Prepared: December 15, 1999
Grapes are grown in all areas of California with the exception of the high country. The University of California identifies six regions for grape production within the state:
1) The northern San Joaquin Valley: San Joaquin, Calaveras, Amador, Sacramento, Merced, and Stanislaus Counties; 2) The Southern San Joaquin Valley: Fresno, Kings, Tulare, Kern, and Madera Counties.; 3) The Coachella Valley: The Coachella regions of Riverside, Imperial, and San Bernadino Counties; 4) North Coast: Lake, Mendocino, Napa, and Sonoma Counties; 5) Central Coast: Alameda, Monterey, San Luis Obispo, Santa Barbara, San Benito, Santa Cruz, and Santa Clara Counties and 6) South Coast: San Diego, and Western Riverside counties. Each region has distinct climatic and geologic differences that lead to different cultural and pest management practices.
Production of table grapes is largely centered in the Southern San Joaquin Valley region, although a significant portion of production comes from the Coachella Valley region (5). The remaining regions account for less than 1% of the state's production.
Cultural practices for grape production vary widely, depending on the intended use of the crop (i.e., table, wine, or raisin), the growing region, and the management preferences of the grower. Pest management priorities are also impacted by the intended use where, for example, control of pests that cause cosmetic damage to the fruit can be much more important in the production of table grapes than in wine and raisin grapes.
Table Grape Varieties and Production. There are over 50 varieties of table grapes grown in California, 18 of which are considered major varieties. Thompson Seedless and Flame Seedless are the two dominant varieties produced in California, followed by Red Globe, Ruby Seedless, Crimson Seedless and Perlette (5,8). Table grape production primarily occurs in the warm, dry inland valleys, with most of the production being in the Southern San Joaquin Valley region (Fresno, Kern, Kings, Madera, and Tulare Counties) and Coachella Valley region. Sandy loam to clay loam soils are preferred.
General Practices. Vines are pruned during the dormant season and, for cane-pruned varieties, canes are tied to the trellis wires before spring growth starts. Pre-emergent herbicide applications are applied during the dormant season, and most contact herbicide applications are made from fall through late spring. Nitrogen and zinc fertilizers are applied in the spring, with potassium and boron fertilizers applied in fall through winter. Drip irrigation has recently become the preferred method of irrigation, though furrow irrigation still dominates in the southern San Joaquin Valley. Other production practices include canopy management (i.e., vine training, shoot positioning, leaf pulling, and trunk suckering), vineyard floor management (i.e., cover cropping, cultivation and mowing), pest management, and harvesting. Cultural practices such as irrigation and floor management can play a role in pest management. Once harvested, the grapes are picked, field packed, kept in cold storage, fumigated with SO2, and transported to markets.
Pests Of California Table Grapes
The following summaries of grape pests and their management are based, to a large extent, on the summaries compiled and distributed by the University of California Integrated Pest Management Project (UC-IPM Project)(2,24,38,48). These guidelines were authored by many different specialists and advisors from the University of California's Cooperative Extension. We wish to acknowledge this contribution.
The following pest management summaries are also based on publications and documentation from the UC Division of Agriculture and Natural Resources, the UC Sustainable Agriculture Research and Education Program, California's Department of Pesticide Regulation, the Lodi-Woodbridge Winegrape Commission, the Central Coast Vineyard Team, and other sources of documentation on grape pest management. The summaries are also based on extensive comments and suggestions from individuals from the agricultural community and members of the California Grape Advisory Team, who include: Jenny Broome, Associate Director, UC SAREP; Paul (Augie) Feder, Agricultural Policy Specialist, U.S. EPA Region 9; Karen Ross, President, California Association of Winegrape Growers (CAWG); Joe Kretsch, Project Coordinator, Sun-Maid Raisin Best Management Practices Program; Rick Melnicoe, CAPIAP; Linda Herbst, CAPIAP; Charlie Goodman, Research Manager, Office of Pesticide Analysis and Consultation, California Department of Food and Agriculture (CDFA); John Steggall, Office of Pesticide Consultation and Analysis, CDFA; Mike Vail, Viticulturist, Vino Farms, Inc.; Frank Zalom, Director, UC Statewide IPM Program; Jennifer Curtis, Environmental Policy Consultant to the Natural Resources Defense Council (NRDC); Richard Matoian, California Grape and Tree Fruit League. Special thanks to the following individuals for their helpful reviews of sections in their area of expertise: Drs. Jeffrey Granett and Amir Omer (phylloxera), Dr. Kent Daane (mealybugs), Dr. Alex (Sandy) Purcell (sharpshooters), Dr. Mike McKenry (nematodes), Dr. Doug Gubler (powdery mildew, measles) and Dr. Tim Prather (weeds).
The grape pests in this document are separated into major insect and mite pests, minor insect pests, nematodes, major and minor diseases, weeds, and vertebrate pests. The order of each pest is presented based on its importance to the pest management system, in terms of pesticide use, control efforts, or actual or potential damage.
Except where otherwise noted, the pesticide use data presented in the following summaries are based on the Department of Pesticide Regulation's (DPR) 1997 Pesticide Use Report (9).
Variegated leafhopper: Erythroneura variabilis
Grape leafhopper: Erythroneura elegantula
Damage. Leafhoppers (Homoptera: Cicadellidae) are major pests of grapes throughout California. The grape leafhopper is a major pest of grapes north of the Tehachapi Mountains, especially in the San Joaquin (primarily Northern San Joaquin Valley Region), Sacramento Valley, and Napa Valleys (North Coast Region) (71). It is occasionally a problem in coastal valleys (Central and South Coast Regions). The variegated leafhopper is a major pest of grapes in Southern California (Southern San Joaquin Valley, South Coast, and Coachella Valley regions). Variegated leafhopper is a major pest as far north as San Joaquin County (Northern San Joaquin Valley region). Actual pest damage varies according to location of the vineyard, variety, plant vigor, market use of the variety, and season. Substantial infestations result in loss of yield and/or quality. Large numbers of flying adults can cause significant worker annoyance, which can lower productivity.
As leafhoppers feed on leaves and injury increases, photosynthetic activity decreases. Heavily damaged leaves lose their green color, dry up, and may fall off the vine. This can result in fruit sunburn and can weaken the vine for the following season. Feeding can also delay berry sugar accumulation and leafhopper production of "honeydew" (excess carbohydrates) can result in spotting of fruit (mold which grows on the honeydew). Spotting is a major economic concern for table grapes.
Life History of the Pest. Leafhoppers overwinter as adults, and are found in spring on newly emerged grape leaf tissue, cover crops and weeds. Eggs of the first brood are laid in leaf epidermal tissue in April and May. Both adults and nymphs feed on leaves by puncturing leaf cells and sucking out the contents.
Monitoring. Growers and pest control advisors monitor for leafhoppers by counting the number of nymphs per leaf and by visual assessment of leaf damage. The most critical period is during the second leafhopper generation, because it is then that leafhoppers are feeding primarily on photosynthetically active foliage. Economic loss probably does not occur until at least 20% of the photosynthetically active leaf area is damaged, which is roughly equivalent to 15-20 nymphs per leaf for Thompson Seedless in the San Joaquin Valley (71).
Several natural enemies of the grape leafhopper are considered important in biological control strategies. Use of broad spectrum insecticides can negatively affect these natural enemies and may exacerbate a leafhopper problem.
Most table grape vineyards, especially those planted to white varieties, are treated for leafhoppers at least once a year. In some cases, chemical treatment of leafhoppers may exacerbate a mite problem if predatory mites are disrupted. Methomyl, carbaryl and dimethoate, all of which are registered for control of leafhoppers, are highly toxic to predatory mites. At present, imidacloprid is an extremely effective and long lasting material for leafhoppers and has minimal negative effects on natural enemies (22).
Vine Mealybug: Planococcus ficus
Damage. Mealybugs (Homoptera: Pseudococcidae) are a major pest of table grapes in California. Mealybugs can damage grapes by feeding on leaves and by contaminating clusters with honeydew, which supports the growth of black sooty mold (28). In addition, all mealybugs tested have been shown to vector leafroll viruses. Feeding by mealybugs can be severe enough to stunt vine growth, but this only commonly occurs with obscure and vine mealybugs. Cluster contamination by mealybugs is related to variety and pruning method. It can be worse on spur pruned varieties and on varieties that produce a high percentage of clusters close to the base of the shoot, resulting in clusters that touch old wood. Mealybugs also take advantage of tight clustered varieties, where they are better hidden. The primary mealybug pest of table grapes has until recently been the grape mealybug, but there is increasing concern about the vine mealybug. The vine mealybug hails from the Mediterranean region, and was first found in the Coachella Valley in 1994 (1). Since then it has infested virtually all acreage in the Coachella region and has become a major pest there. In 1998 it was also discovered in Kern and Fresno Counties (Southern San Joaquin Valley). The vine mealybug can potentially cause far greater damage than the other vineyard mealybugs, as it feeds on leaves, shoots and roots and can severely stunt vine growth. Vine mealybug can also contaminate grape bunches with honeydew, producing far greater amounts of honeydew than the grape mealybug, and may have up to 8 generations per year in the San Joaquin Valley (compare with 2-4 for the grape mealybug).
Life History of the Pest. Mealybugs overwinter as adults, eggs (in white, cottony egg sacs) and first instar crawlers. Most of the overwintering population is found underneath the bark, quite often on the upper trunk sections, cordons and spurs (29). Crawlers emerge in late winter and make their way to buds, where they begin feeding once bud break occurs. Adult females return to the bark to lay eggs of the next generation, which, when hatched, colonize grape bunches.
Monitoring. Growers and PCAs can most easily monitor for the presence of mealybugs in the winter. Just prior to budbreak the crawlers will be active, and their numbers can be estimated by recording mealybug presence under bark on spurs. Double sided tape wrapped around spurs can be used to trap crawlers, but this is a less reliable method than direct counts. However, there are no established treatment thresholds for these methods. Early summer infestation can be estimated by counting mealybugs on spurs (3,29), and late-season evaluation consists of analyzing clusters which are not free hanging (touching the cordon, trunk or stake) and recording by presence/absence. There are no reliable methods of monitoring for parasitism.
Natural enemies can keep mealybugs under control in some cases, but mealybug parasites are very sensitive to broad spectrum insecticides. It is generally recommended that if chemical treatment is necessary, some areas of the vineyard should be left untreated as a refuge for parasite populations. Controlling ants will also help parasites control mealybugs.
