Crop Profile for Labrusca Grapes in Pennsylvania

Prepared Feb, 2002

Although Pennsylvania produces less than 1% of the total US grape crop, the Commonwealth produces 10.8% of the US grape crop that is utilized for grape juice. In 2000, the state harvested 46,000 tons of juice grapes at a value of $11.8 million. The vast majority of these grapes are grown in Erie county in the extreme northwestern corner of Pennsylvania.

The state’s 265 native (Catawba, Concord, Delaware, Fredonia, Niagara) variety grape growers maintain over 10,800 acres of vineyards. Approximately 90% (9773 acres) of that total is Concord variety grapes grown in Erie county. Another 5.3% (575.7 acres) of that total is Niagara variety grapes grown in that same county. Less than 1% of the states native variety grapes are grown elsewhere in Pennsylvania. For that reason, this profile will focus on Niagara and Concord variety grape production in that region of the state.

The use of pesticides in the production of Labrusca grapes is minimized due to several factors. Labrusca grapes enjoy a smaller insect pest complex than other fruit crops and are less susceptible to these pests when compared to V. vinifera and French Hybrid varieties. Like many other crops, processed grapes have a higher tolerance for cosmetic defects caused by insects and diseases than those grapes that will be consumed fresh. In addition to label restrictions, processors sometimes put restrictions on pesticide use. For example, Welch’s (the largest market for PA juice grape producers) has forbidden the use of Captan grapes in the production of grapes sold to their company. Finally, the relatively low per unit value of juice grapes (when compared to wine or table grapes) helps to drive producers to integrated pest management practices and other alternatives to chemical pesticides.

Despite these factors, pesticides are an essential part of the Pennsylvania grape producer’s pest management efforts. Recent actions including the loss of benomyl, methyl parathion, and azoxystrobin (Erie County PA Only) have made resistance management, protection of beneficial insects and the preservation of existing chemical pest management tools increasingly important.

Angular Leaf Scorch

Type of Pest: Disease

Frequency of Occurrence: Angular leaf scorch is most likely to become a problem when high rainfall occurs during the period of early shoot growth.

Damage Caused: Disease symptoms occur mainly on the leaves and first appear as faint chlorotic spots. Lesions enlarge and change from yellow to reddish-brown, eventually killing the tissue. Lesions are confined by major veins and can have a yellow, red, or absent margin. Infected leaves often fall prematurely.

% Acres Affected: 35%

Pest Life Cycles: The fungus survives winter in infected leaves on the vineyard floor. Mature spores are ready for discharge in spring when grape buds begin to grow. During rainfall, spores are released into the air from fruiting structures and susceptible tissue is infected.

Timing of Control: Fungicides should be applied prior to rainfall, beginning at the 3-inch stage and continuing through fruit set. Angular leaf scorch is typically only a problem during years with extremely wet springs.

Yield Losses: Premature loss of leaves is detrimental to sugar accumulation in berries but is more detrimental to overall vine health in cold sensitive varieties.

Cultural Control Practices: Cultural practices that increase air circulation can reduce duration’s of leaf wetness that favor disease development. Destruction of leaf litter by cultivation, before bud break, can also reduce disease incidence.

Biological Control Practices: None available at this time

Post-Harvest Control Practices: None

Other Issues: There is no currently labeled fungicide to control this disease. However, mancozeb utilized to control other diseases on grapes will control angular leaf scorch.

Black Rot

Type of Pest: Disease

Frequency of Occurrence: 3- to 5-inch shoot growth through approximately August 1

Damage Caused: Black rot is one of the most serious diseases of grapes in the eastern United States. This disease can cause substantial crop loss under the appropriate environmental conditions. All green tissues of the vine are susceptible to infection.

% Acres Affected: 40%

Pest Life Cycles: The black rot fungus overwinters primarily in mummified fruit on the vineyard floor or fruit retained within the vine. It can also overwinter within cane lesions. Spores within cane lesions are available for infection starting at bud break; however, the vast majority of spores (those within mummified fruit) first become available about 2-3 weeks after bud break, then reach peak levels from about 1-2 weeks before bloom until about 1-2 weeks after, depending on the year. Rain triggers the release of infective spores from mummies, and infection occurs if susceptible tissues remain wet for a sufficient length of time, which depends on temperature. Pycnidia develop within lesions caused by current season infections and release a new crop of spores during the summer. It is this secondary round of spore release and infection that is responsible for the majority of fruit rot damage. Thus, if very few current season infections are present, protective sprays can usually be stopped once most of the overwintering inoculum has been depleted (about the time berries become pea-sized). However, if more than a few current infections (and new spores) are present, protection must be maintained until fruit begin to ripen.

