Prepared January, 2000
Production Regions
Vineyards are widely distributed across Virginia, with the bulk of the acreage found in the northern and central piedmont areas. These areas make excellent natural grape producing regions as a result of demographics as well as viticultural compatibility (4). The five viticultural areas approved by the federal government are as follows: Monticello, Northern Neck, North Fork of Roanoke, Rocky Knob, and Shenandoah Valley (4).
Virginia is suited for viticulture in being far enough south to avoid the extremely cold temperatures devastating to many vines in the North, while avoiding the more severe outbreaks of Pierce’s disease, common to areas in the deeper south. It should be mentioned, though, that winter cold injury is still the number one climatic constraint in the state. Virginia vineyards are roughly between 37° and 39° latitude, which is the same as for the North Coast region of California. Therefore the grapes can ripen fully in the temperate climate while retaining acidity. Site selection, however, is still an important aspect of grape production given that it affects both the frequency and severity of climatic problems and biological pests. Well-drained soils with a pH of 5.5-7.0 are required along with areas protected from frosts, which receive full sun.
The four categories of grapes grown in Virginia include Vitis vinifera, interspecific hybrids, native American varieties, and muscadine grapes (Muscadinia rotundifolia). The first group, V. vinifera accounts for over 80% of Virginia’s grape acreage. Chardonnay, Riesling, and Cabernet Sauvignon are among the most abundant varieties. The French hybrids such as Seyval and Vidal Blanc constitute 15% of grape acreage in the state, with native American varieties making up an additional 5%. Concord and Norton dominate the last group. Muscadine grapes represent a minor component of Virginia production given their generally inferior wine quality. Typically, bunch grape varieties are far more susceptible to fungal diseases and require a much more rigorous spray schedule.
Vinifera grapes are typically grafted onto a pest resistant rootstock, to provide protection and also to impart greater vigor to the above ground (scion) variety. The most commonly used rootstock in the mid-Atlantic region is Couderc-3309. Mgt 101-14 and C-1616E are also recommended for use within Virginia, though, they are usually more difficult to obtain from nurseries. All of the commonly grown bunch grapes can be planted in large, contiguous blocks without the need for cross-pollination, however some muscadine varieties do require a pollinator. All varieties are trained on trellis systems and annually pruned in winter to maintain production and vigor. Prior to the establishment of a trellis system, prepared soils are planted with a cover crop, such as fescue. Vines are then planted in weed free rows between the established sod middles. Cultivation is avoided given the erosion potential of most vineyard sites; however, herbicides are used to keep weeds from beneath the trellis. The majority of the state’s grapes are harvested by hand.
Insect descriptions were modified from Major Insect and Mite Pests of Grape in Virginia (5).
Chemical control recommendations were taken from the 1999 Horticulture & Forest Crops Pest Management Guide (6).
The most frequent insect pests reported for 1990 and 1991 were Japanese beetle, grape berry moth, and yellowjackets and other wasps, while the most severe mite problem reported was the European red mite. Less common insect pests were the ambrosia beetle, climbing cutworms, drosophila flies, grape cane girdler, grape curculio, grape erineum mite, grape flea beetle, grape leafroller, grape leafhopper, aerial phylloxera, grape plume moth, grape root borer, grape rootworm, grape skeletonizer, grapevine aphid, hornworms, June beetles, redbanded leafroller, and the rose chafer.
Japanese Beetle, Popillia japonica (Newman)
Japanese beetles (JB) along with other scarab beetles (i.e. rose chafer, Green June beetle, etc.) cause direct fruit injury as well as the characteristic skeletonization of leaves due to feeding, making them one of the most devastating insect pests to grapes in Virginia. JB emerge in June and July, preferring to feed on young leaves especially those that are exposed to full sunlight. Foliage feeding greatly reduces the ability of plants to photosynthesize and hence decreases productivity through the almost complete annihilation of leaf tissue.
Chemical Control: Usually provides the only truly effective form of control (see recommendations below). Acceptance, on the part of the growers, of some defoliation on mature vines may reduce the number of chemical applications necessary for JB control. Slight defoliation has not been shown to have significant effects on grape yield.
Cultural Control: Clean harvesting, which prevents an accumulation of overripe fruit, helps to prevent beetles from being attracted to plantings. Plowing or cultivation can destroy pupae in the soil.