Willamette mite: Eotetranychus willamette
Pacific mite: Tetranychus pacificus
Twospotted mite: Tetranychus urticae
Damage. Webspinning spider mites (Acari: Tetranychidae) can be a major pest of table grapes, depending largely on the soil type in which they are grown (27). The Pacific mite is the most important mite species on sandy, alkali, salty or sodic soils of the San Joaquin Valley. Pacific mite damage begins as yellow spots, and as damage progresses, these spots may turn brown (necrotic). High populations may cause leaf burning, which can decrease photosynthesis and accumulation of vine energy reserves. Pacific mite is not a problem on the heavier soils along the east side of the valley, but Willamette mite can cause damage in these areas. Willamette mite feeding causes foliage to turn yellowish bronze or red (depending upon the variety), but usually no burn occurs unless vines are weak.
Life History of the Pest. Although it can cause damage early in the season, Pacific mite generally prefers the hotter, dryer part of the season (27). Willamette mite is an early season mite in the Southern San Joaquin Valley, where it prefers the cooler parts of the plant and is found mostly on the shady parts of the vine. On east-side valley acreage, Willamette mite can be active throughout the season and can cause significant damage. The twospotted mite, Tetranychus urticae, is only occasionally found on grapes in California and rarely causes damage.
Monitoring. Monitoring is conducted to determine the intensity of the mite population in relation to the treatment threshold. Typically, monitoring for Pacific mite is accomplished by a binomial (presence-absence) sampling method, whereby infestation is estimated by the percentage of leaves which have 1 or more mites. Treatment is recommended if 50% or more of the leaves are infested and there are no predatory mites present (27). There are no monitoring guidelines available for Willamette mite.
Chemical treatments must not be disruptive to predators of spider mites.
Grape thrips: Drepanothrips reuteri
Western flower thrips: Frankliniella occidentalis
Damage. Grape thrips and western flower thrips (Thysanoptera: Thripidae) are the primary species that can cause damage on grapes (44). Damage from both species occurs from feeding on actively growing shoot tips, which can distort leaves and stunt shoots. Western flower thrips shoot damage can occur in spring and summer, whereas grape thrips damage occurs in mid-summer. In the northern San Joaquin Valley, North Coast and Central Coast, feeding by western flower thrips occasionally causes enough damage to require treatment, but damage by grape thrips is rare because there is usually sufficient foliage by the time their populations peak. Damage can also occur by grape thrips feeding on berries, which may scar and crack.
Life History of the Pest. Western flower thrips overwinter as adults and nymphs. They will feed on a variety of plant parts, adults feeding on pollen, and nymphs feeding on shoot tissue. Eggs are laid in soft tissues, especially of young flowers. Western flower thrips populations peak in May, coinciding with grape bloom.. Grape thrips overwinter as virgin females, and the first generation in spring is produced asexually. They feed on grapes, and have also been found on poison oak (Rhus diversiloba). Populations reach their greatest numbers in July.
Monitoring. Visual inspection of shoots in spring is the only practical method of monitoring for western flower thrips, but no treatment thresholds have been established. No specific monitoring guidelines have been developed for grape thrips on shoot tips.
Little is known about natural control of thrips in vineyards. An important thrips predator is the minute pirate bug, but its numbers are usually quite low on grapes.
Chemical treatment may be necessary in spring if western flower thrips populations are high enough to stunt shoots.
Damage. The omnivorous leafroller (OLR) is a moth whose larval stage can cause serious damage in the Northern and Southern San Joaquin Valley regions (16). It is a major pest of table grapes. It feeds on leaves, flowers, and developing berries. Damage to post-veraison berries allow rot organisms to enter the fruit.
Life History of the Pest. OLR larvae overwinter in old grape clusters (mummies) and vineyard weeds. In spring, the larvae complete their development and moths emerge and lay shingle-like egg masses on grape leaves. After about 5 days these eggs hatch, and larvae web together leaves or cluster parts to form a nest in which they feed.
Monitoring. Growers and PCAs monitor for OLR by examining grape bunches. Critical periods for monitoring are during the critical treatment window for each of the first two generations. Pheromone traps are used to catch male moths and provide the bio-fix dates. 700-900 degree days past biofix is the recommended treatment window for OLR (17).
Because the most widely used insecticides for OLR (cryolite and B.t., see below) are stomach poisons which need to be eaten by OLR larvae to be effective, spray timing and coverage are extremely important. Most table grape growers treat for first brood OLR with cryolite, but are reluctant to treat later in the season (for second brood) because of concerns that it might burn leaves and spot berries, even though recent research indicates that in some cases second brood treatments may be more effective (18). There are many cases in which OLR was not present in the vineyard in spring, but migrated in later in the season (M.J. Costello, personal observation). In these cases, broad spectrum OPs or carbamates are used for late-season control.
Damage. Grape phylloxera is an aphid-like insect (Homoptera: Phylloxeridae) which damages grapevines by feeding on roots, either on growing rootlets, which then swell and turn yellowish, or on larger roots, which also swell and may decay. Feeding injury causes vines to become stunted, produce less fruit and eventually die. Recent work suggest that several soil borne fungi may play a role in phylloxera damage by infecting roots at sites of phylloxera feeding (33,56). Although phylloxera is present in the heavier soils of the San Joaquin Valley (mostly the foothill areas), damage is not as severe as in the coastal areas, possibly because soils are deeper and water more plentiful, or because phylloxera do not do well in the warm summer temperatures of the valley. Phylloxera is not a pest on sandy soils.
Life History of the Pest. Phylloxera adults are wingless and reproduce without males, laying up to several hundred eggs per female (32). Eggs hatch in about a week into nymphs which grow and molt four times to become adults. Grape phylloxera overwinter as small nymphs on roots, and in spring, they start feeding and developing. Once established on a root, phylloxera feed in groups. Infested vineyard areas expand concentrically, and may do so rapidly at a rate of two- to four-fold a year. Satellite infestations frequently establish downwind or along water channels from larger infested areas. In fall when soil temperatures decrease, all life stages die except the small nymphs (57). There are three to five generations each year.
Monitoring. Initial infestations of grape phylloxera appear as a few weakened vines. Therefore, monitoring vines in an area of the vineyard that has consistently displayed weaker growth is necessary. Aerial photography can be useful in detecting weak spots in vineyards (45).
There are no specific biological controls targeting grape phylloxera.
A pesticide treatment will not eradicate phylloxera populations because of the difficulties in penetrating the heavy soils that this pest prefers. Populations may rebound rapidly after a chemical treatment, and it may be difficult or impossible to stop overall vine decline(68).
Green sharpshooter: Draeculacephala minerva
Red-headed sharpshooter: Carneocephala fulgida
Glassy-winged sharpshooter:Homalodisca coagulata
Damage. Sharpshooters vector the bacterium Xylella fastidiosa, which causes Pierce's disease (see section on disease) in grapes, one of the few grapevine diseases that can kill vines (31). Sharpshooters (Homoptera: Cicadellidae) are leafhoppers, but belong to a subfamily that feeds on the water conducting vessels of the plant (the xylem) (61). Until recently, the green sharpshooter (GSS) and the red-headed sharpshooter (RHSS) are the primary vectors in the South and North San Joaquin Valley regions. However, in 1998, the glassy-winged sharpshooter (GWSS) was detected in the Southern San Joaquin Valley, and in 1999 it was found in the Northern San Joaquin Valley. GWSS invaded California from the southeastern US, and was first found on eucalyptus in Ventura County in 1990 (60). GWSS is a large insect (10-12 mm or 0.5 inch) and a strong flyer, which feeds and reproduces on over 70 species of plants in at least 35 different families. Cultivated host plants include citrus, apricot, grape and eucalyptus, and native host plants include sycamore and oak. It has established high populations in southern California, and has become troublesome on grapes in the Temecula Valley. Because of its strong flying ability, its broad host range and ability to transmit Pierce's Disease (PD), GWSS is potentially a major problem for table grape production. PD is present in Fresno and Madera County and has been detected in the Southern San Joaquin Valley.
Life History of Pest. GSS and RHSS prefer grasses for feeding and breeding, and can often be found in pastures, weedy alfalfa fields, and on roadside weeds. Grapes are only accidental hosts of these grass-feeding sharpshooters. The overwintering adults do not live long, thus it is probably the second generation that migrates to the vineyard. Citrus is a primary overwintering host for GWSS, which can also overwinter in vineyards, feeding on dormant wood. Sharpshooter dispersal and rate of development is temperature dependent.
Monitoring. Sticky traps are not very effective monitoring tools for sharpshooters, because these insects are not attracted to the yellow cards. Sweep nets can be used to monitor populations in non-crop vegetation adjacent to vineyards. Light traps may be more effective monitoring tools.
Few biological control agents have been identified that are specific to sharpshooters. The most common parasitoids of GSS and RHSS are parasitic wasps in the families Mymaridae and Trichogrammatidae that attack eggs. A mymarid egg parasite has been found attacking GWSS.
In the Central Valley, insecticide treatments on border vegetation are of little value overall because overlapping generations result in the continuous presence of eggs inside protective leaf tissues of host plants from February through fall. Sprays are not effective against eggs. Also, there are few chronically affected areas that would require treatment every year.
MINOR INSECT PESTS
Some insect pests are considered minor either because they are restricted to a relatively small region in the state, or because they only occasionally surface at densities high enough to cause damage. Therefore, collective treatment for any given minor pest is minimal. However, the damage that a minor pest can cause in a particular vineyard can be major, resulting in a significant loss to that grower. Often there is a lack of knowledge of cultural and biological controls for minor pests, and as a result, their control is almost entirely chemical dependent.
WESTERN GRAPELEAF SKELETONIZER
Damage. Western grapeleaf skeletonizer (WGLS) (Lepidoptera: Zygaenidae) larvae feed gregariously on lower leaf surfaces, leaving only the veins and upper cuticle, and giving damaged leaves a whitish paper like appearance (65). Maturing larvae completely remove all interveinal tissue, leaving only the larger veins. When abundant, larvae can defoliate vines. If there is no leaf area left, larvae may feed on grape clusters as well. Defoliation can result in sunburn of the fruit and quality loss, as well as reducing reserves for the next year's crop.
Life History of the Pest. WGLS overwinters as a pupa in a dirty, whitish cocoon under the bark. The metallic bluish-black moths emerge in spring and can be seen flying during early morning hours. There are three generations per year in the Central Valley and two generations in the cooler coastal regions. Female moths lay pale yellow or whitish capsule-shaped eggs in clusters on the underside of grape leaves. After hatching, the larvae line up and feed side-by-side on the leaf underside until the early fourth instar stages, and feed in isolation for the remainder of their development. When mature, larvae crawl under the loose bark or under ground litter to pupate.
Monitoring. Because WGLS has become a minor pest since the mid-1990s, formal monitoring for it is rare. Early larval infestations can be detected by the presence of whitish paper-like leaves.
No cultural methods have been identified to control this pest.
