Pests
Symptoms Birds eating your berries, often clearing the bush right as the fruit ripens.Ripening and ripe berries stripped from the bush, often the entire crop in a few days as fruit colors up. Pecked and partly eaten berries left behind. Cause Birds love ripe blueberries and are the biggest blueberry pest there is.Birds (robins, cedar waxwings, and others) are drawn to ripening blueberries and are widely rated the number-one blueberry pest by growers. Organic treatment Cover the bush with bird netting before the berries turn blue, and tuck it in at the bottom so birds cannot sneak in. Netting works far better than scare devices.Netting is the most effective control. Drape bird netting (about 1/2 to 3/4 inch mesh) over the bush or a frame before berries begin to color, and secure it at the base so birds cannot get underneath. Prevention Put netting up every year before the fruit ripens. Shiny tape and fake owls stop working once birds get used to them, so netting is the dependable fix.Install netting pre-ripening every season. Scare tactics (reflective tape, decoys) help only briefly as birds habituate; physical exclusion is the reliable answer.
Symptoms Tiny maggots inside ripe berries, with fruit going soft and mushy. The adult is a small fly with a spot on the wing.Small white maggots inside ripe berries; fruit softens, collapses, and leaks when squeezed. A tiny vinegar-fly-like adult, the male with a dark spot near each wingtip. Damage often unseen until fruit is opened. Cause A small invasive fruit fly that lays eggs in good, ripe berries (not just rotten ones), and the maggots feed inside.Spotted-wing drosophila (Drosophila suzukii), an invasive vinegar fly whose females cut into healthy ripe fruit to lay eggs, unlike common fruit flies that only use rotting fruit. Organic treatment Pick ripe berries often and clean up any fallen or overripe ones (seal them in a bag, do not compost). Very fine netting keeps the flies off. You can monitor with a cup of apple cider vinegar as a trap.Harvest frequently and completely (every one to three days) so ripe fruit is not left on the bush, and remove and destroy any fallen or overripe berries (bag them, do not compost). Fine exclusion netting (less than 1 mm mesh) over fruiting plants reduces egg-laying. Monitor with apple-cider-vinegar traps. Prevention Grow early varieties when you can, keep the ground clear of fallen berries, and pick often. Fine netting before ripening is the best prevention.Choose early-ripening cultivars to dodge peak fly pressure, keep the planting clean of dropped fruit, and harvest on a tight schedule. Combine monitoring with exclusion before berries ripen.
Symptoms Small white maggots in ripening berries, from a little banded-wing fly that shows up in summer.White, legless maggots inside ripening fruit; infested berries soften. The adult is a small fly, roughly 3/16 inch, with dark bands across the wings, active from June or July through August. Cause A native fruit fly that lays eggs in nearly ripe berries, and the maggots feed inside the fruit.Blueberry maggot (Rhagoletis mendax), a native fruit fly. The female deposits one egg just beneath the skin of each almost-ripe berry, and the larva develops inside the fruit before dropping to the soil to pupate. Organic treatment Pick often and clean up dropped or buggy berries (do not compost them). Yellow sticky traps put up before the berries ripen help you spot the flies.Harvest promptly and frequently, and remove infested and dropped fruit so larvae cannot complete their cycle in the soil. Do not compost infested berries, since pupae survive composting. Monitor with baited yellow sticky traps before ripening. Prevention Watch for the fly with sticky traps before harvest, keep fallen fruit picked up, and harvest often. Netting keeps the flies off too.Monitor with yellow sticky traps starting a few weeks before ripening, keep fallen fruit cleaned up, and harvest on a tight schedule. Netting also excludes the adult fly.
Symptoms Tiny soft bugs on new shoots and the undersides of leaves, sometimes with sticky residue.Small soft-bodied insects clustered on tender new growth and leaf undersides, sometimes distorting new shoots and leaving sticky honeydew. Mainly a concern as virus vectors rather than for direct feeding damage. Cause Small sap-sucking insects whose bigger risk is spreading plant viruses.Several aphid species feed on blueberry sap; their main importance is the potential to transmit blueberry viruses. Organic treatment Spray them off with water, let ladybugs help, or use insecticidal soap if there are a lot. Do not over-fertilize, which makes the soft new growth they love.Knock light infestations off with a strong spray of water, encourage natural predators like ladybugs, and use insecticidal soap if needed. Avoid over-fertilizing with nitrogen, which fuels soft growth aphids prefer. Prevention Do not over-feed, encourage helpful bugs, and check new growth in spring.Keep plants healthy without excess nitrogen, support beneficial insects, and inspect new growth in spring. Manage nearby weeds that host aphids.
Symptoms Little hard bumps stuck to the stems, sometimes with black sooty mold nearby.Small, immobile bumps on stems and older wood, sometimes with associated sooty mold on honeydew. Heavy infestations can weaken canes and reduce vigor. Cause Sap-sucking insects that stick to the branches and can weaken the bush.Several scale insects attach to blueberry wood and feed on sap, secreting honeydew that supports sooty mold. Organic treatment Cut out badly infested branches in winter, and spray dormant oil to smother them. Helpful insects keep them in check too.Prune out and destroy heavily infested wood during dormant pruning, and apply dormant horticultural oil to smother overwintering scale. Encourage natural enemies. Prevention Prune for good airflow and check older branches in winter.Keep bushes vigorous and well pruned for good air movement and light, and inspect older canes during dormant pruning.
