Fruit Damaging Insects
Spotted Wing Drosophila (SWD) (Drosophila suzukii): SWD are invasive vinegar flies (fruit flies) that can attack unripen fruit. Female SWD cut into intact fruit with a serrated ovipositor to deposit eggs under the skin. This allows SWD larvae 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 be introduced, further affecting fruit quality. There is a much greater risk of fruit contamination at harvest from SWD compared with native species that lay eggs only in already-damaged and rotting fruit.
Management: Monitor blueberry fields with traps baited with apple cider vinegar plus ethanol alcohol (90% apple cider vinegar plus 10% ethanol) and/or fermenting yeast. Contact Cooperative Extension in your state for information on latest trapping techniques. Once adult SWD are trapped and blueberries begin to turn blue, apply insecticides weekly through harvest, rotating between insecticide classes. Choose insecticides based on efficacy and preharvest interval.
Insecticides may be made more effective by adding sugar to stimulate SWD feeding. Try adding 1-2 pounds of white sugar per 100 gallons of spray mixture.
Winter Moth (Operophtera brumata): This is a new and important pest of blueberries and other deciduous plants, especially in Southeastern New England. They can severely defoliate bushes. Moths emerge from the soil in late November and may be active into January. Male moths are light brown to tan in color and attracted to lights at night. Females are gray, almost wingless and cannot fly. Females can be found at the base of trees or on tree trunks. After mating, females deposit tiny eggs in bark crevices or among lichens which overwinter. Eggs begin hatching in late March or early April after the first warm days of spring, generally around 20 Growing Degree Days (GDD) (base 50˚F) or about 200 GDD (base 40˚F). Egg hatch coincides with bud break of McIntosh apple trees. After hatching, larvae wriggle into swelling buds of blueberries and many tree and begin feeding. Caterpillars continue feeding on leaves and flowers until late May when they drop to the ground to pupate. Destruction of flower buds can greatly reduce yield.
Winter moth larvae are pale green caterpillars with white longitudinal stripes running down both sides of the body. They are “loopers” or “inchworms” and have just 2 pairs of prolegs. Mature caterpillars are approximately one inch long.
Management: A dormant oil spray to trunks and branches of bushes may be helpful killing overwintering eggs before hatching. However, some eggs are under bark flaps and loose lichen and may be protected from oil sprays. Caterpillars may also invade blueberries by ballooning into plantings. Bacillus thuringiensis (B.t. kurstaki), manages winter moth caterpillars well once caterpillars are feeding on exposed foliage. B.t. and other insecticides are not effective when caterpillars are feeding inside closed buds. Spinosad is another biorational compound that works well against winter moth caterpillars. Finally, tebufenozide (e.g. Confirm) is an insect growth regulator (IGR) that works well on most lepidopteran caterpillars.
Blueberry Maggot (Rhagoletis mendax): The adult is a black fly about 1/5” long with a pattern of dark and clear bands on its wings. The maggots are white, legless, and about 1/4” long when full grown. Flies alight on fruit to lay eggs under the fruit skin just as fruit begins to turn blue. Maggots are later found in ripening and harvested fruit, making fruit unmarketable since berries become soft and mushy. Undetected infested berries contaminate pack-out.
Management: Red sticky spheres or yellow sticky rectangle traps (available from suppliers listed in appendix) can be used to monitor blueberry maggot populations in plantings. In large bushes, sticky traps should be hung in upper half of the canopy, suspended from wires and about 1-1/2 feet from outer foliage. All fruit and foliage within 8 inches of trap should be cleared away, and all traps positioned so that there is as much foliage and fruit surrounding them as possible. In small plantings, it may be possible to trap out this insect with a sufficient number of traps. Consult with your state’s regional fruit specialist for further information. Spray recommendations are found in the blueberry pest management schedule.
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 are 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 deposited 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 fruit with piercing/sucking mouthparts. Fruit tissue dies at the point of entry and just below into the flesh, and the rest of the fruit grows around it. This leaves sunken areas on the skin and browning, dead tissue in the flesh.
BMSB has become a serious insect pest in mid-Atlantic states, southern New York, Connecticut, and possibly other New England states. It is unknown at this time whether there is one or two generations per year in New England.
Management: BMSB cannot be controlled with many common fruit insecticides, including Imidan and Sevin. Spray recommendations are found in the blueberry pest management schedule.
Plum Curculio (Conotrachelus nenuphar): This dark brown snout beetle is about 1/4” long with 4 humps on its wing covers. It feeds on developing flower buds and developing berries. Females lay eggs on the fruit, and after hatching, light colored larvae develop inside the fruit (one larva per fruit). Larval feeding causes fruit to ripen prematurely and drop off bushes.
Management: Plum curculio are more abundant where blueberries are located near tree fruit. If possible, plant blueberries away from tree fruit. Spray applications made at petal fall to manage cranberry or cherry fruitworm also likely manage plum curculio.