Treatments applied for omnivorous leafroller will usually control WGLS early in the season.. If the biological control agents are not present or have been disrupted by broad spectrum insecticides, the amount of leaf damage will increase with each generation.
Variegated Cutworm: Peridroma saucia
Spotted Cutworm: Amathes c-nigrum
Brassy Cutworm: Orthodes rufula
Damage. Feeding on grapevines occurs from bud swell to when shoots are several inches long. Injured buds may fail to develop shoots or clusters and, depending on variety, cause yield reduction, primarily on varieties with non-fruitful secondary buds. Even then there are indications that 25% bud loss can be tolerated. Many varieties of grapes can tolerate a significant amount of damage without any economic loss.
Description of Pest. Cutworms are inconspicuously marked, dull-colored caterpillars. Variegated cutworm is the predominant species in the San Joaquin Valley, the primary location for table grape production, while spotted cutworm is predominant in the north and central coast counties, wine grape regions. In the San Joaquin Valley regions, variegated cutworm larvae do not return to the soil, but rather move under the vine bark. Spotted cutworms routinely remain under grapevine bark in all production areas.
Monitoring. Historical records of cutworm infestations are useful in developing monitoring strategies for individual vineyards because cutworm problems are normally spotty or localized. Growers begin to monitor bud feeding by cutworms during bud swell in early spring. Treatments are typically warranted when disruption happens or damage to the side of the bunch is noted.
Cultural practices have not been demonstrated to successfully control cutworms; however, some practices do affect their population abundance.
No chemicals are highly effective in controlling cutworms, so treatments may not be economically justified. However, hand applied bait applications allow for treatment of only the affected area.
Damage. Grape leaffolder (GLF) (Lepidoptera: Pyralidae) is a pest in the Southern San Joaquin Valley which can cause damage by constructing leaf rolls and feeding within. Damage occurs due to loss of leaf area, and sun exposure from excessive leaf rolling may lead to sunburning. Usually damage occurs only late in the season.
Life History of the Pest. The first moth flight is usually in late March or early April. Eggs are laid on leaves, and after hatching, larvae feed in groups between two webbed leaves for about 2 weeks. Then each larva rolls a leaf edge and feeds from the inside on the leaf edge. Mature larvae construct a separate leaf envelope on the edge of a leaf in which they pupate.
Monitoring. Growers and PCAs may monitor for GLF by counting the number of rolls in a given area. There are no established treatment thresholds.
There are no identified cultural practices for the control of GLF.
Naturally occurring parasites play an important role in keeping grape leaffolder below a level that will cause damage. Several parasites attack GLF.
Treatment of the first generation is rarely needed. Usually first brood control of grape leaf folder is achieved because of spring treatment for OLR (see Omnivorous Leafroller).
FALSE CHINCH BUG
Damage. The false chinch bug (Hemiptera: Lygaeidae) occurs sporadically, but may occasionally cause rapid and serious damage to young vines. They suck plant juices and inject a toxin that causes vines to wilt and turn brown. They are especially damaging to young vineyards. Because of the great number of bugs involved and their toxic injections, all the leaves on border vines can be killed in a few hours.
Life History of the Pest. This pest breeds in great numbers in grass or weedy areas, especially on mustard family members such as London rocket and shepherd's purse, and may migrate en masse into vineyards in late spring when these areas dry up and the pests search for green growth. September and October migrations are also possible.
Monitoring. An effective monitoring program can be undertaken by paying close attention to the types of vegetation within and adjacent to young vineyards, and visually inspecting them for false chinch bug.
No biological controls have been identified for this pest.
If high populations of false chinch bugs are found on weeds at bud swell or after vines leaf out, applications of insecticides to the weeds may be applied. If nymphs are found moving onto vines, spot treatment to both vines and weeds may improve control. Insecticides should be applied in early morning or late evening when the majority of the population is exposed.
GRAPE BUD BEETLE
Damage. The grape bud beetle (Coleoptera: Chrysomelidae) is found in the San Joaquin Valley and the Coachella Valley. Adult beetles cause crop loss by feeding on newly opened buds and eating the bud center, which contains the immature leaves and flower cluster primordia. Once the new shoots are 1 to 1.5 inches long, feeding damage is negligible.
Life History of the Pest. The immature stages (grubs) of the beetle are spent in the soil, where grubs feed on grape roots. Adults may begin emerging from the soil several weeks prior to budbreak, mate, lay eggs under bark, and feed once buds have opened. Beetles are long lived, and their numbers accumulate into the spring. There is one generation per year.
Monitoring. Growers and PCAs may monitor for grape bud beetle to determine if chemical treatment is necessary. Adults come out of daytime hiding places about 1 hour after sundown. Although beetles can be monitored with a flashlight, an ultra-violet lamp is preferred because the beetles naturally fluoresce a bright silvery blue when under UV light.
No cultural practices have been identified to control this pest.
No biological controls have been identified to control this pest.
During budbreak, treatment is recommended when there are one to three beetles per vine and bud damage is noticeable.
Damage. Powdery mildew is the most significant disease affecting grapes in California. The mycelia (fungal strands) penetrate into leaf, stem and berry tissue. Whereas severely affected leaves may have reduced photosynthetic rates, most damage occurs because mildewed berries may be stunted, crack and collapse, and lead to secondary bunch rot. Sugar accumulation may be delayed in severely affected vines. It is estimated that powdery mildew is present in virtually all vineyards each year, the only variable being the severity of the infection between vineyards. Approximately 90% of the grape acreage in California (89% in 1997) is treated for powdery mildew. The non-treated acreage is largely non-bearing acreage.
Description of Symptoms and Disease Cycle. In the Northern San Joaquin Valley, powdery mildew overwinters as ascospores (sexually produced spores) within cleistothecia (fruiting bodies) on the bark, canes and spurs. Ascospores require free moisture to germinate, and are released onto new grape leaves with spring rains or sprinkle irrigation. Mycelial growth takes on a white, web-like appearance. As conidia (asexual spores) are produced, the colony takes on a white, powdery appearance. Optimal temperatures for hyphal growth and conidia production are between 70 and 86F. Free moisture plays a negative role and relative humidity plays a minor role in the asexual phase of powdery mildew in California. Ascospores are produced in the fall and winter.
Monitoring and Treatment. Powdery mildew can be monitored by visual inspection and by use of weather-driven disease risk models, particularly in the early season. Treatment is largely based on prevention. All preventive fungicides have a standard treatment interval, based largely on the residual activity of the material. Preventive treatments for powdery mildew are necessary as long as temperatures are conducive to growth and development. In the San Joaquin Valley this period occurs from shortly after budbreak through early July. There is increasing use of localized, weather data combined with disease risk models for scheduling of chemical applications (69). The Gubler-Thomas model is estimated to be used currently on approximately 80,000-100,000 acres to help determine when weather conditions indicate a higher risk of disease outbreak (35). When this risk is high, the interval between treatments is shortened, whereas if the risk is low, intervals can be lengthened. Risk is higher when temperatures fall between 70 and 86F, but below 95F. Wet springs can extend the release period of ascospores.
Ampelomyces quisqualis is a naturally occurring fungal hyperparasite of powdery mildew, which has recently been registered under FIFRA as a pesticide (AQ10), and is also listed below under chemical controls for powdery mildew. A. quisqualis has been found to provide some natural control on the east coast. Under California conditions AQ10 has been shown to give excellent diseases control when used early in the spring and applied prior to disease onset. It also has been shown to give excellent control of powdery mildew when used during periods of low disease pressure (37).
Powdery mildew materials can be classified as preventatives or contacts. The vast majority of materials used are preventatives. Late season control is dependent upon early season disease control and reduction in inoculum and subsequent infection. Sterol-inhibiting fungicides (SIs, also called demethylation inhibitors or DMIs), such as triadimefon, myclobutanil, and fenarimol, triflumizole(BAYLETON, RALLY, RUBIGAN and PROCURE, respectively), as well as sulfur or copper are not used as an eradicants, but as protectants before infection is present. Lime sulfur is sometimes used during the dormant season to kill ascospores, but on table grapes this is rare, as viable ascospores are not produced in the Southern San Joaquin Valley. DMIs are systemic, but only for 1 or 2 cm around each spray droplet. Therefore, thorough coverage is critical for efficacious disease control. Oil, soaps, potassium bicarbonate (KALIGREEN), cinnemaldehyde (VALERO), and wettable sulfur are contact materials that kill mildew spores on contact but cannot prevent tissue colonization after infection. A true eradicant for powdery mildew is oil used as a 2% spray (23), although use of oil on table grapes is not recommended after bloom because it can spot the berries. Treatments for powdery mildew on table grapes are continued until harvest to minimize the risk of stem infections.
BOTRYTIS BUNCH ROT
Damage. Botrytis is a fungal disease which can infect grape leaves, shoots and berries (49). Because its optimal temperature is 72F and it does not grow above 90F, and because its spores require free moisture for germination, it is a more serious problem in the coastal regions, especially if there is rainfall in the weeks prior to harvest. Once berries are infected with Botrytis, they may split and leak, allowing new spores to germinate on neighboring clusters. Spores from infected fruit can directly infect intact berries, but also enter through wounds caused by insect, bird or other mechanical damage, or damage caused by powdery mildew. Thin skinned (e.g., Ruby Seedless) varieties are particularly susceptible. The risk of berry infection increases with increasing berry sugar.
Description of Symptoms and Disease Cycle. Botrytis overwinter as dormant structures called sclerotia. With spring rains, sclerotia germinate and produce gray spores (conidia). Early season shoot, leaf and flower blight may occur following spring rains, and brown lesions may appear. "Latent infections" can occur when flowers become infected during bloom, and the fungus lays dormant within the berry until sugar concentration increases. The fungus then resumes growth and spreads throughout the berry, and the skin of infected berries will slip off easily. This can occur when the table grapes are in storage. Tighter clustered varieties and clones tend to have more bunch rot. An infected berry or cluster that sporulates takes on a characteristic fuzzy gray appearance.
Monitoring. Botrytis can be monitored by visual inspection for grey mold symptoms on leaves, shoots, flowers, and/or clusters. In the past, fungicide treatments were largely based on prevention and a calendar or plant growth based timing of fungicide applications. Recent work out of UC Davis in California and Chile has shown that weather conditions can be monitored to estimate the risk of infection and to time chemical treatments based on the temperature and wetness requirements of the fungus (4). Botrytis infection increases with longer periods of wetness from rain or dew, and temperatures within its wide developmental range of 1 to 30 C (35- 86 F) with a temperature optimum of around 18-22 C (65- 72 F).
There are two key treatment periods if wet weather conditions occur: 1) bloomtime and 2) pre-harvest. Preventive treatments are commonly applied at bloomtime, pre-close (late-June to mid-July, and veraison (early to late-July). Thorough coverage is essential for all fungicide treatments.