Diseases
Symptoms In spring, new shoots and flowers suddenly wilt and turn brown as if frost-hit. Later, berries shrivel into hard tan mummies and fall off.In spring, newly emerging shoots, leaves, and flower clusters suddenly wilt, brown, and die as if frosted, later dusted with gray spores. Infected berries look normal at first, then turn tan or reddish, shrivel, and drop as hard gray mummies. Cause A fungus that lives in old shriveled berries on the ground over winter, then infects new shoots and flowers in spring.The fungus Monilinia vaccinii-corymbosi, which overwinters in mummified berries on the ground and infects in two phases: emerging shoots first, then flowers, which spread it to the fruit. Organic treatment Clean up and throw away the old shriveled berries under the bush, and rake or add fresh mulch in late winter to bury them before they release spores. Choose resistant varieties.Sanitation is the core organic control: rake up and destroy fallen mummies, and shallowly cultivate or mulch under bushes in late winter to bury overwintering mummies before their spore cups form. Remove highly susceptible cultivars from mixed plantings. Prevention Pick resistant varieties, keep fallen berries cleaned up, mulch under the bush, and prune for airflow. It is worst in cool, rainy springs.Choose resistant cultivars, keep the ground under bushes clean of mummies, mulch to bury spore sources, and improve air movement. Cool, wet spring weather worsens it.
Symptoms Leaves yellow or redden, the bush stunts and dies back, and the roots turn brown and rotten. It strikes plants in soggy soil.Aboveground: yellowing or reddening leaves, stunted growth, branch dieback, defoliation, and eventual plant death. Belowground: roots turn brown to black and rot. Most common in heavy or poorly drained soils. Cause A soil disease that rots the roots when the soil stays too wet.Soilborne Phytophthora water molds that attack roots in wet, poorly drained soil. Southern highbush is more susceptible than rabbiteye. Organic treatment There is no fixing rotted roots, so it is all about prevention: plant in raised beds with good drainage, and replace dead plants with healthy ones in a drier spot.There is no organic cure once roots are rotted; management is preventive. Improve drainage, plant on raised beds or mounds, and remove and replace dead plants with clean nursery stock on a better-drained site. Prevention Plant in raised beds with soil that drains well, never let the bush sit in soggy soil, and buy healthy plants. Good drainage prevents it.Plant only in well-drained, acidic soil; use raised beds in heavy ground; avoid overwatering and waterlogging; and start with disease-free nursery plants. Good siting is the whole game.
Symptoms Flowers turning brown and getting a fuzzy gray mold in cool, damp weather.Blighted, browned flowers and blossom clusters, sometimes covered with fuzzy gray mold in cool, wet conditions. Can lead to fruit rot. Frost-injured blossoms are especially vulnerable. Cause A gray-mold fungus that attacks flowers in cool, wet, crowded conditions.The fungus Botrytis cinerea, favored by cool, wet, humid weather during bloom and by frost-damaged or dense, poorly ventilated tissue. Organic treatment Prune to open up the bush so air flows, water at the base rather than over the flowers, and remove moldy flower clusters.Improve air circulation through pruning, avoid overhead watering that wets blossoms, and remove blighted clusters. Good spacing and canopy openness reduce the humidity it needs. Prevention Keep the bush open and airy, water low, and protect flowers from frost. Dry flowers do not get moldy.Prune for an open canopy, water at the base, avoid excess nitrogen, and protect bloom from frost. Dry, well-ventilated flowers rarely blight.
Symptoms Ripe berries developing soft sunken spots and rotting, sometimes with orange ooze, on the bush or soon after picking.Ripening and ripe berries develop soft, sunken spots, often with salmon to orange spore masses; fruit rots on the bush or quickly after picking. Lesions can also appear on leaves and stems. Cause A fungus that infects in wet weather and rots the berries as they ripen or in storage.The fungus Colletotrichum (anthracnose), which infects during bloom and wet weather and shows up as fruit rot at ripening; it is also a common post-harvest rot. Organic treatment Open up the bush for airflow, water at the base, pick ripe berries promptly, and refrigerate them fast. Throw away rotted berries.Prune for air movement, avoid overhead irrigation, harvest promptly, and cool fruit quickly after picking to slow the rot. Remove and destroy rotted fruit. Prevention Keep the bush airy, water low, pick on time, and chill berries right away. Some varieties resist it better.Improve canopy ventilation, manage moisture during bloom and ripening, harvest on time, and cool fruit immediately. Some cultivars are more resistant.
Symptoms Branches and twigs dying back, with reddish-brown patches spreading down the wood.Branches, twigs, and canes die back with reddish-brown lesions that spread from smaller wood toward larger branches; affected canes wilt and die. Can kill young plants outright. Cause Fungi that get into the branches through wounds or winter-damaged wood and cause dieback.Fungal canker pathogens (including Botryosphaeria stem blight and Phomopsis twig blight) that enter through wounds and stressed or winter-injured wood. Organic treatment Cut out dying branches well below the damage, clean your pruners between cuts, and keep the bush healthy so it resists infection.Prune out affected wood well below the lesion into healthy tissue, disinfecting tools between cuts, and remove debris. Keep plants vigorous and unstressed; avoid winter injury. Prevention Grow healthy, well-adapted plants, prune out diseased wood cleanly, and avoid stressing the bush. Some varieties resist it better.Plant adapted, vigorous cultivars; avoid drought and winter stress; prune cleanly and remove diseased wood; and keep good air movement. Resistance is variety-led.
