UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION CIRCULAR No. 226 December, 1920 PROTECTION OF VINEYARDS FROM PHYLLOXERA By FBEDEKIC T. BIOLETTI The phylloxera is a minute insect which attacks the roots of the vine, and which has destroyed about 100,000 acres of vineyard in California alone. It has found its way into parts of the coast counties from Mendocino to San Luis Obispo and of the interior counties from Yuba and Glenn to Tulare. It spreads slowly but surely in the in- terior and somewhat more rapidly in districts nearer the coast. Means of Dispersal. — The phylloxera's most rapid method of spreading to new vineyards is by means of the winged form which appears occasionally in the cooler districts, but apparently never in the warmer interior. It is usually introduced into new districts by means of rooted vines brought in from infested areas. It may also be brought in with cuttings, boxes, implements, and even boots that have been used in infested vineyards. It spreads very slowly from vine to vine below ground on the roots and more rapidly, sometimes, by crawling short distances over the surface of the ground. Quarantine. — The spread of phylloxera can be much delayed by disinfecting all material — vines, cuttings, boxes, implements — coming from a suspected locality to an uninfested vineyard. Cuttings and rooted vines can be disinfected by treatment with water at 122° F. for five minutes as follows: Equipment : 1. An accurate dairy or other thermometer indicating to 212° F. 2. A cauldron of a capacity of twenty to thirty gallons, or a small boiler. 3. Two fifty-gallon wooden barrels, open at one end, or any other containers of that capacity. 4. A fork for the quick and easy removal of the treated stock from the disinfecting barrels. Method of procedure : Cuttings in bundles can be disinfected without any preliminary treatment. Rooted vines should first be pruned, then washed to remove soil, and tied up in bundles of about 100. The disinfection is carried out as follows: Place one bundle of rooted vines in barrel A, filled two-thirds full with water at 104° F., and leave it for two minutes. Then remove the bundle from barrel A and place it in barrel B, containing water at exactly 122° F., and leave Z UNIVERSITY OF CALIFORNIA EXPERIMENT STATION for five minutes. Stirring the bundles in the heated water will make the sterilization more effective. No part of a bundle should be allowed to be above the surface of the water. Great care should be taken in keeping the water of barrel B at 122° F. This can be easily done by adding a little boiling water from the cauldron between treatments of bundles. The temperature of the water of barrel A should be kept at about 104° F. A drop of a few degrees in barrel A, however, is of slight consequence, as this barrel is used merely to give the bundles of vines a preliminary warming in order that they will not cool the water in barrel B below 122° F. A watch or other timepiece placed in a suitable position is necessary for accurately timing the immersion. The disinfected cuttings or rooted vines must be packed in phylloxera-free packing material and can then be planted safely or shipped into any district. Probability of Infestation. — The probabilities of infestation vary from zero to certainty. In excessively sandy soils, such as the blow sands of parts of the San Joaquin Valley and of southern California, the phylloxera can not live and the vines are safe. In soil from which vines killed by phylloxera have just been removed any new vines planted are certain to be infested from the start and are likely to die before they produce a single paying crop. Between these extremes all degrees of probability occur. In heavily infested parts of the coast region, such as Sonoma, Napa, and Santa Clara counties, it is unsafe to plant non-resistant vines, except perhaps in a few isolated mountain valleys well protected from the winged insect by a screen of hills and woods. In other parts of this region single vineyards are fairly safe if the indicated precautions against the introduction of the insect are taken. Where many vineyards are planted near together, however, some grow- ers are very apt to neglect these precautions and phylloxera introduced into one vineyard will rapidy spread to neighboring vineyards. In the San Joaquin Valley it is seldom advisable to use resistant roots, except in the districts where the phylloxera is known to occur. Even in these districts it is probably best not to plant them in new land if a mile or more from an infested vineyard. If the soil is more or less sandy, deep, rich, and well supplied with water for irrigation, the danger of rapid infestation and destruction of the vines is less. In heavy loams and clay soils the danger is greater. In counties and sections which appear to be free from phylloxera no resistant vines should be planted, even for experiment purposes, unless carefully disinfected under the direction of a horticultural com- missioner. Phylloxera may be carried and will breed on resistant roots. This makes these roots dangerous in an uninfcsted district, as they may spread the pest without showing any signs of damage themselves. Resistant Vines. — The roots of certain American vines are practi- cally uninjured by attacks of the phylloxera and can be used as graft- ing stock to protect susceptible vines. All the varieties of vines that we grow for grapes are susceptible. The grapes of resistant vines are CIRCULAR 226 PROTECTION OF VINEYARDS FROM PHYLLOXERA 3 of no value, but varieties grafted on them produce the same grapes as when ungrafted. When to Use Resistant Vines. — The use of resistant roots is