Timing of Control: Disease severity the previous year and varietal susceptibility to black rot are the major factor in determining how early protection is required. Under heavy disease pressure protectant application could begin as early as 3-inch shoot growth on susceptible varieties. However, the two most important sprays are the immediate prebloom and 10 to 14-days later at the immediate postbloom.

Yield Losses: 50% in years of frequent early rainfall which favors development of primary infections.

Cultural Control Practices: Removal of mummified clusters during pruning significantly reduces disease pressure for the coming season; spring cultivation to bury mummies also can contribute to a reduction of inoculum. Cultural practices that open the canopy are beneficial because they increase air circulation and improve spray coverage.

Biological Control Practices: None available at this time

Post-Harvest Control Practices: Removal of mummified berries during pruning

Other Issues: Many of the fungicides currently available for use provide control of more than one disease. Although azoxystrobin is labeled for use in controlling black rot, Erie County Pennsylvania is excluded from the label due to problems with phytotoxicity to apples. Mancozeb and maneb + zinc salt materials provide protection against black rot, downy mildew and Phomopsis Cane and Leaf Spot while myclobutanil (Nova), provides protection against both black rot and powdery mildew. While any one chemical may be sprayed up to 3 times during the growing season for black rot, it is more common to see a single application of a variety of materials depending on the primary disease targeted for that particular application. In general no more than 3 applications of pesticide are used for black rot protection in a normal year and a majority, if not all, of the applications are applied for protection of other diseases as well. The use of mancozeb and maneb + zinc salt materials are banned by Lake Erie Processors once bloom begins in an attempt to eliminate residues of these materials at harvest.

Chemical Controls:

Downy Mildew

Type of Pest: Disease

Frequency of Occurrence: 10-inch shoot growth to harvest

Damage Caused: Berries, leaves and young shoots can be infected. This can result in a loss of growth with early season shoot infection, premature defoliation with leaf infections and direct crop loss through berry infections.

% Acres Affected: 35%

Pest Life Cycles: The downy mildew fungus overwinters as dormant spores within infected leaves on the vineyard floor and first becomes active in the spring about 2-3 weeks before bloom (at approximately 10-inch shoot growth). Infective spores are then produced during rainy periods if temperatures are above 50 F, and are splashed onto susceptible tissues to cause the season’s first (primary) infections. (Note that inoculum for such early-season infections comes from within the vineyard.) Epidemic disease development can then result from repeated cycles of secondary spread, which is caused by new spores produced within the white fungal growth on infected tissues. These spores are produced only at night when the relative humidity is extremely high (>95%). They can be blown relatively long distances and cause infection when they land on susceptible tissues that remain wet. (Note that later-season disease spread can be regional.) Thus, disease spread is most severe during periods when humid nights with moderate to warm temperatures (which allow the secondary spores to form) are followed the next day by rains or thundershowers (which allow them to germinate and cause new infection).

Timing of Control: 10-inch shoot growth through harvest, depending on frequency of early season rainfall, varietal susceptibility and overwintering inoculum.

Yield Losses: Can be 90% if early season infections to shoots, leaves and /or clusters are not controlled.

Cultural Control Practices: Any practice that improves air circulation and speeds drying within vine canopies will help to control downy mildew. Spring cultivation to bury fallen, infected leaves from the previous year will also help to reduce early season disease pressure. However, properly timed fungicides are still necessary for reliable disease management.

Biological Control Practices: None available at this time

Post-Harvest Control Practices: None available at this time

Other Issues: Although azoxystrobin is labeled for use in controlling black rot, Erie County Pennsylvania is excluded from the label due to problems with phytotoxicity to apples.

Chemical Controls:

Eutypa Die Back

Type of Pest: Disease

Frequency of Occurrence: Spores are available during winter during rainfall or snow melt events.

Damage Caused: Eutypa dieback produces cankers in the cordons, or trunks, of a vine which slowly caused portions of the vine above the canker to die. The entire vine, or portions of the vine can be affected.

% Acres Affected: 80%

Pest Life Cycles: In winter, during rainfall or snow melt, fungal spores are released from fruiting structures on dead infected wood. Spores are dispersed by the wind and infection occurs when they enter fresh pruning wounds. Cankers and foliage symptoms are not evident until two to four years after infection; then vine deterioration continues until the trunk or arm is finally killed. New shoots above cankers often appear stunted, with shortened internodes and small, cupped, greenish-yellow leaves in the spring. Healthy growth usually overgrows and obscures affected shoots by midsummer. Shoot and leaf symptoms become progressively worse each season until, eventually, no growth is produced.

