Division of Agricultural Sciences 
 
 UNIVERSITY OF CALIFORNly 
 
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 NEMATODES and their 
 Control in VINEYARDS 
 
 Mr 
 
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 ■*''♦ 
 
 . H. HART 
 ; N. KASIM 
 
 
 1CULTURAL 
 
 Station 
 
 e r v i c e 
 
 CIRCULAR 533 
 
 Revised 
 
 CAECAG 533 1-20 (1973) 
 
Nematodes and Their Control in Vineyards 
 
 THIS CIRCULAR provides information on nematodes in vineyards for 
 growers, chemical company representatives, and others interested in grape 
 production. Specifically, it deals with the following: 
 
 • General description of nematodes 
 
 • How they injure plants 
 
 • What species are found in California vineyard soils 
 
 • Brief life histories of prevalent species 
 
 • Control measures, including preplant and postplanting 
 soil fumigation, and use of resistant rootstock varieties 
 
 November 1973 
 
 THE AUTHORS 
 
 D. J. Raski is Professor of Nematology and Nematologist in the Experiment Station, 
 Davis; W. H. Hart is Extension Nematologist, Davis; and A. N. Kasimatis is Exten- 
 sion Viticulturist, Davis. 
 
 THE COVER PHOTO shows the application of fumigant under continuou 
 prior to planting a vineyard. While the University does not yet recommend tl 
 fairly common practice in the coastal areas. 
 
Scope of the Problem 
 
 All grape varieties grown on their own 
 roots and most common grape rootstocks 
 used for commercial propagation may be 
 attacked by several kinds of plant-para- 
 sitic nematodes which are widely distri- 
 buted in California. These nematodes also 
 attack many other agricultural crops and 
 ornamentals and have been spread by 
 transplants and plant divisions of many 
 crops in soil on plants or agricultural ma- 
 chinery and in irrigation water. Studies 
 of nematodes and the experience of 
 growers indicate that nematodes on grape 
 can be a problem in any area of the state 
 where grapes can be grown successfully. 
 The importance of the root knot nematode 
 in grape production has been recognized 
 for many years. However, we now know 
 that these nematodes, as well as other less 
 obvious species, do much more harm than 
 was realized. We have more complere 
 knowledge about the wide distribution of 
 plant-parasitic species in vineyard soils. 
 At the same time, growers increasingly 
 have been replanting grapes in old vine- 
 yard sites that have reached a stage of 
 declining productivity or on old agricul- 
 tural lands formerly used for tree crops 
 or for nematode-susceptible vegetables 
 and field crops. 
 
 Vines may produce satisfactory yields 
 for long periods, even though nematode 
 populations are increasing, if other fac- 
 tors such as soil, water, and cultural 
 practices are favorable. Even old and 
 heavily infested vines may remain pro- 
 ductive under optimum cultural condi- 
 tions. However, the high nematode popu- 
 lations will attack, stunt, or kill young 
 vines when such soils are replanted. 
 
 Studies under controlled greenhouse 
 conditions have demonstrated that many 
 nematode species injure grapes (table 1) . 
 Field experiments with established nema- 
 tode populations have provided additional 
 evidence and have demonstrated the bene- 
 fits of proper soil treatment before re- 
 planting. 
 
 Studies have shown that certain nema- 
 todes formerly not known to be damaging 
 to grapes may cause serious injury. These 
 include species which do not enter root 
 tissues but feed on roots while remaining 
 in the soil. One such species also carries 
 and transmits certain virus diseases of 
 grape and is an important factor in the 
 persistence of these diseases in vineyard 
 soils. 
 
 What Nematodes Are 
 
 Nematodes are slender, active, worm-like 
 organisms. Like insects, nematodes differ 
 greatly in habits, size, and appearance. 
 The smallest plant-parasitic forms are 
 about Y25o inch long, while the adults of 
 certain animal parasites can grow to be 
 several feet long. 
 
 The typical, or basic, body form of 
 nematodes is long and cylindrical, with 
 the body tapering at both ends to the head 
 and tail. In a number of plant-parasitic 
 forms, the adult female becomes a swollen 
 pouch-like organism, lemon-, pear-, kid- 
 ney-, or irregularly-shaped, depending on 
 
 species, while the male remains slender 
 and worm-like. 
 
 Plant-parasitic species are very small, 
 averaging only about % 4 inch in length; 
 and structural features, even body shape, 
 can be observed only with a microscope. 
 These species vary not only in the appear- 
 ance of the adults but in the way they live 
 and feed. Feeding is accomplished by 
 means of a hollow needle-like mouth part 
 (the spear or stylet), which is used to 
 puncture the cells of plant tissues and ex- 
 tract the contents. 
 
 [3] 
 
All plant-parasitic forms begin life as 
 eggs, deposited by females in plant tissue 
 or in the soil, singly, or in egg masses 
 held together by a jelly-like material each 
 of which may contain more than 500 
 eggs. Larvae form within the eggs, hatch, 
 and go in search of suitable plant tissues 
 on which to feed. Larvae undergo several 
 moults, increasing in size until the adult 
 stage is reached. In some species the larva 
 which hatches from the egg is the only 
 stage that can move and is the infective 
 stage. In other species, all stages from 
 young larvae to adults can move freely 
 and are equally infective. 
 
 Nematodes that attack grape represent 
 virtually all types of plant-parasitic 
 species. Some are endoparasites; that is, 
 
 they live most or all of their lives inside 
 the roots. There, they are protected by 
 layers of root tissues against adverse soil 
 conditions and chemical soil treatments. 
 Others are ectoparasites — feeding on ten- 
 der root tissues, while most or all of their 
 bodies remain in the soil outside the roots. 
 These species are more vulnerable to soil 
 treatment of established plants, since their 
 bodies are not protected by root tissues. 
 Migratory nematodes are those whose 
 adults and larvae move freely through 
 soil and root tissue. Sedentary nematodes 
 have larvae that move freely, but the 
 adult females are swollen organisms that 
 cannot move. Listed here are the nema- 
 todes infecting grape, grouped according 
 to their types: 
 
 Type 
 
 Endoparasites 
 
 Ectoparasites 
 
 Migratory 
 
 Root lesion nematodes 
 (Pratylenchus spp.) 
 
 Dagger nematodes 
 
 {Xiphinema spp.) 
 Ring nematodes 
 
 (Criconemoides spp.) 
 Pin nematodes 
 
 (Paratylcnchus spp.) 
 Spiral nematodes 
 
 (HeUocotylenchus spp.) 
 