SUMMER BUNCH ROT (SOUR ROT)
Aspergillus niger, Alternaria tenuis, Botrytis cinerea,
Cladosporium herbarum, Rhizopus arrhizus, Penicillium spp., and others.
Damage. The summer bunch rot complex consists are secondary invaders that take advantage of mechanical damage to berries. Berries may split due to tight clusters or powdery mildew, or may be damaged by insects (especially OLR) or birds. Damaged berries are quickly colonized by fungi and bacteria, and once a single berry becomes infected, bunch rot can spread throughout an entire cluster. Dripping juice from a rotting cluster can spread infection to adjacent healthy clusters. Masses of spores develop on the surface of infected berries. Bunch rot often culminates in sour rot, especially in the southern San Joaquin Valley. Sour rot is caused by a variety of microorganisms, including Acetobacter bacteria, which are spread by vinegar flies attracted to the rotting clusters.
Description of Symptoms and Disease Cycle. As berries ripen and sugar content exceeds 8%, injured fruit become increasingly susceptible to invasion by a wide variety of naturally-occurring microorganisms. Invasion occurs at the point of injury caused by insect or bird feeding, mechanical or growth cracks, or lesions resulting from powdery mildew or black measles. The resulting rot can be severe as it progresses beyond the original injury. A characteristic vinegar smell is present if sour rot organisms are present.
Monitoring. Growers and PCAs should monitor for rotting clusters by visual inspections between veraison and harvest.
There are some promising biologicals for use as antagonists against the bunch rot complex. The bacterium Pseudomonas fluorescens (BlightBan®) has performed well in this manner (R.A. Duncan, personal communication), but is as yet not registered for use on grapes.
PHOMOPSIS CANE AND LEAFSPOT
Damage. Phomopsis is a fungal disease which is most severe when spring rainfall is high (35). It is common in northern grape growing regions where spring rains are common after bud break. Splashing rain is required for infection. Basal leaves with heavy infection become distorted and usually never develop to full size. Canes may be stunted or break off at the base, and infected buds may not open. Severe infections may cause clusters to shrivel and dry up. On cane pruned varieties, stunted canes may not allow enough fruiting wood for the following year's crop.
Description of Symptoms and Disease Cycle. Phomopsis overwinters as fruiting bodies called pycnidia. In spring, spores are exuded from the pycnidia, and infections can occur anytime that rain splashes spores onto green leaf tissue. Tiny dark to brown spots with yellowish margins occur on leaf blades and veins, appearing several weeks following rain. On shoots, black scabby streaks appear. Infected canes appear bleached during the dormant season. Severely affected cane or spurs exhibit an irregular dark brown to black discoloration intermixed with whitish bleached areas.
Monitoring. Growers and PCAs should look for bleached out canes to determine overwintering inoculum potential and to prune out infected canes or spurs.
No biological controls have been identified that are effective against phomopsis cane and leafspot.
In all areas, spring foliar treatments may be advisable if the risk of rain after budbreak is high, or if overhead water is used for frost protection. Apply materials before the first rain after bud-break and before 0.5 inch shoot length (and again when shoots are 5 to 6 inches in length).
MEASLES (BLACK MEASLES / SPANISH MEASLES)
Damage.For many years the cause of measles was unknown, but recent work points to several species of wood rotting fungi, particularly in the genus Phaeoacremonium. Affected leaves display necrotic interveinal areas with a chlorotic outline. Severely affected leaves may drop and canes may dieback from the tips. On berries, measles is expressed as small, round, dark spots, each bordered by a brown purple ring. These spots may appear at any time between fruit set and ripening. In severely affected vines the berries often crack and dry on the vine. This disease is more prevalent in areas with consistently high summer temperatures such as the San Joaquin Valley, although the disease in recent yrs has been observed in all production areas including the central coast. Generally, plantings that are 10 years of age or older are affected, although measles has been seen on fruit and foliage on 2-4 year-old vines.
Description of Symptoms and Disease Cycle. Symptoms may occur at any time during the growing season but are most prevalent during July and August. Most likely, spores of Phaeoacremonium spp. enter the vine through pruning wounds.
Cultural, Biological and Chemical:
Although there are no recommended treatments for measles at this time, because it is most likely a pruning wound infection, strategies to minimize pruning cuts (as for Eutypa and other canker diseases) should minimize the risk of measles infection.
EUTYPA AND OTHER CANKER DISEASES
Damage. Eutypa and other canker diseases are caused by two species of fungi, Eutypa lata and Botryodiplodia theobromae (34). Eutypa dieback is an important problem in the Northern San Joaquin Valley, but is also found in the Southern San Joaquin Valley. Bot canker is the main cause of arm and cordon death in the southern San Joaquin Valley region. Both Eutypa and Bot canker enter the vine through pruning wounds, and move slowly towards the roots. The fungi form cankers in the permanent wood of the vine, and eventually cause death of spurs, cordons, and ultimately, the entire vine.
Description of Symptoms and Disease Cycle. Eutypa survives in diseased wood and produces fruiting bodies (perithecia) in old, affected host tissue under conditions of high moisture. Eutypa spores are produced in the northern part of California in grapevines, apricots, cherries, kiwi, manzanita and Ceanothus. Ascospores are discharged from perithecia soon after rainfall. Bot canker produces fruiting bodies (pycnidia) on the surface of canker, which produce spores. Spores of both diseases are carried with winter storms, and infection on grapes occurs through pruning wounds. Symptoms in the wood of both diseases are similar in appearance, characterized by wedge-shaped, darkened cankers that develop in the vascular tissue. Eutypa dieback delays shoot emergence in the spring, and causes shoot stunting and a "witch's broom" appearance. Leaves are chlorotic and tattered. No foliar symptoms have been associated with Bot canker. Disease is not generally visible in vines younger than 5 to 6 years old and is seen most frequently in vineyards established for 10 or more years.
Monitoring. Eutypa and bot canker can be detected by observing dead sections of cordon. Growers and PCAs should monitor for Eutypa by looking for symptoms in late spring before stunted shoots can be masked by growth from adjacent shoots.
A few fungal antagonists to Eutypa have been identified and applied experimentally to pruning wounds to control it. Research in California has shown that Fusarium lateritium and Cladosporium herbarum can colonize pruning wounds and provide control of Eutypa (52), but no fungal antagonistic products are available commercially.
Chemical treatments are most effective if applied directly to the pruning wounds immediately after pruning.
Damage. The bacterium that causes Pierce's disease lives in the water-conducting system of plants (the xylem) and is spread from plant to plant by xylem-feeding sharpshooters (see Sharpshooters). Symptoms of Pierce's disease first appear as water stress in midsummer and are caused by blockage of the water-conducting system by the bacteria. Leaves become slightly yellow or red along margins in white and red varieties, respectively, and eventually leaf margins dry or die in concentric zones. By mid-season some or all fruit clusters on infected canes may wilt and dry. Tips of canes may die back, and roots may also die back. Vines may deteriorate rapidly after appearance of symptoms.
Description of Symptoms and Disease Cycle. Sharpshooters are active in the spring after average temperatures warm up above 59 F, and can transmit the bacterium to the vines anytime thereafter. Usually only one or two canes on a vine will show Pierce's disease symptoms in the same season that infection has occurred, and this happens late in the season. Symptoms gradually spread along the cane from the point of infection out towards the end and more slowly towards the base. In the following year, some canes or spurs may fail to bud out. New leaves become chlorotic (yellow) between leaf veins and scorching appears on older leaves. From late April through summer infected vines may grow at a normal rate, but the total new growth is less than that of healthy vines. Not all vines which have been infected will develop the disease. The probability of recovery depends on variety, the date of infection and the age of the vineyard. Once the vine has been infected for over a year (i.e., bacteria survive the first winter) recovery is much less likely. Young vines are more susceptible than mature vines, probably because during the training period, much less wood is pruned off than mature vines. Infections are often removed with pruning. Rootstock species and hybrids vary greatly in susceptibility. The date of infection strongly influences the likelihood of recovery. Late infections (after June) are least likely to persist the following growing season.
Monitoring. Growers and PCAs can monitor for insect vectors such as sharpshooters, and can make visual observations for symptoms of Pierce's disease.
No biological controls are known for Pierce's disease.
Damage. Downy mildew is a fungus which is common in areas with high summer rainfall (eastern USA and Europe) (58), but was unknown in California until 1995. It was problematic in several South San Joaquin Valley vineyards in the wet springs of 1995 and 1998. Oily lesions develop on the upper sides of the leaves, and the fungus sporulates in a dense white fluffy growth within the lesions. Severely infected berries and clusters may completely shrivel within weeks.
Description of Symptoms and Disease Cycle. The fungus overwinters as oospores in leaf litter and soil, as well as in buds and shoot tips on the vine. Spring rains splash the spores onto green tissue. Downy mildew attacks all green parts of the vine. Lesions can be yellowish and oily or angular and yellow to reddish brown, depending on leaf and lesion age. Infected shoot tips thicken, curl and become white with sporulation, eventually dying. Young berries are more susceptible to the disease than more mature berries.
Monitoring. Growers and PCAs should be on the lookout for signs of the disease, especially during wet springs. Eradicative treatments can be applied at the first sign of the disease.
No biological practices have been identified for this disease.
Materials for downy material can be classified as preventatives or contacts. No systemic materials are registered (some systemic fungicides against downy mildew are used in other countries).
Damage. Gall formation is the typical symptom of this disease. Crown Gall is an occasional problem in grapes.
Description of Symptoms. Galls may be produced on canes, trunks, roots, and cordons and may grow to several inches in diameter. Internally galls are soft and have the appearance of disorganized tissue. Galls commonly develop where plants have been suckered or injured during cultivation or pruning. Galls frequently will appear where the vine tissue has been damaged by a severe freeze. Natural growth, cracks and woody tissue also appear to be good sites for infection. The pathogen can be transmitted by any agent that contacts the contaminated material.
There are no biological controls that are effective against the grape crown gall strain, however, Agrobacterium radiobactor, a non-pathogenic competitor, does provide effective control of this pathogen on other crops (62).
In areas where winter injury to the vines occurs, chemical treatments may be effective.
Root Knot Nematodes, Meloidogyne incognita, M. javanica, M. arenaria, and M. hapla
Ring Nematode, Criconemella xenoplax
Dagger Nematodes, Xiphinema americanum and X. index
Root Lesion Nematode, Pratylenchus vulnus
Citrus Nematode, Tylenchulus semipenetrans
Plant parasitic nematodes are microscopic, unsegmented roundworms that feed on plant roots by puncturing and sucking the cell contents. They live in soil and within or on plant tissues. Of the many genera of plant parasitic nematodes detected in soils from California vineyards, root knot, ring, dagger, root lesion and citrus nematodes are the most important (50). Other nematodes associated with grape in California include stubby root nematode, Paratrichodorus minor; spiral nematode, Helicotylencus pseudorobustus; and needle nematode, Longidorus africanus. Of these, only needle and spiral nematodes have been found to be damaging to grapes in California. Pin nematode, Paratylenchus hamatus, is frequently found in vineyards but is not thought to cause damage.