Grape Berry Moth, Endopiza viteana (Clemens)
The grape berry moth (GBM) has been considered one of the most severe grape pests in Virginia with populations increasing in many vineyards in recent years. Economic damage is caused primarily to the berries although secondary problems such as fruit rots of injured berries also occur. This species overwinters as pupae in grayish silken cocoons in fallen leaves. Research in Virginia indicates three to four generations per year, with a possible fifth in some seasons. Adults emerge after 10-14 days, peaking in mid-August to feed on fruits and foliage.
Monitoring: Populations of grape berry moth may be monitored with a commercially available pheromone trap. However, the relationship between trap captures and damage is strongly influenced by vineyard surroundings. In vineyards surrounded by open terrain (cornfield or pasture, etc.), trap numbers may be high but actual injury low. In vineyards surrounded by woodland (with wild grapevines), trap captures may be low, but accompanied by high levels of injury.
Chemical Control: Several chemical options are available for the control of GBM (see rate data below). These include azinphos-methyl, phosmet, and methoxychlor. The latter, however, is inadequate where pest pressure is high.
Alternative Control: Mating disruption (Isomate-GBM) is registered for GBM and should be used at the full labeled rate. However, effectiveness may be limited due to edge effects in smaller vineyards.
Biological Control: An egg parasite, Trichogramma minutum Riley, provides some biological control against the GBM.
Cultural Control: In areas where GBM feeding has been severe several cultural control options are available. These options include (1) leaves may be raked and burned in the fall, (2) the soil beneath rows may be cultivated to bury overwintering pupae, and (3) soil from row centers can be piled beneath vines to trap pupating larvae, and subsequently be plowed/disked. However, none of these are economically feasible.
Yellowjackets, Vespula spp.
Yellowjackets and certain other wasps may break open the skins of grape berries in order to reach the sweet contents. In the early part of the growing season these wasps are mainly predatory. However, toward the end of the season the wasps' foraging behavior changes as the sugar content of the fruit increases. Once yellowjackets pierce the skin, the fruit become vulnerable to attack by other insects such as honeybees and fruitflies which are also drawn to the sweet contents.
Chemical Control: The establishment of bait stations in early spring, containing an attractant and a pesticide provide direct control against overwintering yellowjacket queens.
Cultural Control: Destruction of nearby yellowjacket nests is helpful but difficult, because the nests are often difficult to locate.
European red mite, Panonychus ulmi (Koch)
The European red mite (ERM) can be a major pest within vineyards in Virginia, causing extensive injury if uncontrolled. Damage results primarily from foliage feeding, which destroys chlorophyll, reduces respiration, and decreases the ability of the leaf to produce photosynthates. Lack of photosynthate can result in a reduction in fruit size and also fruitfulness the following season. Typically, overwintering eggs are fertilized and deposited, in groups, on the roughened bark area around buds and fruit spurs in early to mid-August. Egg hatch occurs in correlation with bud development the following spring, and continues through bloom. Once hatched, the larvae immediately begin feeding on the foliage and often develop into adults by bloom time.
Monitoring: During the dormant period and up to early bloom, vines can be evaluated for overwintering ERM eggs, with careful attention being paid to typical egg deposition sites. If a prebloom treatment was applied, then the first sample for motile mites can usually be delayed until early to mid June. If no preventative applications were used prior to bloom, evaluation of the percentage of mite-infested leaves should begin during the bloom period.
Chemical Control: Acaricides should be applied only if mites exceed 10/leaf (20/leaf on labrusca types), and more than minor bronzing occurs. Rotation of acaricides is important to prevent resistance development.
Alternate Control: Oil treatments are typically sprayed as bud development begins to prevent the hatching of overwintering ERM eggs.
Superior Oil-Applied only where ERMs are a problem. Should not be applied at an air temperature higher than 85° F or lower than 35° F.
Biological Control: Natural predators of the ERM include Stethorus punctum (Leconte) larvae and adults. The population size of this predator is important for adequate control. Predator mites are usually able to keep ERM populations in check; however this is not always the case within Virginia vineyards.