 Sedentary 
 
 Root knot nematodes 
 (Meloidogyne spp.) 
 
 Citrus nematodes 
 (Tylenchulus 
 semipenetrans ) 
 
 How Nematodes Injure Plants 
 
 Nematode infestations destroy plant roots 
 which result in weak top growth and re- 
 duced yields. When young plants are 
 placed in heavily infested soil, root growth 
 may be completely prevented and the 
 plants may never become established. 
 This injury may take place in a number 
 of direct and indirect ways. 
 
 The most obvious means by which 
 nematodes injure plants is the mechanical 
 penetration and feeding on roots by large 
 numbers of nematodes. As many as 2,000 
 to 10,000 root lesion nematodes may be 
 
 present in one gram of root. A single gall 
 induced by root knot nematodes may con- 
 tain more than a dozen females, each cap- 
 
 able of producing 600 eggs, and these 
 galls may be so close together on young 
 roots that they resemble a string of beads. 
 The impact of sheer numbers of nema- 
 todes, therefore, has a significant effect on 
 plant growth. 
 
 Nematodes play an important part in 
 allowing entry for secondary decay or- 
 ganisms into roots. The wounds made in 
 roots by the entry and feeding of endo- 
 parasites. together with the weakened con- 
 dition of such roots, enable other soil or- 
 ganisms, fungi, and bacteria to enter the 
 roots, which they may not have done 
 otherwise. 
 
 In feeding in or on roots, nematodes 
 
 [4] 
 
puncture cells of the root and withdraw 
 part or all of the cell contents. During this 
 process the nematodes inject salivary 
 fluids into the cell. The function of these 
 secretions is not understood completely, 
 but the effects can be seen readily in some 
 cases. The growth of cells, even those 
 some distance from the cell actually fed 
 upon, often is changed radically. Cells 
 may be killed, stop normal growth, or 
 begin to enlarge or divide abnormally. 
 The conductive tissue which supplies 
 water and soil nutrients to the plant tops 
 often is blocked, and both root and top 
 growth is suppressed. 
 
 Certain ectoparasitic nematodes trans- 
 mit specific virus diseases during feed- 
 ing on grape roots. These nematodes now 
 are known to be responsible for the per- 
 sistence of certain viruses in soil for sev- 
 eral years even after diseased host plants 
 have been removed. Only a few nema- 
 todes are required to transmit the disease 
 to new plants, and the virus persists in 
 the nematodes for considerable periods. 
 
 Above-ground symptoms of nematode 
 injury to established plants, except for 
 symptoms of nematode-transmitted virus 
 diseases, usually are similar both to the 
 effects of other root-destroying organisms 
 and to any adverse soil or cultural condi- 
 
 tion which results in reduced growth and 
 productivity. 
 
 Root symptoms of nematode infestation 
 are more characteristic than those seen 
 above ground, but they vary with dif- 
 ferent nematodes, degree of infection and 
 the response of the host plant. 
 
 Root knot nematodes 
 
 Meloidogyne spp. produce swellings or 
 galls on roots. Infection occurs in young 
 rootlets, but galls may persist on older 
 roots. Heavy infections may completely 
 destroy the root systems of young plants. 
 Galling of roots blocks the flow of water 
 and food, thus starving the plant. Those 
 parts of the roots beyond the point of at- 
 tack often die. Root knot nematodes occur 
 throughout California but cause more se- 
 vere injury in light coarse-textured soils 
 than in loam and clay soils. 
 
 The root knot nematodes have been 
 known since about 1850 and have been 
 described under a variety of popular and 
 scientific names. The most common of 
 the former have been root knot or garden 
 nematodes or eelworms. About a dozen 
 species and varieties of root knot nema- 
 todes are now known to exist. At least 
 five are known in California; three have 
 been found on grape. (See table 1.) 
 
 Table 1 
 NEMATODES OF IMPORTANCE ON GRAPE IN CALIFORNIA 
 
 Name of Nematode 
 
 
 Common 
 
 Scientific 
 
 Distribution 
 
 Root Knot: 
 
 Cotton 
 
 Meloidogyne incognita 
 
 Common 
 
 Mostly in warm soils of the San Joaquin Valley 
 
 and in southern California 
 Uncommon on grape but not on other crops 
 
 Common 
 
 
 
 
 Pratylenchus vulnus 
 
 Dagger: 
 
 American 
 
 (none) 
 
 Citrus 
 
 Xiphenema americanum 
 
 Common 
 
 Tylenchulus semi- 
 
 
 
 
 
 
 Tulare, and Riverside counties. 
 
 transmits the fanleaf virus disease complex. 
 
 [5] 
 
Root knot nematodes are sedentary 
 endoparasites. Females within root galls 
 deposit a large number of eggs in a jelly- 
 like material referred to as an egg mass. 
 Larvae form within the eggs and hatch 
 when soil conditions are suitable. When 
 soil conditions are unfavorable, many 
 larvae remain within the eggs and can 
 survive for several years. Free larvae in 
 soil, in the absence of a suitable host 
 plant, can survive for at least a year under 
 normal soil conditions. 
 
 After hatching, the young infective 
 larvae move through the soil or root tissue 
 to a suitable root or to new areas of the 
 root. Movement of individual larvae is 
 limited to a few inches. In general, roots 
 grow to the nematodes, since their move- 
 ment is limited. Infective larvae penetrate 
 young rootlets near the growing point. 
 Some penetration also occurs in areas 
 where roots have been injured. 
 
 Once within the root, larvae establish 
 themselves and begin to feed. At this 
 point they are incapable of further move- 
 ment except for the head in feeding. Dur- 
 ing development, larvae swell, first be- 
 come flask-shaped and finally, after sev- 
 eral moults, become adults. Adult females 
 are soft-bodied and pear-shaped and are 
 pearly-white at maturity. These are the 
 so-called "pearls" which growers and 
 home gardeners often see in cut sections 
 of galls from fleshy-rooted plants. Adult 
 males develop within the bodies of flask- 
 shaped late larval stages; at maturity 
 they are once again elongate worm-like 
 bodies able to move about. Males are not 
 necessary to continued reproduction of 
 the nematode. Development of males ap- 
 pears to be associated with vitality of the 
 host plant. More males are produced on 
 declining or heavily infested plants than 
 on lightly infested ones. 
 
 The number of generations per year of 
 root knot nematodes is governed by soil 
 temperature in the presence of suitable 
 hosts. Generations may develop almost 
 continuously in warm areas under favor- 
 able conditions. In temperate regions, the 
 
 number of generations varies from one 
 to two per season in the north to as many 
 as five to eight in the south. In hot desert 
 areas, reproduction may be reduced by 
 lack of moisture, even though favorable 
 temperatures may be present for a longer 
 period. In general, root knot nematodes 
 can grow and reproduce at any tempera- 
 ture suitable for growth of susceptible 
 host plants. 
 