Timing of Control: There is no chemical control with the loss of Benlate.

Yield Losses: Loss of vines due to infection can cause significant loss of crop if disease is not caught early and controlled.

Cultural Control Practices: Infected arms and trunks should be removed in late spring when foliar symptoms are noticeable and wounds are less susceptible to reinfection. Pruning should be far enough below the canker that healthy wood is evident. Any infected wood or stumps should be removed from the vineyard and burned.

Biological Control Practices: None available at this time

Post-Harvest Control Practices: None

Phomopsis Cane and Leaf Spot and Fruit Rot

Type of Pest: Disease

Frequency of Occurrence: 1-inch shoot growth through immediate post bloom Shoot lesions can produce inoculum for a period of 5 to 7-years.

Damage Caused: All green tissues of the vine are susceptible to infection. Severely infected leaves are misshapen, yellow, and fall from the vine prematurely. Infected rachises are brittle so that portions of the cluster may fall off before harvest. Infected fruit are discolored and can drop to the ground before maturity.

% Acres Affected: 85%

Pest Life Cycles: Rainy weather during the early growing season favors disease development. Spores (pycnidiospores) are produced within the black fruiting bodies (pycnidia) and ooze out during wet weather. These spores are then splashed by the rain onto newly developing shoots. Shoot tips may become infected at any time during the year, but infection is more common between bud break and bloom. Shoot and leaf lesions typically appear 3 to 4 weeks after infection. Infection of the rachis can occur from the time clusters are first visible, when shoot growth measures 2- to 3-inches, through fruit set. Fruit becomes infected at or shortly after bloom, but the fungus remains latent until the fruits ripen. Symptoms of fruit rot and most rachis lesions begin to appear 1 to 3 weeks before harvest. Infected leaves may not develop symptoms until they become senescent. Some infections of the shoot may never develop symptoms but will produce pycnidia during the dormant season. The fungus overwinters on the vine in infected canes and rachises and may survive and sporulate in dead infected canes for more than one season. Spores from pycnidia are produced in the spring to renew the disease cycle.

Timing of Control: The critical period for development of the cane and leaf spot phase of the disease is during the first few weeks of growth (starting at 1-inch shoot growth). Rachises are susceptible from the time clusters first become visible until after pea-sized berries are formed. Fruit are most susceptible from bloom until after pea-sized berries are formed.

Yield Losses: When incidence of the disease is high, crop losses of 10 to 30 percent can occur.

Cultural Control Practices: None available

Biological Control Practices: None available at this time

Post-Harvest Control Practices: Removal of infected wood during dormant pruning. In cases of severe infection this method of control is not practical as the integrity of the training system would be compromised due to removal of canes used in the structure of the vine.

Other Issues: The use of Captan has been banned by Lake Erie region grape processors, while the use of mancozeb and maneb + zinc salt materials are limited by Lake Erie Processors to the prebloom period only in an attempt to eliminate residues of these materials at harvest.

Chemical Controls:

Powdery Mildew

Type of Pest: Disease

Frequency of Occurrence: 1-inch shoot growth through approximately August 1

Damage Caused: The powdery mildew fungus can infect all green tissues of the grapevine. It appears as a white or grayish-white powdery covering on the upper and lower surfaces of leaves and fruit. Expanding leaves that are infected become distorted and stunted. When green shoots are infected, the fungus appears dark brown to black and remains as brown patches on the surface of dormant canes. Cluster infection before or shortly after bloom may result in poor set and considerable crop loss. If berries are infected when they are pea-size or larger, the epidermis stops growing but the pulp continues to expand and the berry splits. When berries of purple or red cultivars are infected as they begin to ripen, they fail to color properly and have a blotchy appearance at harvest. Such fruit will produce wines with off flavors.

% Acres Affected: 100%

Pest Life Cycles: The powdery mildew fungus overwinters as cleistothecia on dead leaves and bark. Shortly after bud break, cleistothecia swell under moist conditions and break open, releasing the ascospores contained within. The ascospores may then cause infections on all green tissue. Lesions resulting from ascospore infections produce conidia, which spread the disease. Wind-borne spores (conidia) are produced abundantly on the infected tissue and spread the disease to neighboring vines. As adjacent leaves and flower clusters become infected, new conidia are produced on them and the disease can spread rapidly throughout the vineyard. In late summer the powdery mildew fungus produces black spherical bodies (cleistothecia) on the surface of the infected leaves, shoots, and berries.