Chemical Insect Controls
The pesticide use and pest severity study completed on grapes during 1990 and 1991, found that insecticides were used by 93% of growers on an average of 695 total acres (7). At present, this is the most current information available. The growers surveyed (see results under individual descriptions) used the majority of chemicals listed below. In addition, the survey indicated that 6.0% of the acres were treated with methyl parathion at a rate of 0.32 lb. a.i./acre; Bacillus thuringiensis was used on 2.0% at 0.29 lb. a.i./acre; superior oil was used on 1.0% at 2.00 lb. a.i./acre; phosalone was used on 0.1% at 0.13 lb. a.i./acre.
Disease descriptions were modified from the Penn State University Grape Factsheets (8).
Chemical control recommendations were taken from the 1999 Horticulture & Forest Crops Pest Management Guide (6).
In growers’ opinions the most severe grape diseases in Virginia were crown gall, Botrytis bunch rot, black rot and powdery mildew (see descriptions below) (7). Anthracnose, Elsinoë ampelina; downy mildew, Plasmopara viticola; Eutypa dieback, Eutypa lata; Phomopsis cane and leaf spot, Phomopsis viticola, sour rot; Pierce’s Disease, Xylella fastidiosa;tomato ringspot, stem necrosis; black measles; grapevine yellows and two unidentified diseases were also present within the vineyards surveyed. The grapevine yellows disease is currently one of the most severe problems for Virginia Chardonnay producers.
Crown Gall, Agrobacterium tumefaciens
The crown gall disease is caused by the soil-borne bacterium, Agrobacterium tumefaciens.. The crown gall bacterium is systemically present in a vast majority of grape vines, but seldom causes disease unless the vine is injured. In the event that injury does occur, galls can develop rapidly, completely girdling a young vine in one season. When galls are numerous or when they are located on major roots or on the root crown, they disrupt the translocation of water and nutrients, leading to poor growth, gradual dieback, and sometimes death of the vine. In general, affected plants are more susceptible to adverse environmental conditions, especially winter injury.
Chemical Control: Chemical sprays are not effective on Agrobacterium tumefaciens.
Cultural Control: Given that chemical sprays are ineffective on the soil-borne crown gall bacterium, cultural practices such as the pruning of diseased tissues are extremely important in the management of this disease. However, plant wounding caused by budding, grafting, or cold injury can provide suitable conditions for infection by the persistent bacterium. Practices that minimize the risk of wounding, especially those that promote winter hardiness will help protect against crown gall disease. The use of multiple trunk vines and the yearly replacement of dead trunks with renewals also helps to manage the disease at a tolerable level. Certain cultivars such as Vitis labrusca are more resistant to crown gall than Vitis vinifera and may fair better against the disease.
Botrytis Bunch Rot, Botrytis cinerea
The fungus, Botrytis cinerea, causes one of the most common diseases of grapes in Virginia. Most often associated with the decay of ripe or nearly ripe grapes, fruit rot can affect petals, flower stalks, fruit caps and fruit. Susceptibility of these plant parts increases as weather conditions become moist. Fruit infections first appear as soft, light brown areas, eventually resulting in mummification of the fruit. Mummified fruit becomes covered with a dusty powder, through which the infection continues to be spread. The bunch rot phase of the disease causes the greatest economic losses especially on French hybrids and Vitis vinifera cultivars.
Chemical Control: Preharvest fungicide applications are recommended. Well-timed sprays of an effective fungicide are important, especially if weather is relatively wet between veraison and harvest. Earlier sprays will reduce the number of infected flower parts and the amount of young fruit infection.
Cultural Control: Canopy management practices, which improve air circulation in the vineyard and reduce humidity within the canopy are beneficial (i.e. pruning, avoiding excess nitrogen use, proper site selection, etc.). Also, techniques to reduce skin cracking or skin punctures near harvest will help to control ripe fruit rot. Botrytis rot resistant grape cultivars should be planted when possible.
Black Rot, Guignardia bidwellii (Ellis)
Black rot, the disease caused by the fungus Guignardia bidwellii is one of the most serious diseases of grapes in the eastern U.S. This fungus can infect all green parts of the vine including, shoots, leaves, and tendrils, however, the most damaging effect is on the fruit.