 Growth of young rootlets may be corn- 
 
 Root knot nematode: infectious larva (top) finds 
 young feeder roots and enters them. Inside the 
 roots it swells (center) and, on maturity, deposits 
 eggs in masses either inside or outside the root 
 (bottom). The eggs hatch to become infectious 
 larvae. Actual length about 1 /60th inch. 
 
 6] 
 
pletely stopped when larvae enter. In the 
 root area where a larva is feeding, cells 
 enlarge and cell walls eventually collapse 
 leaving large abnormal "giant cells" on 
 which the nematode continues to feed. 
 Several such "giant cells" may be formed 
 around the head of each nematode. As 
 infection continues, changes occur in 
 other nearby cells, including conductive 
 tissues, which result in partial or com- 
 plete blocking of the flow of water and 
 nutrients. Depending on the root knot 
 species involved, the root below the site 
 of infection may die, and new rootlets 
 will be produced just above the infection 
 site which, in turn, will become infected. 
 The latter effect will eventually produce 
 an abnormally branched "hairy root" 
 condition. 
 
 Root lesion nematodes 
 
 Pratylenchiis spp. cause decaying areas 
 (lesions) on the large roots of some 
 plants that may become large enough to 
 be seen with the naked eye. On other 
 plants, including grape, they invade the 
 young rootlets injuring and often girdling 
 them. The system of small rootlets, which 
 is the plant's most important mech- 
 anism for the absorption of water and soil 
 elements, may be completely destroyed. 
 
 Root lesion nematodes occur on grape 
 throughout the state. Damage usually is 
 more severe on heavier, fine-textured soils 
 but also occurs in coarse-textured soils. 
 
 At least nine root lesion nematode spe- 
 cies are known in California, and are 
 among our most important nematode 
 pests on agricultural crops. (See table 
 1.) One species, Pratylenchus vulnus, is 
 known in many areas of the state on 
 grape as well as on other important tree 
 and vine crops. Infested plants lose their 
 vigor, and production is reduced. Young 
 plants placed in infested soil fail to pro- 
 duce satisfactory root systems and will 
 remain weak or die. 
 
 Another species, Pratylenchus neglec- 
 tus, is frequently found in soil samples 
 from grapevines. This species also has 
 
 The root lesion nematode spends its life cycle 
 feeding while moving through the root and deposit- 
 ing eggs singly. Actual length varies from about 
 l/30th to l/50th inch. 
 
 been found in a few declining vineyards 
 heavily parasitizing the roots of vines and 
 appears to be a serious pathogen in these 
 cases. A third species, P. thornei, also is 
 commonly found in soils with vineyard 
 potential, but this species has not been 
 found in grape roots and is not believed 
 to be of importance in vineyards. 
 
 Root lesion nematodes are endopara- 
 sitic and migratory. Adults as well as 
 larvae are worm-like in shape and are 
 able to move through the roots or soil. 
 Eggs are laid singly in root tissue while 
 females move through the roots feeding 
 on first one cell, then another. 
 
 [7] 
 
Dagger nematodes 
 
 Xiphinema spp. are large nematodes 
 of the ectoparasitic migratory type. They 
 do not enter the roots but remain in the 
 soil feeding on the suceulcnt tissue of 
 young root tips with their long needle-like 
 mouth parts (spears). Growth of young 
 rootlets is suppressed, and root tips often 
 become slightly swollen and somewhat 
 curved or sickle-shaped. Branching may 
 occur above the place of feeding, and re- 
 peated feeding by large numbers of 
 dagger nematodes may form a dense mass 
 of abnormally branched, swollen and 
 darkened rootlets. 
 
 Two species of dagger nematodes occur 
 on grape and other crops in California 
 (table 1.). Both are distributed widely 
 in California and have similar direct ef- 
 
 The dagger nematode lives outside the roots and 
 feeds on them by inserting its long dagger-like 
 spear. Actual length about 1 10th inch. 
 
 fects on vines. One species, Xiphinema 
 index, also transmits the fanleaf-yellow 
 mosaic-vein banding virus disease com- 
 plex of grape. This nematode is respon- 
 sible for the reinfection with these viruses 
 of new grape plantings on old grape land, 
 even though several years may have 
 passed since the removal of old virus- 
 infected vines. The roots of such plants 
 which remain in the soil after old plants 
 are removed may remain alive for several 
 years providing food and a source of 
 virus inoculum for dagger nematodes 
 year after year. Xiphinema index is 
 found most commonly in coastal areas but 
 is also known in the San Joaquin Valley 
 as far south as Visalia and Delano. 
 
 Another, Xiphinema americanum, is 
 the most widely distributed dagger nema- 
 tode in California. In grape it is often 
 present only in small numbers and usually 
 in association with other nematode spe- 
 cies such as root knot, lesion, and ring 
 nematodes. Assessment of damage caused 
 by this species is difficult because of these 
 coincident infestations and because X. 
 americanum is difficult to rear under 
 greenhouse and laboratory conditions. 
 Field evidence indicates it is a serious 
 pathogen reducing plant vigor and pro- 
 ductivity. In some vineyards it builds up 
 to very high populations causing extreme 
 damage to and decline of vines. 
 
 Citrus nematode 
 
 Tylenchus semipenetrans was first dis- 
 covered in California in 1912 and subse- 
 quently has been found on commercial 
 citrus in most areas of the world where 
 the crop is grown. Other hosts include 
 olive, persimmon, and the grape, Vitis 
 vinijera. 
 
 While most of California's citrus ap- 
 pears to be already infested with the 
 citrus nematode, it has been found on 
 grape in only a few localities. Root symp- 
 toms on grape resemble those on citrus, 
 although its effect on vine growth or pro- 
 duction has not been evaluated com- 
 pletely. 
 
 [8] 
 
Citrus nematode sometimes is referred 
 to as an exposed sedentary endoparasite 
 but is treated in this paper as an ectopara- 
 site, because the body is never completely 
 covered by root tissue. Young larvae feed 
 on outer cortical layers of young roots 
 and begin to develop. As the females de- 
 velop through successive larval stages, 
 the head penetrates deep into the rootlet, 
 while the body outside the root enlarges 
 and becomes a variably-shaped curved 
 swollen structure on the surface of the 
 root. At maturity females deposit numer- 
 ous eggs in a jelly-like egg mass. Females 
 often occur in large numbers on infected 
 roots, and, since soil particles cling to the 
 jelly-like material containing the eggs, in- 
 fected roots appear crusted with soil 
 which does not shake off and can be 
 washed off only with difficulty. Males of 
 
 the citrus nematode remain small and 
 worm-like throughout life. Adult males 
 are only slightly larger than the larvae 
 that are to become females. Males do not 
 feed and are not necessary for reproduc- 
 tion. 
 