Timing of Control: 1-inch shoot growth through late summer. One-inch spray is for highly susceptible varieties or problem areas if the weather forecasts call for rain and temperatures above 50°F.

Yield Losses: Severe, early season infections can result in 20% crop loss as the cells in the skin of the berry are killed and lose the ability to expand. This results in cracked berries which can lead to secondary infections by molds and other mildews.

Cultural Control Practices: Any practice that improves air circulation and thereby reduces humidity within the canopy is of significant benefit.

Biological Control Practices: None available at this time

Post-Harvest Control Practices: None available at this time

Other Issues: Many of the fungicides currently available for use in Pennsylvania vineyards provide control of more than one disease. Due to the risk of development of resistance to powdery mildew by the newer classes of fungicides, resistance management strategies have been developed which promote the integration of several fungicides with different modes of action to be used during each growing season. Alternating different modes of action is recommended to delay resistance development. Fungicides are applied before infection as protectants.

Chemical Controls:

Banded Grape Bug

Type of Pest: Insect

Frequency of Occurrence: Sporadic pest of grapes. When present damage occurs between mid-May and early June

Damage Caused: Feeding injury results in floret drop, reduced berry set, and reduced cluster number

% Acres Affected: 10%

Pest Life Cycles: Nymphs of this insect emerge in the spring and feed, using their sucking and piercing mouth parts, on flowers and young berries. Injury by small nymphs, occurring between 3- to 5-inch shoot growth (around May 15) and early June, results in floret drop, reduced berry set, and reduced cluster number. Subsequent feeding by larger nymphs and adults does not affect cluster development. This injury only occurs in the early prebloom stages (between 5- and 10-inch shoot growth). Subsequent feeding by nymphs does not reduce berry set. Adults appear to be predaceous and do not cause injury to berries. This pest is sporadic and does not require treatment in most years.

Timing of Control: 3- to 10-inch shoot growth

Yield Losses: Up to 100% reduction in area infested by this pest through loss of florets. Reduction of crop size of 50% is typical when banded grape bug exceeds the economic threshold of 1 nymph per 10 shoots.

Cultural Control Practices: None available

Biological Control Practices: None available

Post-Harvest Control Practices: Not applicable

Other Issues:

Chemical Controls:

Climbing Cutworm

Type of Pest: Insect

Frequency of Occurrence: Sporadic pest of grapes. Cool springs which delay buds moving from bud swell to shoot growth favor injury by this pest.

Damage Caused: Feeding results in the loss of primary and in some instances loss of secondary and tertiary buds. Grapevines do compensate, at least to some extent, for primary bud loss through production of secondary buds. However, shoots from such buds are less fruitful than those from primary buds. When both primary and secondary buds are damaged the tertiary buds produce only a shoot but no fruit.

% Acres Affected: 5%

Pest Life Cycles: Larvae feed on the buds from full bud swell through bud break and until shoots are 10 to 15 cm long. Larvae hide during the day under the bark and in the soil litter beneath a vine and come out at night to feed.

Timing of Control: Bud swell

Yield Losses: In areas with high levels of feeding activity 30% crop reduction can occur. This pest can severely impact newly planted vineyards by destroying buds and delaying, or eliminating, shoot development needed to produce the necessary training systems.

Cultural Control Practices: Maintaining a vegetation-free band under the row can reduce habitat needed by the climbing cutworm to hide during the day.

Biological Control Practices: No alternatives have been shown to be viable at this time.

Post-Harvest Control Practices: Not applicable

Other Issues:

Chemical Controls:

European Red Mite

Type of Pest: Araqchnid

Frequency of Occurrence: Sporadic to yearly pest of grapes depending on location.

Damage Caused: Given a head start, the vine can tolerate a fair amount of feeding damage on lower leaves. If mites get out on the shoot tips early in the season, however, they can stunt shoot development. Heavy mite infestations (20 to 30 mites per leaf) early in the season can cause stunted, chlorotic shoots with small leaves and pinpoint necrotic areas on leaves. Later in the season, as shoot growth rate declines and the vine allocates more resources to fruit, mites may also have an increased capacity to cause damage.

% Acres Affected: 5%

Pest Life Cycles: Mites overwinter as eggs on the bud scales. Nymphs appear very early in the growing season and pierce the leaf cells to extract plant juices. Both nymphs and adults feed on grape leaves. European red mite can have four to nine generations per year depending on weather conditions.