Dagger, ring, and root lesion nematodes are most prevalent in north and central coast vineyards, and in the San Joaquin Valley. Root knot and citrus nematodes occur most commonly in the San Joaquin Valley and southern California. The needle nematode is found mainly in southern California. Presence of species, soil texture, grape cultivar, cropping history, weed spectrum, and growing region are the determining factors as to which nematode is present in which vineyard as well as the extent of damage they will cause.
Damage. Plant parasitic nematodes feed on roots, reducing water and nutrient uptake, and ultimately, vigor and yield of grapevines (50). Nematodes fall into two categories with respect to feeding: some feed externally on roots (ectoparasitic nematodes), and some penetrate into roots and feed internally (endoparasitic nematodes). Damage is often associated with soil textural differences. Root knot nematode (RKN) (Meloidogyne spp.) is most damaging on coarse-textured soils (sands, loamy sands and sandy loams). RKN penetrates into roots and induces giant cell formation, usually resulting in root galls. Giant cells and galls disrupt uptake of nutrients and water, and interfere with plant growth. Ring nematode (RN) (Criconemella xenoplax) can be damaging on coarse or fine-textured soils, but does not do well on fine sandy loam soils. RN feeds externally. The dagger nematode, X. index, can cause yield reduction in some varieties, but is more important for its transmission of grapevine fanleaf virus. A closely related species, X. americanum, is the most common species of dagger nematode, weakening the vine by feeding just behind the root tip and vectoring yellow vein virus (also known as tomato ringspot virus). Root lesion nematode restricts the growth of roots as it feeds and migrates in and out of roots; it can be especially damaging to newly planted vines. Citrus nematodes establish feeding sites with their heads embedded in cortical tissue and their posterior ends outside the roots.
Life History of the Pest. Juvenile RKN and other endoparasitic nematode species penetrate roots and establish feeding sites in the vascular tissues. Their development stimulates the vine to produce galls, which may be occupied by one or several adult female RKN. Upon maturity, the sedentary RKN female may lay up to 1,500 eggs apiece. RN and other ectoparasitic species remain in the soil during their entire life cycle.
Monitoring. To make management decisions, it is important that growers know the nematode species present and have an estimate of their population level. Growers and PCAs may take soil samples and have them assayed for nematodes. Soil and roots samples should be taken within the row, preferably one to two feet from the trunk, down to a depth of 3 feet (50). Samples may be taken any time of the year, but the economic threshold will vary.
There are many soil dwelling organisms that will feed on nematodes, including predatory species of nematodes. However, they usually do not provide enough mortality to control plant parasitic nematode populations. Predatory nematodes are considered to have low survivorship in agricultural fields. They reside in the shallower depths of the soil and do not penetrate roots.
Vineyards planted in fumigated ground are known to have improved growth and yields compared to those planted on non-fumigated ground.
Weed Management. Weeds reduce vine growth and yields by competing for water, nutrients, and sunlight, and typically are controlled to enhance the establishment of newly planted vines and to maintain growth and yield of established vines. Competition is most severe during the first 2 to 3 years of the vine's life or where root growth is limited. For mature vines, competition is greatest under drip irrigation with decreasing competition under furrow and basin flood irrigation. Annual weeds are more easily controlled than perennial weeds. Perennials typically are less susceptible to herbicides and to cultivation. Weeds have impacts other than competition and include interference with harvest because of a tall growth habit (e.g., prickly lettuce and horseweed), seed contaminant in the crop (e.g., sandbur in raisins and black nightshade in mechanically harvested grapes), and finally, interference with pesticide applications for insect and disease control. However, weeds can also provide some benefits if carefully managed. They can provide erosion control on steep hillsides. Weeds can keep the dust down, especially along roadsides, and can also improve soil structure by adding organic matter, providing root channels and exuding soil stabilizing gums, all of which can improve water infiltration. In areas with intense sunlight, weeds can cut down on reflected light from the vineyard floor, which can potentially sunburn grapes. However the long-term benefit of using weeds as a vineyard floor cover are unclear since these weeds are a continued source for weed colonization of the vine row.
Weed Management As Part of IPM. Weed management is part of an overall vineyard management system. Plants on the vineyard floor influence other vineyard pests such as insects, mites, nematodes, diseases and vertebrates. As an example, bermudagrass, dallisgrass, and many other grassy weeds have been identified as host reservoirs of the Pierce's disease bacterium. This pathogen can be vectored to grapevines by sharpshooter leafhoppers that have fed on host reservoirs. Many species of broadleaf weeds and perennial grasses are hosts to nematodes that also infest grapevines. Some weeds are alternative hosts for insects such as OLR and orange tortrix. Gophers are most prevalent in non-tilled vineyards and are common where broadleaf weeds predominate. They feed on vine roots and can kill young vines. Weeds provide a good habitat for field mice or voles, which can girdle and kill vines.
Monitoring. Weed surveys, at least once a year, allow growers to identify the spectrum of weed present within the vineyard and to develop a weed management strategy for control. These surveys are the basis for decisions about herbicide choice or cultivation equipment and practices. In season monitoring aids decision making for timing of postemergent herbicide applications. Proper postemergent herbicide timing allows application of the lowest dose while maintaining control.
Few vineyard weed biological controls have been identified, although there are biological control agents for puncturevine and yellow starthistle.
Herbicides registered for use in vineyards vary in their mode of action, soil persistence, and the timing and method of application. Pre emergent herbicides are applied directly on the soil surface before seed germination and growth of the weeds. Weeds are killed as they germinate. This type of treatment does not typically control established weeds or dormant weed seed. Herbicides applied to established, growing weeds are called post-emergent herbicides. Post emergent herbicides may kill tissue directly contacted (contact herbicides) or they may translocate within the plant (systemic herbicides).
Overview. A number of vertebrate species may move into or live near grape vineyards and seek the vineyards for food or shelter. The potential for damage by vertebrates varies from region to region. Migratory and resident birds can cause significant damage. Vineyards located near rangeland, wooded areas or other uncultivated areas are more likely to be invaded or re-invaded by certain vertebrates. Predators, diseases and food sources all may influence a vertebrate populations. Predators such as coyotes, foxes, snakes, hawks and owls feed on rodent and rabbit species. Growers cannot, however, rely on predators to prevent rodents or rabbits from becoming agricultural pests.
House Finch - Carpodacus mexicanus
Robin - Turdus migratorius
Starling - Sturnus vulgaris
Damage. Several species of birds can cause severe damage when they feed on ripening berries in vineyards. House finches are one of the most troublesome bird pest in grapes. They are residents in all grape growing regions and may feed on berries whenever ripe fruit is present. Robins are a common pest in grape vineyards feeding on ripening berries. Starlings may feed in vineyards any time ripening fruit are present.
Monitoring. The best strategy for reducing bird damage depends on the species feeding on the crop. Growers and PCAs should identify the birds that are causing damage before choosing controls. Keeping records of bird problems and the time of year they occur helps growers to plan control actions.
CALIFORNIA GROUND SQUIRREL
Damage. Ground squirrels are primarily a nuisance in vineyards, but can be a serious problem if populations build up to high levels. The squirrels gnaw on vine trunks, sometimes girdling and killing young vines. They may also feed on shoots and fruit sometimes damage polyethylene irrigation hoses.
Monitoring. Growers monitor for ground squirrels by checking the perimeter of the vineyard about once per month for animals or their burrows. If monitoring indicates that a squirrel population is moving in, they can be controlled with traps, fumigants, or toxic bait.
Description of Pest. Pocket gophers are important vertebrate pests. They gnaw on root systems and girdle vines below the soil line. Their burrows run through the vineyard, diverting water and contributing to soil erosion.
Monitoring. Growers monitor for gophers by inspecting vines near the borders of the vineyard where gophers may move in from adjacent fields. Gophers should be controlled as soon as they are detected.
Damage. Meadow voles, which are also referred to as meadow mice or field mice, inhabit roadsides, meadows, canal banks, fence-rows and many field crops. When mouse populations reach high levels in their native grassy habitats, they invade and occupy neighboring vineyards, gnawing on trunks and cordons.
Description. Full-grown meadow voles are larger than house mice but smaller than rats. They feed on grasses, so grassy areas are a good food source as well as habitat for them. Well-established populations can be recognized by the network of small runways through the grass or other cover and the openings of numerous shallow burrows. Meadow voles are active year round, day and night.
Monitoring. Growers monitor the vineyards by visually looking for active runways and burrows. Snap traps baited with a mixture of peanut butter and oats are also used to monitor vole populations.
Meadow voles are classified as non-game mammals and may be eliminated in any manner at any time if they are injuring crops.
Damage. Deer feed on vines and berries in vineyards located near good deer habitat. Deer are most likely to be a problem from late spring to midsummer in low-elevation vineyards. Deer feed at night and early in the morning.
Monitoring. Growers identify deer pests by footprints in the field and deer droppings.
Damage. Coyotes damage drip irrigation hoses.
Primarily Jackrabbits: Lepus californicus
Damage. Rabbits can cause problems in new vineyards. Rabbits feed on the leaves and stems of young plants. Jackrabbits are the primary pest though cottontail and brush rabbits also cause adverse affects.
California Grape Advisory Team
FQPA Grape Partnership
Statewide: Diseases and sustainable
Dr. Jenny Broome
UC Sustainable Agriculture Research and Education Program
University of California
Davis, CA 95616
Dr. Doug Gubler
Department of Plant Pathology
University of California
Davis, CA 95616
Dr. Frank Zalom
UC IPM Project
University of California
Davis, CA 95616
Dr. Kent M. Daane
Biological Control Specialist
Kearney Ag Center
University of California
9240 South Riverbend Ave.
Parlier, CA 93648
Dr. Mike McKenry
UC Cooperative Estension
Kearney Ag Center
University of California
9240 South River Bend
Dr. Clyde Ellmore
University of California
Dr. Tim Prather, IPM Advisor
Kearney Ag Center
University of California
9240 South Riverbend Ave.
Parlier, CA 93648
Southern San Joaquin Valley Region
Walt Bentley, IPM Advisor
University of California
Kearney Ag Center
Dr. Michael Costello
Costello Agricultural Research & Consulting
P.O. Box 165
Tollhouse, CA 93667
Ross A. Jones, Director Research
California Table Grape Commission
392 W. Fallbrook, Suite 101
Fresno, CA 93711-6150
23595 Road 140
Tulare, CA 93274
Dr. Mark Mayse, Entomology Professor
Department of Plant Science
California State University, Fresno
Fresno, CA 93740
P.O. Box 728
Shafter, CA 93263
Jack G. Zaninovich Farms
19745 Avenue 128
Porterville, CA 932257
California Pesticide Impact Assessment Program
University of California
PLANT GROWTH REGULATORS
Description. Gibberellic acid is applied on nearly all table grape acreage. It is applied at a median rate of 0.02 lb ai/ac, although the rates for bloomtime application are much lower than the rates at berry set. It is applied at bloomtime to thin the number of berries per cluster, and at berry set to enlarge the berries.