 Ring nematodes 
 
 Criconemoides spp. (ring) and pin ne- 
 matodes, Paratylenchus spp. (pin) nema- 
 todes are both migratory ectoparasites 
 which occur widely in grape and many 
 other crops and native plants in Califor- 
 nia. Ring nematodes are small but robust 
 and distinguishable from other nematodes 
 by their prominent cuticular rings. Pin 
 nematodes, in contrast, are very small 
 with delicate obscure rings. Both groups 
 have very long heavy spears in propor- 
 tion to the size of the body. Spear length 
 
 The citrus nematode, in its immature stages (center) lives outside the root. When it becomes an adult 
 (top) it penetrates the root with its head, leaving the tail end outside where it swells and produces eggs 
 (bottom). Actual length is about l/60th inch. 
 
 [9] 
 
Table 2 
 NEMATODES OP SUSPECTED IMPORTANCE ON GRAPE IN CALIFORNIA 
 
 Name of Nematode 
 
 
 Common 
 
 Scientific 
 
 Distribution 
 
 Root lesion 
 
 Ring: 
 
 ( none) 
 
 (none) 
 
 Pin: 
 
 (none) 
 
 (none) 
 
 Spiral: 
 
 (none) 
 
 (none) 
 
 Pratylenchus neglectus 
 
 Criconemoide8 xenoplax 
 
 Common 
 Common 
 
 Paratylenchus hamatus 
 
 Common 
 
 Helicotylenchus dihystera 
 
 Limited, according to present records 
 Limited, according to present records 
 
 
 in some species may be nearly half the 
 length of the entire body. 
 
 The life histories and habits of these 
 nematodes have not been completely in- 
 vestigated. Although they occur on roots 
 and in the soil around roots in large num- 
 bers, their effects on most plants are still 
 obscure. That they cause diseases has 
 been demonstrated in only a few cases. On 
 grape they may produce injury by their 
 feeding in large numbers, and they may 
 play a role in transmitting soil-borne dis- 
 eases or in weakening a plant so that it 
 becomes more susceptible to other 
 disease. 
 
 Spiral nematodes 
 
 Helicotylenchus spp. (table 2) occur 
 in many areas of the state around the 
 roots of many agricultural and native 
 plants. Normally they have been con- 
 sidered migratory ectoparasites but often 
 enter part way into the roots of some 
 hosts. In grape they recently have been 
 found entirely within roots and must be 
 considered at least partially endopara- 
 sitic. Recent laboratory studies have 
 shown that these two species multiply 
 readily in grape roots, but pathogenic 
 effects have not been determined. 
 
 How to Recognize Nematode Injury 
 
 Root symptoms of nematode injury may 
 be distinct as with root knot nematodes 
 but injury caused by other nematodes 
 is often obscure. Heavy infection often 
 is followed rapidly by secondary soil or- 
 ganisms which produce extensive decay. 
 The roots of young plants placed among 
 large populations of root knot nematodes 
 may die before producing characteristic 
 symptoms. Root lesion nematodes move 
 from decaying root areas to new sites. 
 When lesions produced by these nema- 
 todes have been invaded by secondary 
 
 decay organisms, the nematodes often can 
 be found only in the soil. 
 
 A field examination of vineyards or 
 other crops gives only superficial and un- 
 reliable evidence that nematodes may or 
 may not be a factor in the growth of that 
 crop or future crops. Root galls may be 
 found indicating the presence of root knot 
 nematodes, but other nematodes also may 
 be present which do not produce obvious 
 root symptoms. 
 
 Laboratorv examination of both roots 
 and soil usually is necessary to make 
 
 10 
 
sure of the presence of injurious species. 
 Both types of examination are required 
 to detect the presence of the wide variety 
 of nematode types known to attack grape. 
 Identification of both the nematode group 
 and species present is required. An ex- 
 amination which shows only the total 
 number of nematodes per acre is of little 
 value unless injurious species are identi- 
 fied from the mass of harmless or bene- 
 ficial species usually present in all soils. 
 
 Samples should be collected from sev- 
 eral areas within the vineyard or other 
 planting. Roots and soil from around the 
 roots should be taken from a depth where 
 moisture is uniform, usually at least 8 to 
 12 inches below the surface. Avoid sur- 
 face soil and roots near the surface, where 
 fluctuating temperature and moisture 
 may reduce nematode numbers to low 
 levels. 
 
 Samples should be taken and source 
 identified; vigor of the planting should 
 be noted. If growth is satisfactory or uni- 
 form over large areas, a number of sub- 
 
 Above: healthy grapevine roots. Below, left: roots injured by dagger nema- 
 todes, with distortions mostly on the tips of the rootlets. Below, right: roots at- 
 tacked by root knot nematodes; note absence of feeder roots and characteristic 
 swellings on the large as well as the feeder roots. 
 
samples may be combined to make a 
 single sample of a large area. In areas of 
 poor or questionable growth, however, 
 samples should be identified separately. 
 After collection, samples should be pro- 
 tected so that nematodes remain alive 
 until the sample is examined. Place soil 
 and roots in containers such as plastic 
 bags to prevent drying and do not allow 
 these containers to overheat in the sun in 
 the field, the hack of a car or truck, or 
 during storage. In shipment or transport, 
 samples can be protected in cardboard 
 boxes, insulated with newspapers, or in 
 inexpensive plastic foam chests. Make 
 sure that labels are complete giving (1) 
 name and address of grower, (2) name, 
 variety, and location of crop, (3) portion 
 
 or block which sample represents, and 
 (4) pertinent history of crop vigor and 
 previous crops. 
 
 Samples should be sent only to com- 
 mercial laboratories which have agreed 
 to perform the complete soil and root 
 examinations and species determinations 
 required. The University of California 
 performs a limited number of examina- 
 tions in conducting its own experimental 
 work and as an aid to farm advisors. 
 Limited examinations also are performed 
 by the California Department of Agri- 
 culture as an aid to county agricultural 
 commissioners. Neither the University 
 nor Department of Agriculture can pro- 
 vide laboratory services for normal agri- 
 cultural operations. 
 