Cranberry Fruitworm (Acrobasis vaccinii): Cranberry fruitworm larva (caterpillar) is green with some brownish-red coloration on its top surface, measuring 1/2” at maturity. It is found within developing and ripening berries. Feeding reduces yield and spoils marketability of berries. Eggs are laid in the calyx cup (blossom end) of unripe fruit. Hatched larvae move to the stem end of fruit, enter, and feed inside berries. Larvae consume 3-6 berries, filling berry skins with brown frass and tying berries together with silk.
Management: When damage is severe, treat the following year with insecticide. See pest management schedule for recommended materials. In small plantings, cranberry fruitworms may be managed by picking off infested berries, which are easily detected due to webbing and early ripening. Eliminating weeds around plants reduces overwintering protection for cocoons.
Cherry Fruitworm (Grapholita packardi): At maturity, cherry fruitworm larvae are orange-red and about 1/4-1/2” long and found within developing and ripening berries. Feeding reduces yield and spoils marketability of berries. Soon after petal fall, hatching larvae bore into the calyx cup (blossom end) of berries, feed until about half-grown, and then move to a second fruit. (This is distinct from the cranberry fruitworm described above.) The two infested berries are usually joined by silk.
Management: When damage is severe, treat the following year with insecticide. See pest management schedule for recommended materials.
Leaf/Shoot Damaging Insects
Gypsy Moth (Lymantria dispar dispar): Young gypsy moth larvae (caterpillars) are hairy, dark brown to black in color and older caterpillars are marked with red and blue spots. They range in size, from 1/4 to 2” in length, depending on age. In outbreak years, larvae feed on leaves and buds, causing complete or partial defoliation and fruit loss.
Management: Remove egg masses present in plantings by early April. Small caterpillars can blow in from surrounding, infested trees in early May. Bt insecticides effectively manage small, young caterpillars, but other insecticides are needed to manage large larvae. See pest management section for insecticide recommendations.
Blueberry Blossom Weevil; Cranberry Weevil (Anthonomus musculus): This is a dark reddish brown snout beetle, 1/8” long, with a curved snout. It emerges in spring, feeds and lays eggs in expanding flower and leaf buds. Weevils hide between clustered buds, and small infestations may be difficult to find. Damage results when punctured flowers do not open. Damaged leaf buds produce an abnormal cluster of dwarfed leaves. Adults of the second generation sometimes feed on blueberry leaves.
Management: No insecticides are labeled for this pest. Disking between rows and raking/hoeing under plants is helpful. Eradication of wild blueberries or other ericaceous plants in the vicinity of the blueberry planting may be beneficial.
Scale Insects; Putnum Scale and Lecanium Scale (Aspidiotus ancylus and Lecanium nigrofasciatum): These insects appear mound-shaped, of varied colors, and usually measuring 1/8” or less in length. They are found on rough, loose bark of older stems and sometimes on fruit. Infestations can result in reduced vigor and yield of bushes by feeding on plant sap. Fruit lecanium scale eggs hatch in early July (late June in southernmost New England) and first generation putnam scale crawlers emerge in early June.
Management: Good pruning is the first step in controlling scale insects. Prune out weakened canes. During dormancy, apply superior-type oil of 60- or 70-second viscosity at 3 gallons per 100 gallons of water. To avoid injury, apply when there is no danger of freezing temperatures for at least 24 hours after treatment. See Insecticide Efficacy and Pest Management Tables in this chapter for other recommended materials and timing.
Blueberry Tip Borer (Hendecaneura shawiana): In June, before new growth has begun to harden, some blueberry shoots may begin to wilt, arch over, and become discolored, the leaves turning yellowish with red veins and stems turning purplish. This injury, which may be mistaken for primary mummyberry infection, is caused by blueberry tip borer. Newly hatched caterpillar, tiny and pink, enters soft stem and bores channels that may extend for 8 or 10” by autumn and result in the destruction of the stem’s fruit-production potential the following year.
Management: Prune out damaged tips when found and burn infected canes. A standard spray program used for other insect pests normally keeps this pest under control.
Blueberry Bud Mite (Acalitus vaccinii): Blueberry bud mites are whitish in color and tiny. Unlike other mites, they are elongate and conical, with 4 legs bunched near the head at the broad end of the mite. Heavily infested buds have a definite reddish coloration and characteristic rough bumps on outer bud scales. Eggs, immatures, and adult mites are present throughout the year, generally confined to buds and blossoms. During fall and winter, many mites may be found between scales of a single fruit bud.
Bud mites feed on the surface of bud tissues and bud scales. Injured buds desiccate and usually produce distorted flowers. These flowers may fail to set fruit, or develop into fruit with rough skins. The potential for damage differs with variety.
Management: Plants should be inspected for bud mites in September, before new buds are well formed. Look for them under bud scales and between bud parts. Economic threshold levels have not been determined for bud mites. Thorough pruning of infested canes provides good control of bud mites. Limited chemical control measures are available.
