings for top growth, and root growth, but the unions should also be considered. A No. 1 graft should have a complete, smooth, and solid union, a uniform root system of four to five roots, and a corresponding top growth (fig. 115). Any vine with one of these parts defective is a grade No. 2 vine. Growers should, whenever possible, plant only vines of No. 1 grade, as experiments have shown that they succeed much better than grade 2, and come into bearing earlier. PLANTING GRAFTED VINES Owing to the nature of a grafted vine certain precautions relative to planting operations are necessary to insure the success of a vineyard on resistant stocks. First of all, a thorough and deep preparation of the soil is essential for the proper development of these vines. It is well to consider that the root system of resistant stocks is weaker generally than that of ungrafted vines, and needs more thorough soil preparation. The soil should be stirred to a depth at least equal to the length of grafts. This work can be done in two ways : (a) by plow- ing all the ground to a depth desired, (&) by subsoiling every two or three feet to a depth of 18-30 inches according to the type of soil 22 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION and its moisture content, and plowing 10-12 inches deep. Grafted vines should be *' heeled in" carefully from the time they are dug from the nursery until they are ready for planting out. The union should always be covered in order to prevent drying while the grafts are heeled in. Fig. 11. — (a) No. 1 rootings. (h) No. 1 bench grafts. CiRC. 288] PHYLLOXERA RESISTANT VINEYARDS 23 At planting time, the grafts (fig. 12a) are taken from the bundles one by one, and their base roots cut to three or four inches for planting in holes (fig. 126), or to one-fourth of an inch for planting with a dibble. Other roots appearing at nodes or on the scion should be cut very close. All the growth made by the scion except the best cane is removed and this cut to a stub with two buds. After this preparation, the grafts are placed in a 5-gallon oil can with a few inches of water, and taken out one by one as they are planted. Fig. 12. — (a) Bench graft before trimming, (b) Bench graft ready for planting, (c) Bench graft planted. In planting in a hole, the roots should always rest on good mellow soil, and the union should be placed at one and a half inches above the level of the ground. This is to prevent the scion from sending out roots which would destroy the value of the grafted vine. Loose dirt is thrown on the roots till the hole is one-third filled and then firmed with the foot. The hole is almost filled up, stamped a second time, and a wide mound of loose dirt about two inches above the top of the graft is made (fig. 12c). This mound must not be disturbed until the shoots have come out and are six or eight inches long. 24 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION When grafts are planted with a dibble, the soil should be firmed around the base, and a mound built around the vine as above. With good grafts in good condition and the work properly done as explained, as good a stand is obtained as with ungraf ted vines. FIELD GRAFTING When ungrafted resistant vines have been planted in the vineyard they should be grafted as soon as they are sufficiently large. This condition is generally reached in one year, but some growers prefer to graft when the stocks are two years old. The ordinary whip-graft method is used almost exclu- sively. In this case, a scion with two buds is used instead of one, as in bench grafting and nursery grafting. When stock and scion are of the same size, a perfectly smooth graft can be made (fig. 13A). If the stock is larger than the scion, the stock should be whip-grafted on the side (fig. 13, B and C). The grafts should be tied with raffia soaked in water. Whip grafting in the field should be done from February 1 to April 15 according to the region, and the soil, which should be in good friable condi- tion and not too wet. The Yema graft can also be used. The Yema graft in the fall is especially suitable for field grafting. If a few vines do not take, it is possible to regraft them in the spring according to the ordinary whip- graft method. By the combined use of a.. Whip ^aft wHh stofrand these two grafts a very good stand can be scion of equal diameter. B , , . T . and C. Whip graft of a stock obtained m one year. larger than the scion. 15?n-5,'25