 How Vineyards Are Affected 
 
 The ultimate result of heavy nematode progressively weaker each year. Attempts 
 
 infection on established grapes is weak- to provide increased or more frequent 
 
 ened vines and reduced yields. In a typi- water, more fertilizer and to lessen the 
 
 cal nematode situation, a few vines or crop load on affected plants by changed 
 
 areas of vines in a vineyard block become pruning practices may improve the plants 
 
 If your vineyard shows weak areas like the one pictured below, nematodes may be suspected. 
 
temporarily. Infected vines eventually be- 
 come weakened and less productive, are 
 removed, and new vines are set out. With- 
 out soil treatment these young plants 
 usually fail to grow satisfactorily or are 
 killed. Infested areas enlarge further and 
 eventually spread throughout most of the 
 vineyard. 
 
 Fanleaf virus further compounds the 
 problem. Vines are damaged both by 
 nematodes inhibiting good root develop- 
 ment and by systemic infection of a virus 
 
 disease. Control also is more difficult, be- 
 cause both the virus reservoir (the vine) 
 and the vector (the dagger nematode) 
 should be eliminated. 
 
 Many plant-parasitic nematodes are 
 widely distributed in grape and other 
 agricultural soils. Eradication from field 
 soils is impossible with present tech- 
 niques and may never be practical. The 
 problem thus becomes how best to live 
 with injurious species and reduce popula- 
 tions below damaging levels. 
 
 Control 
 
 Nematode control practices presently in 
 use are directed toward either providing 
 clean soil in which new vines may be 
 placed or restoring vigor and produc- 
 tivity to established vines. Preplant treat- 
 ments with various nematicides such as 
 the 1,3-dichloropropene (1,3-D) soil fu- 
 migants are well established, although 
 rates to be used and depth of application 
 still are being studied and modified. 
 Treatment of existing vines with di- 
 bromochloropropene (DBCP) soil fu- 
 
 migants is widely used, although research 
 suggests that vine improvement and in- 
 creased production can be expected only 
 when ectoparasitic nematode vulnerable 
 to this treatment are the principal species 
 present. Currently there is considerable 
 interest in systemic chemicals which 
 would be picked up by the plant from 
 foliage or soil applications, then moved 
 through the plant to the roots. A few 
 such candidate chemicals now are being 
 tested for effective systemic activitv, but 
 
 Effect of preplant fumigation on two-year-old Thompson Seedless grapevines: The plant on the left was 
 planted in fumigated soil, the one on the right was planted at the same time in untreated soil. 
 
 [13] 
 
results suggest poor and erratic control. 
 Neither the use of DBCP or systemic 
 nematicides have shown promise for con- 
 trol of the dagger nematode-fanleaf virus 
 disease complex in grape. 
 
 An overall program 
 
 A well-planned control program based on 
 careful analyses should include the use of 
 nematode- resistant rootstocks, virus- and 
 nematode-free planting material, and the 
 selection of the most effective soil treat- 
 ment for the particular type of nematode 
 infestation. Cultural controls such as crop 
 rotation and fallowing of the land are 
 not sufficient in themselves, but may be 
 used to obtain better chemical control. 
 
 Overall preplanting soil treatment of 
 large areas or blocks is advisable where 
 many vines are in a declining condition 
 or where previous replanting attempts 
 have resulted in a high percentage of 
 failures or weak vines. Such treatment 
 also may be advisable where other crops 
 such as orchard trees have been removed 
 or where transplants of susceptible an- 
 nual crops have been introduced and have 
 provided means of introduction and 
 build-up of nematode pests. 
 
 Spot preplanting treatment of single 
 vine replant sites, or of small areas, is 
 sometimes desirable. However, reinfesta- 
 tion of small areas from adjacent in- 
 fested vines will readily occur. 
 
 Chemical control 
 
 The use of chemicals in soil is restricted 
 by factors not encountered in the applica- 
 tion of chemicals to the tops of plants. Ne- 
 matode control materials move through 
 the soil as gases or as solutions or emul- 
 sions in water. The soil itself restricts dif- 
 fusion of these materials depending on 
 various physical and chemical factors 
 such as the amount of clay and organic 
 matter, soil temperature, and the amount 
 of soil moisture present. Agricultural soils 
 vary widely from area to area and within 
 a single field. Thus the amount of chem- 
 ical necessary per acre is difficult to ascer- 
 tain with accuracy and usually is decided 
 
 on the basis of the particular soil present 
 that is the most difficult to treat. The 
 depth to which effective treatment is de- 
 sired also influences application rates and 
 methods. While low rates and shallow 
 application can be used for shallow-rooted 
 annual crops, high to very high rates and 
 deep applications are necessary where 
 long-lived perennial plants, such as grape, 
 are to be grown. 
 
 Preplant soil treatments 
 
 Soil fumigants with 1,3-dichloropropene 
 ( 1,3-D) as the principal active ingredient 
 are the most widely accepted preplant 
 soil fumigants for field conditions. These 
 are available as D-D® (Shell Chemical 
 Co.), Telone® (Dow Chemical Co.), and 
 Vidden-D® (Dow), a formulation simi- 
 lar to D-D®. 
 
 Current recommendations (published 
 in the Pest and Disease Control Program 
 for Grapes, University of California Ex- 
 periment Station and Extension Service) 
 for the use of D-D®, Vidden-D® and 
 Telone® suggest the use of D-D® or Vid- 
 den-D® at 60-170 gallons per acre or 
 Telone® at 60-137.5 gallons per acre in 
 old vineyard and orchard soils. In land 
 previously used only for annual crops 
 these recommendations suggest D-D®, 
 Vidden-D® and Telone® at 40 to 60 gal- 
 lons per acre. 
 
 These treatments have produced re- 
 markably stronger vine growth in treated 
 soil as compared to untreated soil. How- 
 ever, a significant population of nema- 
 todes invariably survives these treatments 
 and often increases again within a few 
 years to damaging numbers so that much 
 of the advantage of treatment is lost. 
 
 Recent experiments on control of dag- 
 ger nematode and fanleaf virus have 
 shown excellent results using high dosages 
 of 1,3-D (250 gallon per acre) in a split 
 application (200 gallons at 30 inches * 
 depth on 2-foot spacing plus 50 gallons 
 at 8 to 10 inches depth on 1-foot spacing) . 
 These results have been successful enough 
 to warrant recommendation of this treat- 
 
 [ 14 
 
merit (Pest and Disease Control Program 
 for Grapes, University of California Ex- 
 periment Station and Extension Service) . 
 