Timing of Control: Particular attention should be paid to the 1- to 4-inch shoot growth stage and immediate to 20 days postbloom. Vines should be monitored for the presence of this pest and acaricides applied if populations are over the economic threshold for that scouting period.

Yield Losses:

Biological Control Practices: Predatory mites, when present in the vineyard at sufficient densities, can provide excellent biological control of spider mites. Recent research indicates that frequent use of mancozeb fungicides (a common fungicide in vineyard disease management programs) reduces predatory mite populations.

Post-Harvest Control Practices: Not applicable

Other Issues:

Chemical Controls:

Grape Berry Moth

Type of Pest: Insect

Frequency of Occurrence: There are three to five generations of this pest every year. Grape Berry Moth is one of the most serious insect pests affecting grapes in Pennsylvania.

Damage Caused: Direct feeding on clusters by larvae during the bloom period. After berries have developed, larvae enter berries and feed within. Late season feeding results in damage to multiple berries per clusters as berry enlargement causes berries to touch each other facilitating movement of a single larvae from berry to berry within a cluster.

% Acres Affected: 90%

Pest Life Cycles: Overwintered pupae emerge as adult moths in late May and lay eggs among the grape clusters. The larvae are small (up to 0.38 inch long) and feed internally in grape berries. The larvae cut flaps in grape leaves and pupate inside, emerging as adult moths (wingspan is 0.5 inch). Three to five generations of this pest can occur each season depending on length, and heat accumulation, of growing season.

Timing of Control: Timing of sprays is currently determined using the Grape Berry Moth Risk Assessment protocol and scouting. Timings could include: 10 days post bloom, first week in August and first week in September. Applications are made using the Grape Berry Moth Risk Assessment Protocol developed by Hoffman and Dennehy. The Risk Assessment Protocol is detailed in Bulletin No. 138. Risk Assessment for Grape Berry Moth and Guidelines for Management of the Eastern Grape Leafhopper. This bulletin can be found on line at: http://www.nysaes.cornell.edu/ipmnet/ny/fruits/grapes/grmanfs/risk.pdf

Yield Losses: Load rejection due to grape berry moth found in excess of Federal inspection standards is a major concern. Percent crop loss has not been determined but research has shown 50-80% cluster infestation at harvest is not uncommon and complete crop loss has occured. Vineyards located next to wooded areas, those having prolonged snow cover, and/or vineyards in areas where winter temperatures are mild (i.e. lake plains) are more susceptible to infestation by grape berry moth.

Cultural Control Practices: No feasible cultural control practices are available

Biological Control Practices: While research is being conducted on biological alternatives for grape berry moth no economically feasible alternatives are currently available.

Post-Harvest Control Practices: Not applicable

Other Issues:

Chemical Controls:

Grape Cane Gallmakers

Type of Pest: Insect

Frequency of Occurrence: Early spring

Damage Caused: Gall-like swellings on canes are caused by the oviposition injury. Galls are usually twice as thick as the cane and 2.5 to 4 cm long. In newly planted vineyards gallmaker can destroy canes necessary for developing a training system, resulting in an extra year being necessary before a crop can be harvested from the vine. Galls usually have little effect on vigor and growth of mature vines but they can weaken the mechanical strength of the cane and cause breakage. In cases of severe infestations, shoot length can be severely stunted resulting in the loss of the crop on infested canes and the loss of the shoot for canopy management for next year.

% Acres Affected: 10-15%

Pest Life Cycles: The grape cane gallmakers has only one generation per year.

Timing of Control: 4 to 6-inches of shoot growth

Yield Losses: In newly planted vineyards gallmaker can destroy canes necessary for developing a training system, resulting in an extra year being necessary before a crop can be harvested from the vine. Galls usually have little effect on vigor and growth of mature vines but they can weaken the mechanical strength of the cane and cause breakage. In cases of severe infestations, shoot length can be severely stunted resulting in the loss of the crop on infested canes and the loss of the shoot for canopy management for next year.

Regional Differences: Grape Cane Gallmakers appear to be most common in the part of the county along Lake Erie.

Cultural Control Practices: Removal of infected canes below the galls during dormant pruning. This is not always feasible if infestation was severe or if canes are needed to maintain training system.

Biological Control Practices: None available

Post-Harvest Control Practices: Removal of infected canes below the galls during dormant pruning. This is not always feasible if infestation was severe or if canes are needed to maintain training system.