Description. Ethephon (ETHREL) is used on 8% of table and raisin grape acreage at a median application rate of 0.25 lb ai per acre. Ethephon increases color, sugar content and decreases the acidity of grapes. It has the negative effect of reducing berry firmness and reducing storage life. It can also reduce the vigor of vines.
Description. Hydrogen cyanamide (DORMEX) is used on about 3% of table grape acreage at an application rate of about 15 lb ai per acre. This plant growth regulator is used to increase budbreak in areas of low winter chill, particularly in the Coachella Valley. It is used on approximately 50% of the grape acreage in this region.
Description. Botrytis is the most common post harvest disease of table grapes. Disease in storage can come from several sources, either direct infection of berries and clusters just prior to harvest in the field, infections can occur in the post harvest handling phase, or "latent infections" can come from earlier flower infections and then the fungus lays dormant within the berry until sugar concentration increases. After the grapes are harvested and placed into cold storage, the fungus can continue to grow at cold temperatures and spread throughout the berry and between berries. The skin of infected berries will slip off easily, and production of conidia gives the fungus its characteristic fuzzy gray appearance.
Life History of the Pest. See Botrytis Bunch Rot in the Major Diseases section.
Monitoring. Monitoring for Botrytis in storage is done by taking berry samples at harvest and holding them at room temperature in a humid chamber. Infections can be detected within a week.
Storing table grapes at very cold temperatures (0-2°C or 32-35°F) will slow the development of the disease but can not kill the fungus and upon removal from cold storage the fungus will resume growth and sporulation.
No biological controls are used for control of Botrytis on table grapes in storage.
INSECTS AND SPIDERS
Description. Table grapes in storage can be infested by low levels of a variety of insect pests, most of which are described above. Whereas these insects pose little if any risk of damage to the stored grapes, they may require treatment for grapes destined for export. Some countries which import California table grapes have quarantines for specific insect pests.
There are no known cultural controls which will eliminate the possibility of insect and spider contamination of table grapes.
There are no known natural enemies which will help control table grape pests in storage.
Research results alone will not initiate changes in farming practices, and there is a critical need for information delivery methods to growers. Early efforts to implement integrated pest management (IPM) systems and the use of low impact chemicals in grapes include the California Clean Growers, which was established in 1988. The model system which has proven successful over the past six years is the Biologically Integrated Orchard Systems program (BIOS), now known as the Ag Partnership model.
The Ag Partnership model recognizes that agricultural systems are made up of many biological components, including the crop, but also the soil dwelling organisms (microbes, nematodes and arthropods), the organisms that exist on the crop, and even the weeds. The Ag Partnership model promotes farming practices that encourage the beneficial organisms in the system, and encourages the use of practices and inputs that have minimal negative impact on beneficials, human health and the environment. Relatively "high risk" materials such as organophosphate and carbamate insecticides, and B2 carcinogens, are strongly discouraged. Because soil and plant health are often important in limiting the impact of pests, practices such as long term soil building, optimizing plant nutrition levels and improving irrigation efficiency can increase plant tolerance to pest attack and may also prevent pests from reaching the economic injury level. At the crux of the model is the active participation of growers, who are directly involved in defining problems, developing creative approaches to their solutions, participating in research efforts, and helping deliver educational information to fellow program participants and wider audiences. Grower input is integrated with that of cooperative extension advisors, researchers, PCAs and community members.
Successful grape programs utilizing the Ag Partnership model include the Lodi-Woodbridge BIFS (55), Central Valley Biologically Integrated Vineyard Systems (11), the Central Coast Vineyard Team (9), the Sonoma Valley Vintners and Growers (70) and the Napa Sustainable Winegrowing Group (54). Although funding groups such as the California Table Grape Commission and various programs within the University of California have done a good job of funding grape IPM research projects, much more can be done on the part of these groups to support Ag Partnership projects, expand grower participation, and develop similar groups for table grape growers.
This section addresses pest research priorities for California table grapes. Needs are prioritized in three ways: By the percentage of grape acreage in California treated with FQPA Priority I materials, by the number of registered, effective chemical substitutes for FQPA Priority I materials, and by a survey of California table grape growers conducted by the California Table Grape Commission (CTGC) in 1999 (Table 1). Research needs can be separated into three areas: 1) the development and evaluation of alternative chemical control methods and 2) short term research needs including cultural and biological controls, and basic pest and plant biology and 3) long term research needs, including host plant resistance, interactions within the agroecosystem, and foreign exploration for natural enemies.
Column 1 of Table 1 prioritizes table grape pest research needs based on the percentage of raisin and table grape acreage in California treated with FQPA Priority I materials in 1997. Weeds spider mites, and powdery mildew are the top three priorities, with at least 35%, 34.5%, 34% of raisin and table grape acreage treated, respectively. These are followed by Botrytis, nematodes, leafhoppers and omnivorous leafroller with at least 10.5%, 10%, 7% and 7% of raisin and table grape acreage treated, respectively. Mealybugs and sharpshooters received treatment on at least 6% and 3% of raisin and table grape acreage, respectively.
Column 2 of Table 1 is based on the number of registered, effective chemical substitutes for FQPA Priority I materials on table grapes. The top three priorities for table grapes are mealybugs and root knot nematode, because there are currently no effective Priority II and III materials registered against them which can substitute for FQPA Priority I materials. For mealybugs, only one in-season chemical is registered (Admire®), but it is a drip-applied systemic which cannot be considered a substitute for foliar OPs or carbamates. There are no Priority II or III substitutes for fenamiphos (Nemacur®), a Priority I material used to treat root knot nematode, an endoparasitic nematode. Ectoparasitic nematodes (e.g., ring nematode) can be effectively controlled with sodium tetrathiocarbonate (Enzone®), a Priority III material. The only Priority II or III materials registered against spider mites are either most effective under fairly narrow environmental conditions or are contact materials, which are not always consistently effective. Weeds have a significant contact herbicide available (glyphosate, Priority III), one Priority II contact material available, two Priority II pre-emergent herbicides available, and no Priority III pre-emergents. Spider mites, leafhoppers, omnivorous leafroller and sharpshooters each have one effective substitute, Botrytis has three and powdery mildew has four.
Column 3 of Table 1 comes from the CTGC, and is based on the responses of 135 table grape growers. The survey was not conducted in light of the FQPA, but rather includes all viticultural issues including variety evaluation, cultural practices, vineyard establishment and nutrition, as well as pest management issues. Listed are the top nine pest priorities of the survey. Such surveys are necessarily fluid; many of the priorities are long term, but some needs are reflective of the situation in the most current season (i.e., a survey taken after a bad mildew year will skew priorities toward mildew control).
Table 1. Order of table grape research priorities based on the percentage of table and raisin grape acreage treated with FQPA Priority I materials, the number of effective, registered substitutes for FQPA Priority I materials, and the1999 CTGC survey.
|Priority based on percentage of table and raisin grape acreage treated with Priority I materials (in parentheses )||Priority based on the number of effective, registered substitutes for FQPA I materials (in parentheses)||Priority based on 1999 CTGC survey|
|Weeds (35)||Mealybugs (0)||Mealybugs|
|Spider mites (34.5)||Root knot nematode (0)||Bunch rot|
|Powdery mildew (34)||Spider mites (1)||Powdery mildew|
|Botrytis bunch rot (10.5)||Leafhoppers (1)||Phomopsis|
|Nematodes (10)||OLR (1)||Nematodes|
Grape and variegated (7)
|Omnivorous leafroller (7)||Botrytis bunch rot (3)||Measles|
Grape and obscure (6)
|Weeds (4)||Spider mites|
Blue-green, green and red-headed (3)
|Powdery mildew (4)||Leafhoppers|
Current and alternative chemicals:
Table 2 lists the priority pest categories with corresponding FPQA Priority I, II and III materials. Based on the 1997 percentage of acres treated for these pests, the ranking is: spider mites, weeds, powdery mildew, Botrytis bunch rot, nematodes, leafhoppers, omnivorous leafroller, mealybugs and sharpshooters. Materials registered since 1997 are marked with an asterisk. Table 2 also lists unregistered alternative chemicals for these pests. Although all of the nine pest categories has at least one FPQA Priority I material registered for it, none is completely dependent on these materials, and in the short term, six out of the nine pests can be effectively controlled using currently registered Priority II and III materials as substitutes. The two exceptions are mealybugs and root knot nematode. In the long run, there are several alternative materials pending registration for powdery mildew and spider mites, and at least one for weeds, leafhoppers, sharpshooters, OLR, Botrytis and root knot nematode, but none for mealybugs.
Spider mites: Current and alternative chemical controls. The most widely used materials for spider mites, propargite (Omite®) and dicofol (Kelthane®), are FQPA Priority I. There is no direct substitute for either. The closest is fenbutatin-oxide (Vendex®), an FQPA Priority II material, which is not as effective in cool conditions (<80F), nor when spider mite population density is high. Narrow range oil is a contact material, and effective if coverage is thorough. However, its use is virtually restricted to pre-bloom because it removes the waxy bloom of the berries. Oil does not kill eggs and therefore several applications per season may be necessary. Cinnemaldehyde (Valero®), which was only registered in July 1999, is also a contact, and apparently has good kill on mite eggs (B. Murphy, personal communication). There are also several alternative materials pending registration, including avermectin (Agri-Mek®), pyridaben (Pyramite®), and clofentizine (Apollo®), all of which have been shown to be effective on Pacific mite (M.J. Costello, unpublished data).
Spider mites: Short term research needs. Specific guidelines are needed for the management of soil, water and dust, to keep spider mites under control. Research is needed to determine acceptable stress thresholds, e.g., vine water or soil chemistry status. There is also an increasing amount of data that shows that sulfur use exacerbates mite outbreaks. Research is needed on the mechanisms involved, and how sulfur can be integrated with other fungicides to minimize spider mite damage. There is also a great need for basic information on economic injury levels for Pacific mite and Willamette mite. The current guidelines are based on binomial sampling methods for Pacific mite, and are very inaccurate. There are no treatment recommendations for Willamette mite. New monitoring techniques are needed that provide more information on the total spider mite load on the vine, but which are economically justifiable. Information is needed on the release of the western predatory mite and other predatory mite species, including when to begin releases, how often to release, and the rate of release. The use of other spider mite predators such as the 6-spotted thrips also needs to be looked at.