 Experiments now are underway to test 
 this treatment on root knot and other 
 nematode prohlems in the lighter sandy 
 soils of the interior valley. There is a need 
 to know if this treatment will protect 
 vines for a significantly longer time, es- 
 pecially during the early critical years 
 when the plants are becoming established. 
 The success of such an expensive treat- 
 ment can only be determined by several 
 years of yield records comparing various 
 dosage levels of the fumigants. 
 
 In any soil fumigation, it is important 
 to seal the soil immediately after treat- 
 ment with a ring roller, springtooth har- 
 row, or heavy drag. Then leave the soil 
 undisturbed until shortly before planting. 
 A waiting period between treatment and 
 planting of at least one week for every 
 10 gallons of fumigant is necessary in 
 light soils. Heavier soils require longer 
 intervals before planting. Longer periods 
 also are required if soil temperature drops 
 significantly or if rains saturate the soil 
 following treatment. Tilling treated soils 
 or digging planting holes a few days be- 
 fore planting hastens aeration in these 
 areas. 
 
 Methyl bromide (CH 3 Br) is a liquid 
 1 under pressure which becomes a gas at 
 normal pressures. It has been used for 
 many years for soil treatment in straw- 
 berry fields and plant nurseries for con- 
 trol of many kinds of organisms, includ- 
 ing weeds, fungi, and nematodes. When 
 methyl bromide is applied, the soil must 
 be covered at time of treatment with a 
 gas-proof tarpaulin such as polyethylene. 
 Rates of 250 to 400 pounds per acre of 
 methyl bromide have been used, usually 
 mixed with chloropicrin. 
 
 In recent years CH 3 Br has been used 
 for control of oak root fungus before 
 planting grapes and is being tested for 
 control of the dagger nematode-fanleaf 
 virus complex. This material is being 
 tested currently for control of root knot 
 
 and other nematodes along with the 1,3-D 
 trials as described above. As with the 
 1,3-D treatments, recent research with 
 methyl bromide indicates that deeper ap- 
 plication must be used to obtain satisfac- 
 tory nematode control. Application depths 
 of 2 to 3 feet have been promising. 
 
 Until further information is developed 
 the use of methyl bromide for nematode 
 control must be considered experimental. 
 
 Treatment of established vines 
 
 Many vineyards suffer decline and re- 
 duced productivity but nevertheless pro- 
 duce sufficiently so that replanting is not 
 considered economic. A treatment of such 
 established vines would be the most prac- 
 tical solution. A chemical for use in side- 
 dressing treatment of growing vines 
 should be nematicidal at economically 
 practical rates and low in phytotoxicity 
 at those rates. 
 
 DBCP meets these requirements at 
 least in part. It is highly nematicidal at 
 rates as low as % gallon per acre. Also 
 it can be used safely around many kinds 
 of plants, particularly woody perennial 
 types, at rates as high as 5 gallons per 
 acre without plant injury. 
 
 DBCP can be applied either by soil in- 
 jection or in irrigation water. Soil injec- 
 tion or "side-dressing" usually is made 
 with a formulation of 50 to 75 per cent 
 (by volume) active ingredient diluted 
 with "paint thinner" or other similar ma- 
 terials. Applications in irrigation water 
 are made with emulsifiable concentrates. 
 
 University of California field trials 
 (in grape) have given most consistent 
 production increases when DBCP was ap- 
 plied in water in flood treatments 
 (basins) wetting the soil to 4 to 6 feet. 
 Results of soil injection (chisel) trials 
 have been inconsistent and have given 
 increased yields only in a few cases. 
 Chisel applications also produce (1) root 
 damage, (2) difficulty in treating closer 
 than 15 to 18 inches of the vine row, 
 thus leaving an untreated strip of l 1 /? 
 to 3 feet down the row, and (3) dam- 
 
 [15 
 
age to cane growth during application. 
 ( lanes also may be a hazard to the opera- 
 tor, unless treatment is made either after 
 pruning or before vine growth begins. 
 
 Sprinkler applications of DBCP are at- 
 tractive t<> growers and have resulted in 
 improved growth and yields in a few 
 cases; however, much of the chemical is 
 lost to the atmosphere during application. 
 The amount of loss apparently depends on 
 atmospheric factors such as temperature 
 and movement of air. These losses cannot 
 be accurately predicted to permit recom- 
 mendations for this method of applica- 
 tion. 
 
 I se of DBCP in flood irrigation treat- 
 ments of grapes has given the most con- 
 sistent results when ectoparasitic nema- 
 todes such as the dagger nematodes were 
 the principal problem. Only a few trials 
 for control of endoparasitic nematodes, 
 such as the root knot nematodes, have 
 been successful. Growers are urged to 
 include untreated areas for comparison 
 with treated areas and to make careful 
 comparison of yields between these areas 
 to determine the economic value of treat- 
 ment. 
 
 DBCP should be used at the rate of 2 
 gallons active ingredient (i.e., 4 gallons 
 50 per cent emulsifiable formulation con- 
 taining 8.6 pounds DBCP per gallon) per 
 acre applied in irrigation water as a post- 
 harvest treatment. Sufficient water should 
 be used to penetrate 4 to 6 feet in depth 
 and the material metered into the water 
 throughout the irrigation. 
 
 The flooding method, however, is lim- 
 ited by the following requirements: 
 
 1. Leveled land. 
 
 2. Equipment to develop borders. 
 
 3. Labor to manage water and main- 
 tain borders during applications. 
 
 Offsetting these limitations are the ad- 
 vantages of treatment of all of the soil 
 area and more 1 uniform distribution of 
 DBCP. 
 
 Some questions about the use of DBCP 
 in vineyards remain to be clarified: (1) 
 Since the most favorable yield responses 
 
 have followed treatments of vines grow- 
 ing in sandy soils, can similar responses 
 be obtained in heavier loam or clay type 
 soils? (2) What is the most favorable 
 timing and rate of application: single ap- 
 plications up to 2V2 gallons per acre of 
 DBCP. repeated lower rates up to 1 gal- 
 lon per acre annuallly, or up to V12 gallon 
 per acre applied three or four times in 
 one season? (3) What is the amount of 
 material lost to the atmosphere during 
 application in water either by flooding or 
 by sprinkler? (4) Can responses be pre- 
 dicted on the basis of nematode species 
 involved? Of population levels? 
 
 Cultural practices and soil 
 preparation 
 
 The roots of woody plants including grape 
 may remain alive in the soil for a long 
 time after such plants have been removed. 
 These roots provide food for plant-para- 
 sitic nematodes and protect endoparasitic 
 types against chemical treatment. 
 
