Insects

Fruit Pests

Grape Berry Moth (Paralibesia viteana): The grape berry moth (GBM) is about 3/8 - 1/4” long and has a broad gray band across the middle of its wings. The larva is grayish-green and about 3/8” long when full grown. Larvae are found in the blossoms, young fruit clusters, and newly-formed berries; later they are found in green and ripening berries. Larvae feeding in the green and ripening berries cause most losses. Infested green berries will be seen to have a maroon coloration on one side, especially where the berry comes closest to or contacts a nearby berry in the same cluster. Such coloration indicates that a larva has fed on one berry, burrowed into another, and connected them with webbing. Ripening berries infested with larvae are detected by the wrinkled, shrunken appearance of the fruit.

Management: Remove wild grape plants from areas adjoining the vineyard. Till between rows to bury overwintering larvae. Pheromone traps are available to monitor onset of activity and pressure. Traps should be placed in the vineyard prior to the onset of GBM activity, usually around bloom. Threshold numbers for these traps have not been verified for New England, but they are useful to determine the onset of GBM activity.

Brown marmorated stink bug (BMSB) (Halyomorpha halys): Adult BMSB are approximately 3/4 inch long and are shades of brown on both the upper and lower body surfaces. They have the typical “shield” shape of other stink bugs, almost as wide as they are long. To distinguish them from other stink bugs, look for lighter bands on the antennae and darker bands on the membranous, overlapping part at the rear of the front pair of wings. Masses of 20-30 eggs are laid on underside of leaves. The 5 nymphal stages range in size from 1/8 - 1/2 inch. Nymphs and adult BMSB feed on many hosts including small fruits, tree fruits, vegetables, ornamentals, and seeded crops such as corn and soybeans. BMSB feeds by puncturing the fruit with piercing/sucking mouthparts, and injecting saliva which allows the insect to suck up the plant material through its mouthparts. Fruit tissue at the point of entry and just below into the flesh, then dies and the rest of the fruit grows around it. This leaves a sunken area on the skin at the point of entry, and browning, dead tissue in the flesh.

BMSB has become a serious insect pest throughout much of the mid-Atlantic states and southern New York. As of 2020, BMSB has not caused economic damage to farms in New England. It is unknown at this time whether there will be one or two generations per year.

Management: Monitor for the presence of BMSB using suitable traps (see appendices for sources).  If found, see pest managment table for recommended materials and rates.

Spotted wing Drosophila (SWD) (Drosophila suzukii): SWD are invasive vinegar flies (fruit flies) that can attack unripened fruit. Female SWD cut into intact fruit with their serrated ovipositor to lay eggs under the skin. This allows larvae of SWD to be present during ripening, leading to a risk of detection in ripe fruit after harvest. During egg-laying and larval feeding, sour rot and fungal diseases can also be introduced, further affecting fruit quality. There is a greater risk of fruit contamination at harvest from SWD compared with native species that lay eggs only in already-damaged and rotting fruit.

Management: SWD do not appear to severely threaten grapes at this time. Thin-skinned grapes may be more damaged than thick-skinned grapes and red grapes may be more damaged than green grapes. If SWD have damaged grapes in previous years, apply insecticides when grapes begin to turn color through harvest. Choose insecticides based on efficacy and preharvest interval. Most insecticides will be made more effective by adding sugar to stimulate SWD feeding.

Foliage and Cane Pests

Grape flea beetle (Altica chalybea): This is a metallic blue beetle about 3/16 - 1/4” long that jumps when disturbed. It is found on swelling buds during the spring. The flea beetles overwinter as adults and emerge during April. They chew holes in the ends and sides of buds that are beginning to swell. Such damage destroys the capacity of a bud to develop a primary or secondary shoot. Once the buds have grown to a length of 1/2” or more, the beetles cannot cause significant injury.

Management: See pest management table for recommended materials and timing.

Grape Phylloxera (Phylloxera vitifoliae): The presence of this soft-bodied insect ( about 1/16” or less in length) is indicated by galls or knob-like protrusions on the underside of leaves. It is found primarily on leaves of Vitis vinifera varieties, especially after bloom. The damage results from new leaves remaining curled and unproductive on the vine.

Management: Plant resistant rootstocks. Remove infected leaves. Spray applications should be made immediately after bloom and again 10 days later. See pest management table for recommended materials and timing.

Grape Leafhopper (Erythroneura comes) and Potato Leafhopper (Empoasca fabae): These soft-bodied, elongated insects about 1/8” long, walk quickly when disturbed and hop when touched. The grape leafhoppers are yellow and white or red and white. The potato leafhopper is light green and has a distinctive side-ways walk. Leafhoppers appear primarily in mid-summer and are found on the underside of leaves, especially young ones. Feeding activity causes white blotches on leaves, leaf curling, and eventual leaf drop.

Management: Sample by examining 25-50 leaves per block.  When populations of leafhoppers build up to 3 or more per leaf, apply an insecticide. See pest management table for recommended materials and timing.

Japanese Beetle (Popillia japonica) and Rose Chafer (Macrodactulus subspinosus): These clumsy, large beetles can feed heavily on the foliage of many different plants. Japanese beetles are a shiny copper color, almost round in shape with legs that tend to stick out. They will play dead when disturbed, dropping to the ground. Rose chafers are very similar behaviorally but dull green in color and more oval in shape. They can be found on both leaves and fruit. The feeding damage to leaves results in skeletonizing of the leaves with only the veins left; injured fruit is unsalable. Japanese beetles are about 1/2” long and copper-colored, with metallic green markings. They feed on grape foliage, skeletonizing the leaves during the mid and late summer. The larvae, or grubs, live in the soil, feeding on roots of grasses.