Chemical Control: In vineyards with susceptible cultivars or where black rot was a problem the previous year, early season fungicide sprays should be timed to prevent the earliest infections. Black rot management using fungicides for black rot control are either used as protectants or applied after an infection has occurred.
Cultural Control: Sound vineyard sanitation practices will reduce the amount of inoculum present in the following year. Pruning to promote air flow is also beneficial as are resistant cultivars. These should be planted if at all possible.
Powdery Mildew, Uncinula necator
Powdery mildew, caused by the fungus Uncinula necator, is frequently found within vineyards in Virginia. Powdery mildew affects all green tissues and can be found mostly on the leaves and fruit stems, often appearing as white, powdery patches. Fruit infections may also occur, resulting in poor fruit set, fruit shelling and/or a reduction in wine quality on varieties intended for that use.
Chemical Control: For effective management of this disease, sprays may be required as early as 1 to 2 inches of shoot growth on some cultivars (depending on rain and temperature) and should not be delayed beyond the immediate prebloom stage on any vine.
Cultural Control: Planting vines in sites with good air circulation and sun exposure can help to reduce disease severity. Also, use a training system that allows good air movement through the canopy and prevents excess shading.
Chemical Disease Control
The 1990-91 pesticide use and pest severity study found that 97% of growers used fungicides on an average of 695 total acres (7). This class of pesticides was applied most often followed by insecticides>herbicides>alternative controls>nematicides. The surveyed growers (see results under individual descriptions) used the majority of chemicals listed below. In addition, basic copper sulfate was used on 18.5% of the acres treated at an average rate of 3.80 lb. a.i./acre, copper hydroxide was used on 0.2% at 8.00 lb. a.i./acre, copper oxychloride sulfate was used on 3% at 2.00 lb. a.i./acre and dinocap was used on 0.4% at 0.50 lb. a.i./acre. Copper fungicides are typically used for the control of downy mildew.
Cultural Disease Control
Disease resistant cultivars are available for control against certain pathogens. Use of certified vines at planting will ensure the initial health of the vineyard. Mowing or otherwise reducing undergrowth near vines will improve air movement and should help to alleviate mold and mildew problems. Vineyard sanitation practices such as timely harvesting, and the removal of leftover fruit at the end of the season help fruit rots the next year. Also avoiding excess late-season fertilizing can reduce both disease and the possibility of winter injury to cordons and trunks of vines.
Control recommendations were taken from the weed section of the 1999 Pest Management Guide for Horticultural and Forest Crops (6).
Vineyard production systems usually consist of sod row middles alternating with vine rows or trellises. Weeds in the row middles are managed primarily through mowing, however, within rows, herbicides are used. Perennial weeds such as goldenrod, red sorrel, broomsedge, johnsongrass and bermudagrass are common in Virginia. Herbicide usage in this case must be directed to the base of the vine to avoid burning on the leaves and shoots of the plant. If weed control is not maintained within the rows, competition for water and nutrients may reduce productivity of the vines.
The most common weed species found within Virginia vineyards include yellow nutsedge, annual morningglory species, bindweed species, cocklebur, horsenettle, jimsonweed, dandelion, bermudagrass, quackgrass, and wild garlic (9).
Chemical Weed Control
The pesticide use and pest severity study completed on grapes during 1990 and 1991, found that herbicides were used by 75% of growers on an average of 695 total acres (7). The surveyed growers (see results under individual descriptions) used the majority of chemicals listed below. The remaining chemicals (those not included in the survey) may recently have been registered for use on grapes and/or recommended by extension specialists.
PREEMERGENCE HERBICIDES: (used prior to soil emergence of weed seedlings)
POSTEMERGENCE HERBICIDES: (used following soil emergence of weed seedlings)
Portions of the following section as well as the control recommendations were taken from the Mid-Atlantic Winegrape Grower’s Guide (4).
Birds
Many species of birds are fond of ripe grapes and will quickly cause appreciable crop loss if not controlled. Evidence of bird feeding includes peck marks in individual berries, remnants of berry skins retained in the cluster stem, and selective feeding on individual berries of the cluster, leaving the stem intact. Options to control bird feeding are limited (cultural controls only) and very few are entirely effective. Eventually most birds will overcome their aversion to the recommended control methods.