 Allow at least two years after removal 
 of a vineyard or orchard before treating 
 the soil and setting out new plants. When 
 old vines are removed, cut them deeply 
 enough to remove all crowns and prevent 
 suckering. During the two-year rotation 
 period, avoid deep-rooted crops, such as 
 cotton, and highly susceptible crops, such 
 as tomato and potato, which could present 
 a problem of removing crop debris be- 
 fore treatment or would maintain or build 
 up nematode populations. Always allow 
 sufficient time, even after removal of an- 
 nual crops, to permit roots to decay so 
 nematodes are exposed to the action of 
 soil fumigants. Cotton presents a particu- 
 lar problem because this crop is removed 
 late in the fall and its roots do not decay 
 as rapidly as those of fleshy-rooted plants 
 removed earlier in the season. If you have 
 doubt that roots have decayed sufficiently, 
 delay treatment, or use rates of materials 
 suggested following the removal of trees 
 and vines. 
 
 Shortly before treatment the soil should 
 be subsoiled to a depth of 3 feet in at least 
 
 [16 
 
two directions to break up any plow sole 
 or shallow hard pan. Then disc and har- 
 row the soil until tilth approximates a 
 seedbed condition. Soil temperature at the 
 time of treatment should be 50 to 85°F 
 at a 6-inch depth. 
 
 When 1,3-D is used, soil moisture gen- 
 erally should be near field capacity in 
 sandy soils and 50 to 75 per cent of field 
 capacity in heavy soils. (However, some 
 trials with 1,3-D at high rates have given 
 excellent control in dry sandy soils.) The 
 use of methyl bromide requires that soil 
 moisture be as low as possible. Sudan 
 grass or safflower should be grown dur- 
 ing the summer preceding a late summer 
 or fall treatment to dry the soil out as 
 completely as possible. Following this, the 
 soil should be ripped and tilled as for 
 1,3-D treatment. 
 
 Geographical influence on control: 
 
 In the San Joaquin Valley and Southern 
 California interior valleys, endoparastic 
 nematodes are the most important nema- 
 tode parasites of grape. Root knot nema- 
 todes predominate, but root lesion nema- 
 todes also are common in the San Joaquin 
 Valley and may occur in the same vine- 
 yards. Adequate crop rotation before 
 treatment and replanting is particularly 
 important in these areas, because the 
 nematodes most commonly found are en- 
 doparasitic, and the woody roots of vines 
 or trees may persist and harbor and pro- 
 tect nematodes for a long time. 
 
 Soils of the interior valleys are often 
 light-textured sandy types, and irrigation 
 water is generally available, even though 
 not always adequate. Moisture necessary 
 for good land preparation and treatment 
 usually can be provided during the favor- 
 able fall period. 
 
 In the central and northern California 
 coastal valleys, endoparasitic nematodes 
 ordinarily are a minor problem in the 
 non-irrigated areaswherethe heavier min- 
 eral-type soils have a high water-holding 
 capacity. In these areas the most common 
 nematodes found on grape are ectopara- 
 
 sites, especially dagger nematodes, al- 
 though ring nematodes and pin nema- 
 todes also are found. 
 
 Irrigation water is not generally avail- 
 able, and proper land preparation may be 
 dependent on rainfall, limiting the period 
 when soil treatment can be made. When 
 land preparation and treatment cannot be 
 made until spring, cooler soil temperature 
 and the heavier soil types may delay 
 planting beyond a desirable planting date. 
 
 Management practices 
 
 New vines require special attention to 
 attain maximum vigor and growth in 
 the early years after planting. Adequate 
 water and fertilization, careful pest con- 
 trol, and pruning to the vigor of indivi- 
 dual vines all will contribute to the basic 
 strength of the vines. 
 
 Clean nematode-free stock should be 
 insured by planting cuttings taken from 
 canes, the desired portion of which were 
 not in contact with the soil. To establish 
 a vineyard with cuttings, considerable ex- 
 perience is needed to care for vines 
 planted over a relatively large area. In 
 general, we would recommend the plant- 
 ing of strong rootings to best insure a 
 good stand of vines. 
 
 Hot water treaments for nematode con- 
 trol (or phylloxera) are necessary if root- 
 ings did not come from a fumigated nur- 
 sery site, if there is any doubt about the 
 cleanliness of the rootings, or if they are 
 lightly infested with nematodes but other- 
 wise have made strong growth. 
 
 Hot water treatment should be given 
 only to strong rootings which are com- 
 pletely dormant. Following washing, trim- 
 ming and bundling, submerge the vines 
 in water heated to 125°F and hold there 
 for exactly five minutes. Accurate timing 
 and uniform temperature are important 
 for good control and vine safety. Cool the 
 rootings immediately following treatment 
 and protect them from drying out. They 
 may be planted directly or heeled-in in a 
 nematode-free medium such as wood 
 shavings. A more complete discussion of 
 
 [17] 
 
these procedures is available from your 
 local farm advisor in the U.C. Extension 
 sheet OSA #48, "Hot water dip for nem- 
 atode control on grape rootings." 
 
 Care of young vines often determines 
 the success of a commercial vineyard. 
 Good cultural practices include: 1. Care- 
 ful pruning of vines as they come into 
 bearing. Overcropping, an imbalance 
 of fruit with vine capacity, can easily re- 
 sult from leaving too many canes at the 
 second and third winter's pruning of the 
 Thompson Seedless variety, for example. 
 Wine grape varieties that are trained to 
 a bilateral cordon are readily overcropped 
 when too many spurs are left on the 
 quickly established framework. In both 
 cases, early removal of the excess number 
 of bunches by thinning effectively pre- 
 vents fruit overload. 
 
 2. Irrigation practice designed to main- 
 tain a supply of available moisture in the 
 root zone during the growing season. Do 
 not, however, stimulate late growth which 
 deters good wood maturity. 
 
 3. Pests and disease control, such as for 
 Pacific mites and powdery mildew, which 
 can materially damage leaves and hence 
 their ability to function and elaborate the 
 carbohydrate materials needed for vine 
 growth and fruit development. 
 
 4. Fertilization of sandy soils in which 
 root knot nematodes are generally a prob- 
 lem. Nitrogen, the element usually needed, 
 should be applied in the dormant season. 
 
 5. The date of proper timing for harvest. 
 Since the major storage of carbohydrate 
 reserves in the vine does not occur until 
 after the fruit is picked, the harvest date 
 should not be delayed. An inadequate 
 storage of reserves results in weakened 
 vines. The preplant fumigation gives the 
 vine an opportunity to become estab- 
 lished. Good growing practices, however, 
 are essential to maintain healthy, vigor- 
 ous vines that can bear good crops of 
 good-quality fruit each year. 
 