Other Issues:

Chemical Controls:

Grape Cane Girdlers

Type of Pest: Insect

Frequency of Occurrence: 10 to 12-inch shoot growth.

Damage Caused: The girdling by the female causes the terminal growth of the new shoots to bend over above the upper girdle and drop to the ground. Later the whole infested shoot dies back to the lower girdle and falls from the vine. Vines ‘pruned’ by the grape cane girdler have a ragged appearance suggesting serious injury to the plant. However, the actual damage is usually minor. Girdling of the terminal growth has little or no effect on the crop unless fruit-producing nodes are close to attacked shoot tips.

% Acres Affected: 1%

Pest Life Cycles: Adult beetles emerge from infested canes during August and subsequently overwinter in trash on the ground. In May of the following year the adults leave their overwintering sites. When grape shoots are 30 to 50 cm long, usually in late May, the female begins to lay her eggs and girdle new canes. Egg-laying continues for about one month.

Timing of Control: 10 to 12-inches of shoot growth

Yield Losses: Girdles are generally beyond the last grape cluster, so there is usually no loss of fruit, except in years of heavy infestation.

Cultural Control Practices: Removal and burning of infested canes below the girdle prior to the emergence of adults in late summer.

Biological Control Practices: None available

Post-Harvest Control Practices: None available

Other Issues:

Chemical Controls:

Grape Flea Beetles

Type of Pest: Insect

Frequency of Occurrence: A sporadic pest which does it damage at bud swell. This pest is most damaging in years with cool springs which prolong the time which buds remain in the bud swell to 3-inch shoot growth stage.

Damage Caused: Overwintering adults attack the swelling buds by boring into them and hollowing out the inside. In contrast, the larvae and summer adults feed on the tender leaf tissues but avoid the leaf veins. Feeding on the primary buds is by far the more serious damage by this insect, causing yield loss and stunted growth from secondary or tertiary

% Acres Affected: 5%

Pest Life Cycles: The grape flea beetle is one of the first insect pests to appear in vineyards in the spring. There is only one generation per year. Overwintering adults become active and migrate to the grapevines at about the time grape buds begin to swell. Overwintering adults attack the swelling buds by boring into them and hollowing out the inside. Eggs are placed on the hardened scales surrounding the buds, but most are laid under the loose bark of the canes and near the buds. As foliage develops some eggs are laid on the upper side of the leaves but none are deposited on the underside. The larvae and summer adults feed on the tender leaf tissues but avoid the leaf veins.

Timing of Control: Bud swell

Yield Losses: The amount of yield loss varies from year to year. It is more serious in years when bud development is prolonged by unfavorable climatic conditions. Feeding on the primary buds is by far the more serious damage by this insect, causing yield loss and stunted growth by the secondary and tertiary buds. No fruit develops on canes where the primary and secondary buds were destroyed.

Regional Differences: No regional differences are readily apparent.

Cultural Control Practices: Cleaning up wasteland and woodland areas located near cultivated vineyards eliminates or reduces hibernating sites. Frequent disking to control weeds between grape rows can also break the pupal cells in the soil. However, the practice of disking has been reduced in recent years due to concerns over erosion, poor economics as a weed management method and the need for a firm vineyard floor for various vineyard operations occurring throughout the summer (especially after heavy rainfalls)

Biological Control Practices: None available

Post-Harvest Control Practices: None available

Other Issues:

Chemical Controls:

Grape Leafhoppers

Type of Pest: Insect

Frequency of Occurrence: One to two generations per year depending on growing degree day accumulations. Leafhoppers are present every year at varying levels.

Damage Caused: Both the adults and nymphs feed on the underside of grape leaves by piercing the tissue and sucking out the plant juices. Damaged leaves become mottled with yellow dots. Excessive feeding can result in necrosis of large areas of leaf surface. A moderate infestation of grape leafhopper does not affect yield and quality significantly.

% Acres Affected: 50%

Pest Life Cycles: Adults overwinter in leaves and litter and enter vineyards in the spring and feed on sucker leaves. These overwintered adults generally do not cause serious damage. Depending on growing degree day (heat units) accumulations, one to two generations occur. Rapid population increases are most likely in hot, dry years.

Timing of Control: Timing of control measures is determined using the leafhopper scouting protocol. Control measures are typically timed in conjunction with grape berry moth scouting with insecticide applications specifically for leafhoppers necessary only if an insecticide for grape berry moth is not required.