Spider mites: Long term research needs. Because spider mite outbreaks are so obviously linked to soil conditions, long term research might look at the possibility of intense soil management (use of compost, gypsum, pH adjustment, other soil amendments) so that "problem" soils are no longer mite susceptible This would be a multidisciplinary effort, analyzing soil and vine condition as well as economics.
Weeds: Current and alternative chemical controls: Although there are no FQPA Priority III substitutes for any of the Priority I pre-emergent herbicides, diuron (Karmex®) is a Priority II material which is the closest substitute for the pre-emergents simazine and oxyfluorfen (Goal ®). Diuron is more effective than either of these materials in controlling annual grasses (46). However, diuron has been detected in groundwater (6), and is restricted in some areas (called pesticide management zones or PMZs). Another possible substitute is norflurazon (Solicam®), also a Priority II material, which controls a smaller spectrum of annual broadleaves, but is more effective at controlling annual grasses and certain perennial weeds (46). The most popular herbicide used on grapes in California is glyphosate (Roundup®, Touchdown®, Glyphos®), a contact herbicide which is a Priority III material. More use can be made of glyphosate, especially if it is used with new application technologies such as light activated sprayers and shielded misters, which will help apply contact materials more efficiently (T. Prather, unpublished data).
Weeds: Short term research needs: Successful weed control can be accomplished with in-row cultivation, and there are currently many in-row cultivators available, some of which allow for quicker, more efficient tillage than the traditional French plow. Another non-chemical technique is flaming. Research is needed on the most efficient, effective and economical use of these implements.
Other cultural weed controls have been looked into over the past decade. The best known was the "mow and throw" system, which chopped up cover crop and weed biomass from the middles and blew into the rows to create a weed smothering mulch (67). Other mulches, such as wood chips and almond hulls, could be used but have not had much attention. Synthetic mulches are expensive, but if amortized over the life of the mulch (ca. 10 years) are probably cost effective. Any of these mulches combined with a light activated contact herbicide sprayer would cut herbicide use drastically.
Cover crops could be considered a cultural weed control, but currently cover crops provide a very minor role in weed management. This is because the most difficult area for weed control (and where the vast majority of herbicides are applied) is within the row, but cover crops are grown in the middles, usually as winter annuals, and are usually disked up at budbreak or shortly thereafter. After this, they are replaced by a complex of summer weeds. Therefore, because cover crops are not grown in the most critical place (i.e., within the vine row) for weed control, and are usually not perennial, they currently have a very limited role to play in weed management.
There is potential for cover crops to serve as a component of weed management. Conventional perennial cover crops such as perennial ryegrass, creeping red fescue, orchardgrass, strawberry cover and white clover, can effectively crowd out weeds. However, they are high water users and can excessively de-vigorate vines. Also, because they require summer water, they are not compatible with drip irrigation systems. Perennial native grasses, which go dormant to varying degrees depending on the species, have great potential to be permanent, weed smothering and less competitive than resident weeds. Because of the great number of native grass species, there is a need for research on how to use them under different vineyard conditions. There is also potential for planting native grasses within the row, where weed control innovations are most needed. Such in-row cover cropping for weed control has been tested by innovative vineyard managers with Mondavi in the Napa Valley and Gallo of Sonoma, but has not been tested in table grape vineyards.
Subsurface drip irrigation can be looked upon as a cultural weed control for summer weeds. With subsurface systems, the drip line is buried 12-18" under the ground, usually 1-2 ft from the vine row. Irrigating underground cuts down on the number of weeds germinating at the soil surface. The downfall is the potential for vine root intrusion into the underground emitters, but this problem seems to have been solved with herbicide impregnated emitters. Also, in all but the lightest of soils, some water will make its way to the surface, so some weed growth can be expected. Some growers have begun to bury the subsurface drip line between the vine rows, where weeds can be disced up more easily. This system has no effect on winter weeds, and control for them would still be necessary.
Weed surveys can define which weed species are most problematic. At present, this can help growers decide which herbicide(s) would be most effective, but does little to reduce herbicide use. Weed surveys could help growers time contact herbicides more effectively, but little information exists on the most effective timing for different weed species.
Powdery mildew: Current and alternative chemical controls: The loss of myclobutanil (Rally®), triflumizole (Procure®) and triademefon (Bayleton®) would not have a major impact on powdery mildew management in the short run. Fenarimol (Rubigan®), a Priority III material, is a suitable substitute that is widely used. The loss would also not significantly affect powdery mildew resistance management, because fenarimol, myclobutanil and triflumizole all have a similar mode of action and currently cannot be used alternately for resistance management. Bayleton® has not been widely used for several years because of resistance. Azoxystrobin (Abound®) is a relatively newly registered material which is an effective preventative and eradicant, and falls into a novel chemical class, the strobilurines. The fungal parasite, Ampelomyces quisqualis (AQ10®), is an effective material in the cooler, more humid part of the season, and when powdery mildew infestation has not taken place and pressure is low. Several other materials, some of which are foliar nutrients, and others which fall into unique chemical classes, are pending registration and have potential to fit into a powdery mildew control and resistance management program (37). Finally, by far the most popular material for powdery mildew control is sulfur, which is a Priority III material. Many growers, both conventional and organic, rely exclusively on sulfur for powdery mildew control.
Powdery mildew: Short term research needs. Cultural practices such as canopy management may provide some powdery mildew control by influencing the ambient temperature. However, the incremental effect in most cases is so small that it probably would not allow for a reduction in treatments for powdery mildew. Note also that in warm climate regions such as the San Joaquin Valley, canopy management practices such as overhead trellising may actually make summertime temperatures cooler, thus improving conditions for mildew.
Cover cropping could be considered a part of powdery mildew management in wet springs, because it allows greater access to the vineyards (to apply treatments) under wet soil conditions.
Short term research needs also include evaluation of newly registered and soon to be registered products, and their role in resistance management. There is also a great need for information on how to use contact materials like Kaligreen®, Valero®, Elexa®, and foliar applied nutrients such as calcium (e.g., Vigor-Cal®), as well as how to use them with low volume sprayers. The Gubler-Thomas model needs to be more thoroughly evaluated and refined for different regions and vineyard conditions.
Powdery mildew: Long term research needs. Long term research of powdery mildew might involve the bioengineering of resistant genes, but this has proven difficult to do.
Botrytis: Current and alternative chemical controls: Four out of the five most commonly used materials for Botrytis are Priority I: Iprodione (Rovral®), mancozeb (Dithane®), benomyl (Benlate®), and captan. The fifth, dicloran (Botran®) is Priority II. There are also two newly registered materials: cyprodinil (Vanguard®) was found to be effective in a recent trial (R.A. Duncan, personal communication), and fenhexamid (Elevate®). Several other alternative materials have pending registration, including Elexa® and two biologicals (Serenade® and Trichodex®).
Botrytis: Short term research needs. Cultural controls such as leaf pulling and shoot positioning help increase air circulation and lower humidity. Most table grape growers already leaf pull and many utilize overhead or Y trellis systems to spread the canopy. Other cultural controls for Botrytis are crop load and irrigation management to help keep cluster and berry size low so as to reduce the risk of berry splitting. Work is needed on integrating leaf pulling, crop load management and irrigation management for Botrytis management with improvements in table grape quality and the management of leafhoppers. There is a need for research in evaluating the Broome model in different regions and under different vineyard conditions, and a need to test newly registered materials such as Vanguard®, Elevate® and soon to be registered materials such as Elexa® and the biologicals Serenade® and Trichodex®.
Botrytis: Long term research needs. Long term research might involve the mechanization of leaf removal, and bioengineering genes for resistance to Botrytis.
Nematodes: Current and alternative chemical controls. Two of the top three chemicals for nematodes are FQPA Priority I: Fenamiphos (Nemacur®) and carbofuran (Furadan®). The third chemical, sodium tetrathiocarbonate (Enzone®) is an FQPA Priority III material. Enzone® is a suitable substitute for Furadan®, as both are used primarily for the ectoparasitic nematodes such as ring nematode, and Enzone® has been found to be quite effective (M. McKenry, personal communication). However, there is no substitute for Nemacur®, which is primarily used for endoparasitic nematodes such as root knot nematode. Oxycom® and DiTera® are newly registered and have not been thoroughly tested on grapes in California, and there is much uncertainty on how to use them most effectively. There is therefore a need for more research on Oxycom® and DiTera®, and other new materials which are effective and environmentally safe. One possibility is Admire®, which appears to have an effect on root knot nematode similar to Nemacur®.
Nematodes: Short term research needs. Nematodes take advantage of stressed vines, so any measures taken which can minimize vine stress can reduce the risk of nematode damage. Soil management practices include preventing soil compaction and stratification, improve soil structure through the addition of compost, manure, cover crops, gypsum and other soil amendments, and proper fertilizer rates and timing. Still, there is little information available on specific indicators of good soil and water management which will help increase vine tolerance to nematode attack. Research is needed as to how irrigation practices for improving table quality will affect vine tolerance to nematode infestation. Short term research needs test newly registered materials such as DiTera® and Oxycom®.
Nematodes: Long term research needs. Information is always needed on rootstock resistance to nematodes, and the long term use of soil amendments such as cover crops and compost to help boost vine tolerance to nematodes.
Leafhoppers: Current and alternative chemical controls. There are five chemicals registered for leafhoppers which fall into Priority I of FQPA: Methomyl (Lannate®), carbaryl (Sevin®), dimethoate (Clean Crop®), naled (Dibrom®) and endosulfan (Thiodan®). All of these were commonly used for leafhopper control prior to 1995. However, in 1995 imidacloprid (Provado®), a Priority III material, was registered on grapes, and chemical control for leafhoppers has become largely dependent on this material. Although there have been attempts to associate the use of Provado® with secondary pest outbreaks, formal studies have not borne this out (22,43). It is an extremely flexible material for growers to use, because it is equally effective on leafhopper adults as well as nymphs, and because it can be used up to the date of harvest. The other Priority III materials registered for leafhoppers at present are not as effective, either because they are contact materials for which timing and coverage are critical (e.g., narrow range oil and soap), or are natural materials that have short residuals and are expensive (e.g., neem and pyrethrins/rotenone). Although the potential for resistance to imidacloprid is low and has not yet been reported in California, it is generally accepted that resistance to any insecticide will develop given enough time and exposure. That imidacloprid is being used almost exclusively at this time for leafhopper control is likely to increase the rate of resistance. It is therefore important that new materials be registered and incorporated into the arsenal of chemical tools for leafhopper control. An example is the insect growth regulator buprofezin (Applaud®), which has been effective in early trials (M.J. Costello, unpublished data). A very promising product is a material made of fine clay particles (kaolin [Surround®]). Another material pending registration is pyridaben (Pyramite®), which is effective on spider mites as well as leafhoppers.