 Nematode-resistant rootstocks 
 
 Several species of grapes native to the 
 
 [18 
 
 central southern part of the United States 
 have inherent resistance or tolerance to 
 nematodes. Field trials in California with 
 hybrids or varieties of these species have 
 demonstrated their value as rootstocks in 
 commercial vineyards. 
 
 The proper choice of the stock best 
 suited for a given variety and vineyard 
 situation is very important. Nematode-re- 
 sistant stocks differ considerably in vigor 
 and in their effects on fruit quality and 
 vine behavior. The most vigorous stocks. 
 Dogridge and Salt Creek, are recom- 
 mended only for very sandy soils with 
 a low fertility and water-holding capacity. 
 The less vigorous stocks should be planted 
 in the more favored vineyard soils. 
 
 Wine and raisin grape varieties have 
 been more readily adapted to the use of 
 nematode-rCsistant rootstocks than those 
 of table grapes, since appearance of the 
 mature fruit is of minor importance. Re- 
 sults with table varieties have been vari- 
 able, even though many successful table 
 grape vineyards on rootstocks may be 
 found. Without careful vineyard manage- 
 ment, the color of red table varieties, for 
 example, may be duller and darker and 
 the bunches may have a poorer set, re- 
 sulting in a straggly appearance. These 
 undesirable results may be minimized by 
 careful management, including pruning, 
 water and fertilizer management, and the 
 use of zinc applications. 
 
 A brief summary of some of the char- 
 acteristics and behavior of the rootstocks 
 currently recommended for use in Cali- 
 fornia vineyards is given in table 3. The 
 first four stocks have resistance or toler- 
 ance to nematodes and are recommended 
 for use in the San Joaquin Valley and in 
 the interior valleys of southern California. 
 The remaining stocks, St. George and 
 A x R 1, while they do not possess nema- 
 tode resistance, are resistant to phylloxera 
 and are the stocks of choice for the coastal 
 valley counties. Rootstocks with dual re- 
 sistance to these two pests are urgently 
 needed. 
 
 Cultural practices where rootstocks are 
 
 ] 
 
Table 3 
 
 SUMMARY OF THE CHARACTERISTICS OF GRAPE ROOTSTOCKS CURRENTLY 
 RECOMMENDED FOR CALIFORNIA 
 
 
 Rating 
 
 
 Rootstock 
 
 Nematode susceptibility* 
 
 Phylloxera 
 suscepti- 
 bility* 
 
 Performance! 
 
 Remarks 
 
 
 Root 
 knot 
 
 Lesion 
 
 Dagger 
 
 Table 
 
 Wine, 
 raisin 
 
 
 Dogridge, 
 Vitis champini 
 
 1 
 
 1 
 
 2 
 
 2 
 
 V 
 
 G 
 
 Very vigorous. For heavy pro- 
 ducing wine or raisin varieties 
 grown on very sandy soils of low 
 fertility where nematode damage 
 is usually severe. 
 
 Salt Creek 
 (Ramsey), 
 V. champini 
 
 1 
 
 1 
 
 2 
 
 2 
 
 V 
 
 G 
 
 Very vigorous. Excessive growth 
 more easily controlled by cultural 
 practice than with Dogridge. Use 
 in same situations as Dogridge. 
 
 Harmony 
 (1613 sdlg. X 
 Dogridge sdlg.) 
 
 n 
 
 2 
 
 1 
 
 1 
 
 V-G 
 
 G 
 
 More vigorous than 1613, but not 
 as vigorous as Dogridge or Salt 
 Creek. Well suited to all but very 
 sandy soils, and particularly 
 suited for raisin or wine grape 
 production. 
 
 1613, Solonis X 
 Othello 
 
 it 
 
 3 
 
 1 
 
 2 
 
 V-G 
 
 G§ 
 
 Vigorous. Well adapted to fertile 
 loamy sand to sandy loam soils 
 of the San Joaquin Valley. 
 
 St. George, 
 V. rupestris 
 
 3 
 
 3 
 
 3 
 
 1 
 
 V 
 
 G§ 
 
 Vigorous. Susceptible to nema- 
 todes. Well adapted to shallow 
 or nonirrigated soils in the coastal 
 valley areas. 
 
 AXR#1 
 (Aramon X 
 Rupestris, 
 Ganzin No. 1) 
 
 3 
 
 3 
 
 3 
 
 1 
 
 V 
 
 G§ 
 
 Vigorous. Susceptible to nema- 
 todes. Best performance on the 
 fertile valley soils in coastal 
 counties. 
 
 * 1 = low; 2 = intermediate; 3 = high. 
 
 t V = variable; G = good. 
 
 t Some strains in local areas may be damaging. 
 
 § Wine varieties only. 
 
 used will probably have to be adjusted for 
 growth will tend to in- 
 owth becomes overly 
 
 ■ 
 
 ■ 
 
 o leave more fruiting 
 duce or even eliminate 
 Dn, and reduce irriga- 
 te summer. Such vines 
 zinc deficiency, which 
 clusters and lighter 
 ;ncy can be remedied 
 ieties by daubing the 
 id with a zinc sulfate 
 
 rootstock vines care- 
 worn from virus dis- 
 
 19 
 
 eases. Rootstock mother vines may be 
 symptomless carriers of virus diseases, 
 which have little effect on the growth 
 and development of the rootstocks but 
 which may drastically affect the crop and 
 vigor of the scion variety after budding 
 or grafting. Certified planting stock is the 
 most reliable source of clean rootstock 
 vines and is obtainable from participants 
 in the Grapevine Registration and Cer- 
 tification Program administered by the 
 California Department of Agriculture. 
 
 Additional costs are encountered where 
 rootstocks are used — for rootstock vines, 
 in disbudding, in budding or grafting 
 
 ] 
 
and U nv-up, and in suckering. These 
 costs Ti y be easily offset by the develop- 
 ment of a vineyard with "built-in" pro- 
 tection, one that will have a normal eco- 
 nomic life without further investment. In 
 
 very sandy s >. re nematode i' 
 
 tions are heavy, it may be imposs 
 grow grapevines without the use ol 
 tode-resistant rootstocks. 
 
 To simplify this information, it is sometimes necessary to use trade namt. 
 products or equipment. No endorsement of named products is intended nor is i 
 cism implied of similar products not mentioned. 
 
 r 
 
 12%m-ll,'73(R1649L,)PAD