Yield Losses: Research has shown that the only time significant yield losses (up to 30%) occur are during seasons which are hot (which drives increases in leafhopper populations) and dry enough to put vines under water stress. Moderate to heavy feeding by leafhoppers in a "normal" year can produce a slight decrease in sugar accumulation causing grapes to be harvested later in the season and reducing the time period vines have to recover prior to the first frost.

Regional Differences: Regional differences are not as critical as differences between varieties. Different species of leafhopper are found on Vinifera and Hybrid grapes than on Labrusca-type cultivars. Labrusca-type grapes (i.e. Concord, Niagara, Catawba, Delaware) have Erythroneura comes, also known as Eastern grape leafhopper. Hybrids and Vinifera grapes are infested by other Erythroneura leafhopper species, principally Erythroneura bistrata. This distinction may be important in grape producing areas outside Pennsylvania, where resistance of Eastern grape leafhopper to carbaryl is suspected in isolated vineyards. The species of leafhoppers found on hybrid and vinifera grapes in Pennsylvania are not affected by resistance at this time.

Cultural Control Practices: None available

Biological Control Practices: Research has been conducted using Anagros epos, a wasp which parasitizes leafhopper eggs. This wasp is found in the wild but has not been shown to be effective in keeping leafhopper population below economic levels during years of high infestations.

Post-Harvest Control Practices: None available

Chemical Controls:

Grape Rootworm

Type of Pest: Insect

Frequency of Occurrence: Mid- to late May through July

Damage Caused: Grape rootworm is a beetle that feeds on grape foliage as an adult, producing chain-like feeding patterns on the leaves. Immature stages, however, feed on grape roots, and can cause serious damage and vineyard decline over a period of years if left untreated.

% Acres Affected: 5%

Pest Life Cycles: The grape rootworm produces only one generation per year. During its lifetime, a rootworm will begin as an eggs which is deposited under the bark of grape vines by an adult female. It will spend the following 9 to 10 months of its life in the immature grub stage in the soil feeding on roots, and will spend the ultimate month or so of its life as an adult feeding on grape foliage and laying eggs. The grape rootworm requires at least one year to complete its life cycle.

Timing of Control: An insecticide is applied when the chain-like feeding of the adult is first seen in the vineyard.

Yield Losses: If uncontrolled, root feeding by the immature stage of rootworm can lead to vineyard decline and total crop loss.

Cultural Control Practices: None available

Biological Control Practices: None available

Post-Harvest Control Practices: Not applicable

Chemical Controls:

Japanese Beetles

Type of Pest: Insect

Frequency of Occurrence: Mid-summer

Damage Caused: Damage is caused by direct feeding on the leaves

% Acres Affected: 10%

Pest Life Cycles: This pest overwinters as a larva below the soil surface. During late spring, larvae move closer to the soil surface and complete their development, with the larvae feeding principally on roots. Adults emerge in late-June or early-July and begin feeding on foliage. Mating occurs at this time and eggs are laid in the thatch layer of soil and take approximately 10 days to hatch. Young grubs begin feeding on plant roots and continue to feed until cold weather, at which time they tunnel 3 to 12 inches down into the soil where they construct overwintering cells. There is one generation per year.

Timing of Control: After beetles appear in early to mid-July

Yield Losses: Damage is mostly cosmetic in vigorously growing vines. Excessive foliar feeding in newly planted vineyards can result in delayed root and canopy development resulting in a delay of one year or more in terms of full crop production.

Regional Differences: No regional differences are apparent

Cultural Control Practices: None available

Biological Control Practices: No economically effective biological control is available at this time.

Post-Harvest Control Practices: Not applicable

Other Issues:

Chemical Controls:

Rose Chafer

Type of Pest: Insect

Frequency of Occurrence: Yearly, although severity varies widely from year to year. Feeding is typically confined to the pre-bloom to bloom periods.

Damage Caused: Damage from these insects occurs around bloom from direct feeding on flower clusters and leaves.

% Acres Affected: 5-10%

Pest Life Cycles: Adult rose chafer become active in northeastern North America from late May to early June. The adults appear suddenly with the entire population maturing at approximately the same time. Beetles feed directly on the clusters and leaves and mate soon after emerging from the soil. Females deposit eggs singly a few centimeters below the soil surface. Mating and egg laying occur continuously for about two weeks with each female depositing 24 to 36 eggs. The average life-span of the adult is about three weeks. Approximately two weeks after being deposited, eggs hatch into tiny, white, C-shaped grubs. The larvae feed on the roots of grasses, weed, and other plants throughout the summer, becoming fully developed by autumn. Larvae move downward in the soil as soil temperatures decline and form an earthen cell in which they overwinter. In the spring, larvae return to the soil surface, feed for a short time, and pupate in May. After two weeks in the pupal stage, the adults emerge and crawl to the soil surface to begin their cycle again. There is only one generation per year. (Information from Bulletin 861, Midwest Small Fruit Pest Management Handbook, Ohio State University, 1997.)