Blueberry Stem Gall Wasp (Hemadas nubilipennis): The adult blueberry stem gall wasp is a small (less than 1/8”) shiny black insect with delicate wings. It lays eggs in succulent shoots. Several grub-like larvae develop together inside the shoot, stimulating the shoot to grow abnormally and resulting in a pithy, kidney-shaped gall 3/4 to 1-1/4” long. Pupation occurs within larval chambers and new adults bore an exit hole through the gall. Early in the season galls are greenish and spongy to the touch. By fall the galls turn brownish-red and become hard. Shoot growth is reduced and the shoot may be diverted at severe angles.
Blueberry stem gall wasp can cause severe reduction in shoot growth and stem vigor. Hundreds of galls can develop on a single bush, reducing fruit production. Susceptibility to galls may depend on variety. This insect is rarely encountered in fields managed with standard chemical pesticide programs, but it can be a major pest of organically managed fields.
Management: Chemical treatments directed toward other pests are generally sufficient to keep stem gall in check. Removal and destruction of gall during normal pruning operations will also help manage this pest.
White Grubs - Japanese Beetle (Popillia japonica), Rose Chafer (Macrodactylus subspinosus), Asiatic Garden Beetle (Maladera castanea), and others: White grubs are the larvae of a variety of beetle species some of which are listed above. White grub larvae are generally white or cream colored with brown heads and legs, and hold their bodies in a distinct hooked or C-shape. Stretched out, larger species may be over one inch in length. Many white grub species can be identified by distinctive patterns of stiff hairs located at the underside of abdomen tip. Most species overwinter as grubs deep in the soil and pupate in late spring before emerging as adult beetles. Some species feed on roots of plants for more than one year before completing development. Time of pupation and adult emergence varies with species.
Adults of white grubs are known generically as May Beetles, June bugs, chafers, or scarab beetles. The adults of some species feed on foliage, flowers and fruits of many plants. Japanese beetle and rose chafer adults can be significant pests of blueberry during harvest when they contaminate berries.
Recently white grubs have become serious pests in some fields, with populations as high as 30 grubs per bush. Grubs consume feeder roots and may also girdle or clip off larger roots. Infested plants may not show any outward signs of injury until a period of drought stress, when the reduced root system cannot provide enough water to the plant. Damaged bushes show low vigor and reduced production. Adults, especially Japanese beetle and rose chafer, sometimes become serious pests by consuming leaves and scarring berries.
Management: Unfortunately, sampling for white grubs damages roots of blueberry bushes. Growers should check new sites for white grubs before establishing a field, and take actions against grubs before planting. Admire Pro can be applied to soil to control white grubs. When applied correctly, it suppresses Asiatic garden beetle larvae and is effective against all other species of white grubs. There is great interest in the use of pathogenic nematodes as biological control agents for grubs. Adults are generally easy to control with foliar sprays, but timing is difficult since these are highly mobile insects that may suddenly appear in the field. Surround is a kaolin clay-based product that can deter adults from feeding on foliage. It may be of interest to organic growers, though removing Surround from fruit would be difficult.
Yellow-necked Caterpillar (Dantana ministra): These hairy yellow caterpillars are usually found in large groups in mid- or late summer. If unnoticed, they can entirely strip foliage from a bush.
Management: Caterpillar strains of Bacillus thuringiensis (Bt) products are effective in managing larvae, especially when they are small. Chemical insecticides are also effective. Spraying the entire planting is not required.
Sharp-nosed leafhopper (Scaphytopius acutus): SNLH feeds and reproduce on blueberry, huckleberry, cranberry, and other related plants. SNLH feeding causes little direct damage but it transmits the phytoplasma that causes stunt disease in blueberries. They are small brown insects with a pointed head. SNLH picks up the disease while feeding on infested bushes and carries it to other plants in subsequent feedings. Usually only adults carry the disease from plant to plant, since nymphs are wingless and can’t fly. Adults are abundant in the woods and may move to commercial blueberry fields in the spring. Eggs overwinter inside fallen leaves and hatch in mid-May. Nymphs from the first generation reach adult stage in mid-June, while nymphs from the second generation reach adulthood in early August. Adults move back to the woods in the fall.
Management: First generation SNLH is often controlled with sprays targeted for plum curculio, aphids, and cranberry fruitworm. Treatment decisions for the 2nd generation should be based on individual population levels, as well as any history of stunt disease on your farm. Because adults migrate from woods, monitoring should concentrate on field perimeter. Insecticides are usually applied just prior to peak flight, generally late August to early September. It is also important to remove all plants that show symptoms of stunt disease. Removal of bushes should be done after insecticide treatment to avoid movement of leafhoppers from infested to healthy plants.
Blueberry aphid (Illinoia pepperi) is the vector of blueberry shoestring virus which can cause bush decline and significant yield reductions. It is also a potential vector of blueberry scorch virus. Because of the ability of aphids to serve as vectors of plant disease, they should be controlled to minimize virus spread in infected fields and in susceptible fields near to virus-infected fields.
Management: Blueberry aphids are most often found on the undersides of young leaves at the base of plants. Insecticides can be applied in June as aphid populations start to increase. Spray should be directed at base of plants and good coverage is essential for effective aphid control. This will be more challenging in weedy fields.
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*Restricted use material; pesticide applicators license required. OMRI certified for organic production