Leafhoppers: Short term research needs. It is well known that leafhoppers are sensitive to irrigation management, and more research is needed on how leafhoppers respond to vine water status at different points in the season. Leaf pulling (leafing) at berry set is often a useful way to decrease first brood nymphal density. Irrigation management and leafing could be integrated with cover cropping and crop load management for leafhopper control, Botrytis management and improvements in table grape quality. Sticky tape has also been used successfully in trapping overwintering adults and reducing first brood nymphal density. Basic information is needed on economic injury levels and action thresholds for different varieties and in different regions. Improvements are needed in monitoring techniques and tools, e.g., the use of scanners to record nymphal counts in the field. Quick, effective, PCA-friendly field assessments of first brood parasitism by Anagrus are also needed. There is a need to register and test new chemistry materials for leafhoppers such as kaolin and IGRs.
Leafhoppers: Long term research needs. Mechanization of leafing will help reduce early season leafhopper numbers. Another important long term need is the importation of a more effective Anagrus species for variegated leafhopper.
OLR: Current and alternative chemical controls. For OLR, loss of the OPs and carbamates (all Priority I) will have a very minor impact on early season control, which currently is largely undertaken with cryolite (Priority III). Although there are no restrictions on the use of cryolite after bloom for table grape growers, there is a reluctance to use it late in the season because of concerns about leaf burn and/or berry damage. Bt can be used late, but is often not effective. Solutions to this problem include more research on how to make Bt more effective, including the development of forms that biodegrade more slowly. New materials such as spinosad (Success®) and tebufenozide (Confirm®) should be thoroughly tested and registered if found effective.
OLR: Short term research needs. Cultural practices can do a lot to keep OLR under control early in the season. Sanitation (removal/destruction of mummified clusters) and weed control can keep within-vineyard OLR density low, which minimizes early season infestation. Work is needed on showing the benefits of such cultural controls to growers. Two brands of OLR pheromone products have been registered (No-mate® and Checkmate®), but results have been erratic. The Achilles heel of mating disruption is the omnivorous diet of OLR and the OLR migration into the vineyard. More work is needed on mated female OLR flight patterns. Research is also needed on refining the OLR development model to time treatments. Better tools and methodology are needed to expedite monitoring. Development of a lure for OLR females might help PCAs determine the need for treatment. There is a great need for low risk chemicals that can be utilized late-season. Biological control research might involve the inundative release of Trichogramma, as has been done for coddling moth, and the use of flowering cover crops to enhance populations of other OLR parasites (braconid and ichneumonid wasps, tachinid flies).
OLR: Long term research needs. A long term research goal for OLR should be the importation of more effective natural enemies.
Mealybugs: Current and alternative chemical controls. The only two effective in-season foliar controls for mealybugs, methyl parathion and azinphos methyl, were restricted on August 1. Imidacloprid (Provado®), although registered, has not been found to be very effective. Imidacloprid applied through the drip system (Admire®) is the only other in-season control. Chlorpyrifos (Lorsban®) is a Priority I material which is registered for application as a delayed dormant (just prior to budbreak). It is effective, but with few other effective in-season controls available, it is possible that the use of Lorsban® might increase by growers as insurance sprays. There is a need for research into other early season controls, particularly the use of narrow range oil. There is also a need for new materials more specific to mealybugs which could be used late in the season.
Mealybugs: Short term research needs. Work is needed immediately on the vine mealybug, a new arrival in the San Joaquin Valley and a potentially devastating pest. Much effort has gone into foreign exploration for vine mealybug parasites, but effort also needs to be focused on domestic parasites, which have already attacked vine mealybug in Fresno County. For vine and other mealybugs, formal study is needed on trellising systems and pruning methods that can help minimize the risk of mealybug infestation. There is also a big need for mealybug monitoring tools that are quick and effective. There is also a need for more information on the various mortality factors that can act upon mealybugs during the season. Short term needs also include registration and testing of new chemistry materials, especially those which are somewhat specific to mealybugs. There are currently no effective in-season foliar chemical controls, and the efficacy of Admire® is still under investigation. Controlling ants may help contain the spread of mealybugs, but ant control alone will not necessarily provide mealybug control. More information is needed on low-risk ant baits such as Clinch® (active ingredient abamectin).
Mealybugs: Long term research needs. Effective biological controls are needed for the vine mealybug. Information is needed on why grape mealybug parasites are more effective in some vineyards than others. At present, no link has been established between parasitism levels and the use of chemicals. Research is also needed into vine tolerance factors: Are some vines more resistant to mealybugs?
Sharpshooters: Current and alternative chemical controls. Dimethoate (Priority I) has traditionally been the material used to treat border vegetation as well as vines for sharpshooters. However, imidacloprid (Provado®), it just as effective and is already widely used. However, just as with Erythroneura leafhoppers, there is a great concern about resistance, and there is a need for additional materials which are effective and environmentally safe. The particle film kaolin, because of its anti-feedant properties, would be particularly suitable against sharpshooters.
Sharpshooters: Short term research needs. Work needs to begin immediately on long term control strategies for the glassy winged sharpshooter. This strong flying insect feeds on a variety of cultivated plants, and is a carrier of Pierce's disease. The presence of this glassy winged sharpshooter may make moot efforts to control blue-green, green and red-headed sharpshooters. Research is needed on glassy winged sharpshooter biology, host preferences, non-host plants, migration patterns, overwintering abilities and biological controls. For the other sharpshooters, research is needed on better monitoring tools. Sharpshooters are not attracted to yellow sticky cards, and light traps are a possibility. There is a need to register and test new chemistry materials, like the particle film kaolin (Surround®). Research could also be conducted on the inundative release of natural enemies such as Trichogramma in the riparian areas.
Sharpshooters: Long term research needs. Long term research should focus on vine resistance to PD, including the incorporation of resistant genes into vines. Long term research needs for blue-green sharpshooters include riparian vegetation management, and the use of non-host barriers between the riparian corridor and the vineyard, such as cedars and conifers.
Minor pests. Minor pests are by definition not consistent in their pest status, which means that growers often are either unaware of their potential damage, or unwilling to take preventive measures because they may not be cost effective in any given year. Therefore, when minor pests reach the economic injury level, their control is largely taken care of with chemicals. There are almost no specific chemicals for minor pests, so broad spectrums (OPs and carbamates) are heavily relied upon. This is an extremely tricky area in terms of chemical alternatives. Few chemical companies have an economic incentive to develop products for minor pests. Research is needed into why outbreaks of minor pests like grapeleaf folder and grape bud beetle occur. However, there is little incentive to commit funding to this research because such little acreage is affected in any given year.
Table 2. Table grape pests, associated registered chemicals by FQPA priority status and alternative chemicals pending registration. Percentage of raisin and table grape acreage treated with a given material in 1997 is in brackets.
|Table Grape Pest||FQPA Priority I Chemicals||FQPA Priority II and III Chemicals||Alternative Chemicals|
•Paraquat dichloride (Gramoxone®)
•2, 4-D (Envy®)
|Spider mites: Willamette and Pacific||•Propargite (Omite®)
•Narrow range oil (various trade names)
|Table Grape Pest||FQPA Priority I Chemicals||FQPA Priority II & III Chemicals||Alternative Chemicals
|Powdery mildew||•Myclobutanil (Rally®)
|•Sulfur (various trade
•Copper hydroxide (various trade names) [36%]
•Narrow range oil (various trade names)
•Insecticidal soap (M-pede®)
•Azoxystrobin (Abound®) [2%]
•Ampelomyces quisqualis (AQ10®)*
•Potassium bicarbonate (Kaligreen®)*
|Botrytis bunch rot||•Iprodione (Rovral®)
|•Narrow range oil
(various trade names)
•Trichoderma sp. (Trichodex®)
|Table Grape Pest||FQPA Priority I Chemicals||FQPA Priority II & III Chemicals||Alternative Chemicals
•Metam sodium# (Vapam®)
•Myrothecium verrucaria (DiTera®)*
Grape and variegated
•Dimethoate (Clean Crop®)
•Narrow range oil (various trade names)
•Insecticidal soap (M-pede®) [3%]
•Azadirachtin (Neemix®) [0.05%]
|Omnivorous leafroller||•Methomyl (Lannate®)
•Bt (Various trade names)
Grape and vine
|Table Grape Pest||FQPA Priority I Chemicals||FQPA Priority II & III Chemicals||Alternative Chemicals
Green, red-headed and glassy-winged
*Material not registered on grapes in 1997.
Table 3. Key table grape pests, their current cultural, biological and other IPM controls, and short and long term research priorities.
|Table Grape Pest||Cultural, Biological and IPM Controls||Short Term Research Priorities||Long Term Research Needs|
Mulches: Synthetic and organic
Subsurface drip irrigation
|Test low volume
Test in-row cultivation implements
Test organic and synthetic mulches
Test in-row cover crop use
Develop action thresholds using contact herbicides
Implement weed surveys by growers/PCAs
|Spider mites||Soil, irrigation and dust
Reduce sulfur use
Monitoring and use of action thresholds
Release of predatory mites
|Use of sulfur
Timing/rate of predatory mite release
New tools/methodology to expedite monitoring
Use of 6-spotted thrips
|"Fixing" problem soils|
|Powdery mildew||Use of mildew model||Test new chemistry
Test, improve and implement use of mildew model
Improve dormant controls
Foliar nutrients to improve vine resistance
|Botrytis bunch rot||Leafing/canopy
Use of botrytis model
Regulation of crop load
|Test new chemistry
and biological fungicides
Test trellising systems
Biotechnology employing resistant genes
Soil amendments (cover crops, compost)
|Test new chemistry and biological materials||Improving soil health
Test new rootstocks
|Table Grape Pest||Cultural, Biological and IPM Controls||Short Term Research Priorities||Long Term Research Needs|
Vine water status
Establish EILs/action thresholds for varieties/regions
Register and test new chemistry materials
Irrigation/cover cropping to manage vine water status
|Importation of a more effective Anagrus for variegated leafhopper|
Use of OLR model
Use of natural enemies such as Trichogramma
Test pheromone disruption
|Importation of new natural enemies|
|Register and test new
Evaluate use of Admire
Use of ant baits
|Improve biological controls|
|Register and test new
Test light traps for monitoring
Inundative biological controls
|Biology and control of
Riparian vegetation management
Biotechnology employing resistant genes
Database and web development by the NSF Center for Integrated Pest Managment located at North Carolina State University. All materials may be used freely with credit to the USDA.