insur- ance, and like most insurance has a cost. They should be used there- fore only when their cost is considerably less than the probable loss from the use of non-resistant roots. This may be estimated if we know the probable duration of the two kinds of vineyards. The duration of a non-resistant vineyard depends on a number of conditions con- sidered in the discussion of the probability of infestation. Let us suppose that a vineyard, resistant or non-resistant, would remain profitable for twenty years if there were no invasion of phylloxera. Let us assume for one set of conditions that the non-resistant vineyard would be destroyed by phylloxera in ten years, and, for another set, in twenty years. Estimates might then be made as follows : A. Non-Eesistant Vineyard — Probable Duration, 10 Years Cost of establishing, per acre $200 Total profit (6 crops) 600 Loss of vineyard at 10 years 200 Total net profit - 400 Annual net profit 40 B. Non-Eesistant Vineyard — Probable Duration, 20 Years Cost of establishing, per acre $200 Total profit (16 crops) 1600 Loss of vineyard at 20 years 200 Total net profit 1400 Annual net profit 70 C. Eesistant Vineyard — Probable Duration, 20 Years Cost of establishing, per acre $300 Total profit (16 crops) 1440 Loss of vineyard at 20 years 300 Total net profit 1140 Annual net profit 67 A consideration of these estimates indicates that if a vineyard is liable to infestation and destruction in a short period, say ten- years, the extra cost of planting and handling resistant vines would be justi- fied. On the other hand, if the vineyard were reasonably safe from infestation for a long period, say twenty years, the extra cost of re- sistant vines would be wasted. Skill and Experience Needed. — The estimates of the relative profits of resistant and non-resistant vineyards given above are based on an increased first cost of the resistant vineyards of $100 per acre and an annual increased cost of handling of $10. It was further assumed that the crops of each would be the same. These assumptions are true only for particular cases. If the grower lacks skill and experience in the use of resistant vines his cost may be greater and his crops will certainly be less. On the other hand, a skillful grower who knows how to choose, plant, and handle a resistant vineyard may reduce the cost considerably and in 4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION many cases increase the amount and quality of the crop. No grower should attempt to grow a vineyard of resistant vines, however much experience he has had with ordinary vineyards, without thoroughly studying the subject. He should consult his farm advisor, read the publications on the subject issued by the College of Agriculture, and visit nurseries and vineyards where resistant vines are handled. He should know what varieties of resistant stock are most likely to give profitable results in his particular soil and climate and with the variety of grape he desires to grow. He should know how to recognize a good resistant grafted vine, how to plant it, and how to care for it in the vineyard, and he should, if possible, obtain some practice in all branches of the work. ■ With this preparation, a good farmer can safely plant a resistant vineyard and in many cases the extra cost will be returned by im- proved crops, even though the phylloxera never gets into his district. Without this preparation he is practically sure to make a partial or a complete failure. Best Resistant Stocks. — Hundreds of different resistant stocks have been tested and used to some extent. Only a few dozen have been used on a large scale. Only two, Rupestris St. George and Lenoir, have been used much in California. Most of the stocks which have given satisfaction in Europe have been tested at Davis, California, for over ten years and the results make it possible to recommend several stocks as better than the two most commonly used here. In fact, our most widely grown stock, the Rupestris St. George, has given the poorest average results of the eighteen stocks tested as regards crop and vigor. The Lenoir has a good record at Davis, but is not sufficiently resistant and has failed in many vineyards. The stocks which can be most safely recommended are : 1. Chasselas X Berlandieri 41-B, usually called "41-B" for short. This stock has given the best results with more scion varieties than any other. These varieties include Muscat, Black Corinth, Sultana, Tokay, and Cornichon. Its grafts bear well and are vigorous and long lived. It suffers less from drought than most stocks. 2. Riparia X Rupestris 3309, usually referred to as "3309." This stock follows close to 41-B and is somewhat easier to graft. It has given the best results with Sultanina (Thompson), Emperor, and Palomino, among others. 3. Riparia X Rupestris 3306, referred to as " 3306. ' ' This has been the best stock for Malaga and White Corinth. These stocks have been well tested only at Davis and at Kearney, but there seems every reason to suppose that they will be found ex- cellent for most or all other parts of California where grape growing is feasible. They have, with all varieties, in all cases given better results than St. George or Lenoir, with one exception, the raisin Muscat. This variety is hard to suit in the matter of a stock and many cases of failure are reported from the numerous countries where it is grown. It usually bears well when grafted, but the grafted vines on most stocks are short lived. Its record at Davis on 41-B is excellent. It lacks vigor and bears poor crops on 3309 at Kearney, where St. George has given better results, though its durability on this stock is in doubt.