Timing of Control: 7 to 10 days prior to bloom or when the first beetles appear.

Yield Losses: 30% crop loss from direct feeding on flowers. In heavy infestation, total crop loss can occur.

Regional Differences: Problems are most severe in vineyards planted in light, sandy soil.

Cultural Control Practices: None available

Biological Control Practices: None available

Post-Harvest Control Practices: None available

Chemical Controls:

Potato Leafhopper

Type of Pest: Insect

Frequency of Occurrence: Sporadic pest of grapes. When present damage occurs between mid-May and early June

Damage Caused: Feeding injury results in floret drop, reduced berry set, and reduced cluster number

% Acres Affected: 10%

Pest Life Cycles: Over-inters in south and migrates annually.

Timing of Control: July-August

Yield Losses: Weakens plant by sucking sap from the plant’s vascular system and injection of a salivary toxin that produces characteristic symptoms including leaves with yellow margins that are cupped downward and dark and light green coloration.

Regional Differences: None

Chemical Controls:

Grape Tumid Gallmaker

Type of Pest: Insect

Damage Caused: Feeding injury results in floret drop, reduced berry set, and reduced cluster number

% Acres Affected: 1%

Pest Life Cycles: It lays its eggs in masses between developing tissues at the bud or shoot tips from early May to mid-September. It is the larvae of this species that causes injury to grape plants. After hatching, the larvae bore into vine tissue and cause a round, reddish gall to form. These galls can develop on leaf tissue or petioles, where they probably do little actual damage to the vine, or the grape clusters, where there is more concern about economic injury. Hence, the greatest concern for this pest is in the early part of the season.

Timing of Control: 3- to 10-inch shoot growth

Yield Losses: Causes <10% yield loss to infected plants.

Cultural Control Practices: None available

Biological Control Practices: None available

Post-Harvest Control Practices: Not applicable

Other Issues: No registered treatment is currently recommended in Pennsylvania.

Broadleaf weeds

Type of Pest: Weed

Frequency of Occurrence: Yearly, throughout the season

Damage Caused: Weeds compete directly with the vine for water and nutrients. Weed growth under the row in vineyards has been shown to be responsible for stunted vine size and crop reduction.

% Acres Affected: 100%

Pest Life Cycles: Variable due to species of broadleaf weed

Timing of Control: Prior to emergence, prebloom

Yield Losses: Up to 30% dependent on species of weeds present and degree of ground surface covered. Reduction in vine size due to competition of weeds for water and nutrients can result in decreased yield capacity over the next several growing seasons.

Cultural Control Practices: The practice of "hilling up" or pushing a berm of soil against the vine and "pulling away", or the removal of the berm, can reduce weed populations under the row. However, these practices are labor intensive and less cost efficient than traditional pesticide based practices.

Biological Control Practices: None available

Post-Harvest Control Practices: Not applicable

Other Issues:

Chemical Controls:

Grasses

Type of Pest: Weed

Frequency of Occurrence: Yearly, throughout the season

Damage Caused: Weeds compete directly with the vine for water and nutrients. Weed growth under, and between, the row in vineyards has been shown to be responsible for stunted vine size and crop reduction.

% Acres Affected: 100%

Pest Life Cycles: Variable due to species of grass

Timing of Control: Prior to emergence, prebloom

Yield Losses: Up to 30% dependent on species of weeds present and degree of ground surface covered. Reduction in vine size due to competition of weeds for water and nutrients can result in decreased yield capacity over the next several growing seasons.

Cultural Control Practices:

Biological Control Practices: None available

Post-Harvest Control Practices: Not applicable

Other Issues:

Chemical Controls:

Profile Prepared By:

Andy Muza
Extension Agent
Erie County - Viticulture
Penn State University

Mike Saunders
Associate Professor
Entomology
Penn State University

Jim Travis
Professor
Plant Pathology
Penn State University

Bill Hoffman
Senior Extension Associate
Manager -- Pest Management Info Center
Penn State University
114 Buckhout Lab
University Park, PA 16802
814-865-1074

1. 1999 New York and Pennsylvania Pest Management Recommendations for Grapes.

2. Weigle, T., et al. New York Crop Profile: Labrusca Grapes in New York.