Cultural Control: Scare tactics are the primary type of bird control available. These include noise makers, electrical wires mounted in the vineyard, and simulated bird predators. Vines under or close to roosting areas are the most vulnerable therefore avoiding these areas may provide some control against bird depredation. In situations where total, environmentally benign control is desired, bird netting can be used.
White-tailed Deer, Odocoileus virginianus
One of the most well known mammals in North America, the white-tailed deer is commonly found within vineyards in Virginia. Deer cause damage browsing on the rachises, shoot tips, and leaves, thereby reducing vine health and productivity. Deer also feed on ripening grapes within the vineyard, but may be deterred by various scare tactics. Once deer have learned about a source of food, it will be exceedingly difficult to discourage them. Therefore, early detection and management strategies are critical for deer control.
Chemical Control: Taste and odor repellents are available to deter deer presence within a vineyard, with effectiveness depending on population size, other deer food sources and weather. These chemicals may become expensive if repeated applications are necessary, (i.e. following every rain event). Repellents are generally applied during the dormant season either as aerial, ground or spot treatment application. In addition to the products listed below, deodorant soap, animal tankage and human hair have been used to ward off deer, especially within young trees.
capsaicin (Hot Sauce Animal Repellant)-Applied as an aerial spray during the dormant period. Must be used in combination with Vapoguard (2.00 qt./gal. of water) at a rate of 6.00-8.00 oz./gal. of water. Both mixtures should be added to water to obtain a total volume of 100 gal.
hinder (Hinder Deer)-Active ingredients (13.8%) include ammonium salts of C8-18 and C18’ fatty acids, ammonium soaps of fatty acids, and phenol, 2,4-dichloro-benzenesulfonate. May be applied during the growing season or dormant period at a rate of 3.00-5.00 gal./100 gal. of water (ground) or 3.00-5.00 gal/5-10 gal. of water/acre (aerial) to deter deer feeding.
Cultural Control: Hunting licenses or special permits may be obtained to decrease population size. Trained dogs confined by invisible fencing as well as noise emitters may also be used to reduce the presence of deer within a vineyard. Various forms of electric and non-electric fencing are available for prohibiting deer entry into vineyards. Combinations of these control techniques are usually more effective than any form used alone.
C&P Press Online Crop Protection Reference
North Carolina Information for Small Fruits
Office of Pest Management Programs/Pesticide Impact Assessment Program Site
Penn State Fruit Pathology Factsheets
Virginia Pesticide Impact Assessment Program
Virginia Tech Pesticide Programs
Prepared by:
Donna M. Tuckey
Graduate Assistant
Virginia Polytechnic Institute & State University
Department of Entomology
Virginia Tech Pesticide Programs-0409
Blacksburg, VA 24061
Ph: (540)-231-6543
Fax: (540)-231-3057
e-mail: dtuckey@vt.edu
Contacts:
Anton B. Baudoin
Extension Plant Pathologist
Virginia Polytechnic Institute & State University
Department of Plant Pathology, Physiology & Weed Science-0331
Blacksburg, VA 24061
Ph: (540)-231-5757
Fax: (540)-231-3221
e-mail: abaudoin@vt.edu
Jeff F. Derr
Extension Specialist, Weed Science
Hampton Roads AREC
1444 Diamond Spring Road
Virginia Beach, VA 23455
Ph: (757)-363-3912
Fax: (757)-363-3950
e-mail: jderr@vt.edu
Doug G. Pfeiffer
Extension Entomologist, Tree Fruits
Virginia Polytechnic Institute & State University
Department of Entomology-0319
Blacksburg, VA 24061
Ph: (540)-231-4183
Fax: (540)-231-9131
e-mail: dgpfeiff@vt.edu
Michael J. Weaver
Extension Pesticide Coordinator
Virginia Polytechnic Institute & State University
Department of Entomology
Virginia Tech Pesticide Programs-0409
Blacksburg, VA 24061
Ph: (540)-231-6543
Fax: (540)-231-3057
e-mail: mweaver@vt.edu
Tony K. Wolf
Viticulture Extension Specialist
Winchester AREC
595 Laurel Grove Rd.
Winchester, VA 22602
Ph: (540)-869-2560
Fax: (540)-869-0862
e-mail: vitis@mail.vt.edu
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.