Management: The beetles can be controlled with sprays of labeled insecticides. Traps are also available which use a sex and/or feeding attractant to capture the adults in a can or plastic bag, but such traps may not provide adequate control. Place traps near, but not in the planting, as traps within a planting may suffer increased localized damage from beetles which are attracted, but do not fall into the trap. See pest management table for recommended materials and timing.

Two-spotted spider mite (Tetranychus urticae): Spider mites are very small (1/50”), insect-like creatures that feed on grape foliage, sucking out plant juices and causing a white stippling or bronzing of the leaves. Under heavy infestations, leaves will turn brown and be covered in a fine webbing. Adults may also move onto the fruit, reducing consumer appeal by their presence. 

Management: There have been some reports that soaking sprays of water applied at relatively high pressure may temporarily suppress mite populations. Foliar applications of broad-spectrum insecticides such as diazinon and Danitol may suppress populations of spider mites, but these materials may also reduce populations of natural predators which feed on the spider mites. Several companies now commercially produce predatory mites which feed on spider mites. These predators can be released in grape plantings and may provide some control of spider mites, but research is needed to determine appropriate release rates and timing. It is important, however, to encourage natural enemies of spider mites by reducing the use of pesticides which may harm natural enemies. See pest management table for recommended materials and timing.

Grapevine Aphid (Aphis illinoisensis): These aphids are dark brown and about 1/32 - 1/16” in length. They appear on young shoots and leaves during summer months. When abundant, aphids prevent proper extension of shoots, expansion of leaves, and development of fruit.

Management: When present, an overhead irrigation system can be used to reduce aphid numbers on the vines. This is not a “tested” method but has been recommended anecdotally. Similarly, spraying with water at high pressure can have the same result: washing the aphids off the vine.

Grape Tumid Gallmaker (Janetiella brevicauda): The grape tumid gallmaker (GTM) is a tiny midge (a type of fly) that lays eggs on developing leaves, stems and fruit clusters, causing large galls that can interfere with fruit development and yield.  There are several generations during the season, but the first generation in the spring is the most problematic. The larvae are well protected within the galls making them difficult to kill with contact insecticides.  The adults only live one day, making it difficult to time insecticide applications. 

Management: Pesticide applications for GTG are not economically prudent unless the infestation is heavy or the vineyard has a history of tumid gall problems. Treatment should be timed to kill adults of the overwintered generation as they emerge. Since adults are difficult to detect, it may be most feasible to base control measures on the first sign of larval entrance into vine tissues or on the first indication of gall formation. Systemic insecticides timing application is not as critical, but should be applied as early as possible after sufficient foliage is present (10” stage). Growers might also consider burying the pupae by mounding soil up under the vines early in the season (late April). This form of cultural control might prevent adults from reaching the soil surface.

Vertebrate Pests

Birds: Birds are a major pest problem in grapes. Left unchecked, they can destroy enough of the crop to ruin the profitability of a vineyard. The loss of chemical deterrents has made bird control a more difficult task in recent times, but effective means are still available.

Netting is the most effective way to keep birds out of the vineyard. Although initial costs can be high, most netting will last for many years if cared for properly. Netting should be hung over some sort of support structure built around the vineyard. Usually posts are set nine feet above the ground around the perimeter of the vineyard, and wire is run from pole to pole to form a grid over the planting. The netting is hung over this grid when the fruit begins to turn color. Some temporary nine foot poles may be placed within the vineyard at intersections of the grid to keep the netting from drooping. Bury the edges of the netting or anchor it to the ground to keep birds from crawling underneath. Remove the netting when the harvest is complete, and store in a cool, dry place.

Visual scare devices have variable effectiveness on birds. Scarecrows, balloons, kites, or stuffed owls may work on certain bird species in certain areas, but none seem to have widespread dependability. When using scarecrows, “scare eye” balloons, stuffed owls, or snakes, put them in the vineyard only when the fruit begins to ripen, and move them regularly, at least once a day. Six scare-eye balloons per acre are recommended. Take them out of the field as soon as harvest is over. This will reduce the chance of birds becoming accustomed to the devices, and increase the longevity of their effectiveness. Kites and helium-filled balloons positioned high above the planting with a silhouette of a hawk hanging from them have provided good results in some areas.

Noise deterrents, such as propane cannons, alarms and recorded distress calls seem to have the least effect on birds in vineyards, but may greatly annoy neighbors. A combination of noise and visuals may be effective, however. Several operations have hired people to regularly drive motorcycles and/or ATVs through the vineyard when the fruit is ripe, and this seems to keep birds away quite well. Be sure to make drivers aware of where pickers are however, to avoid possible accidents.

Bird Shield™, a repellent formulated from methyl anthranilate, is currently being registered for use on blueberries, cherries, and grapes. Methyl anthranilate is commonly used as a grape flavoring in human food preparations. Bird avoidance is based on odor quality and irritation. To humans, this chemical has a grape-like or fruit odor and a slightly bitter, pungent taste. Unfortunately, efficacy data do not support recommending this material at this time.

For a complete discussion of bird control in fruit crops, see Bird Damage Prevention for Northern New England Fruit Growers by Dr. Alan Eaton of the University of New Hampshire.