Pests
Symptoms Round holes chewed in the leaves, and worse, chewing on the pods themselves and even pods clipped off at the stem late in the season. The adult is a small reddish or yellowish beetle with a little black triangle behind its head and rows of black spots on its back.Round to irregular holes chewed through the leaves, and on the pods the more damaging sign: chewing on the pod wall and, late in the season, clipping at the base of the pod that drops it entirely. The adult is a small reddish to yellowish beetle with a black triangle behind the head and usually a row of black spots along each wing cover. Cause The bean leaf beetle, the main leaf-eating beetle of soybeans. The adults move into young plants in spring, and a summer generation feeds on the pods, which is the worst damage. It can also spread a virus from plant to plant.The bean leaf beetle (Cerotoma trifurcata), the most important leaf-feeding beetle of soybeans. Overwintered adults move into seedlings in spring, and a later summer generation feeds on the pods, which is the costly stage. It also transmits bean pod mottle virus. Organic treatment Edamame can lose a fair amount of leaf early without losing beans, so light leaf damage needs nothing. Pick beetles off in a small patch, and focus on protecting the pods later in the season, when the beetles do the real harm. A light row cover keeps them off, and an organic spray such as spinosad helps if they get bad.Edamame tolerates a lot of early leaf feeding without losing yield, so light damage on the foliage needs nothing. Handpick adults in a small patch, and protect the pods later in the season, when pod feeding and clipping matter; a floating row cover keeps beetles off, and an organic option such as spinosad or pyrethrin is labeled where pressure is heavy. Prevention Because the pod damage is the worst part, planting early so the pods finish before the summer beetles build up helps. Clear away the old plants after harvest and move your edamame each year, and cover young seedlings with a row cover if this beetle is a problem where you are.Since pod feeding is the costly damage, an early sowing that fills pods before the summer beetle generation peaks helps. Clear crop debris after harvest and rotate edamame away from last year's bed to remove overwintering shelter; a row cover protects emerging seedlings where the beetle is a known problem.
Symptoms Pods that look fine on the outside but hold flat, shrunken, or stained beans inside, because the bugs poke through the pod and feed on the seeds. Stink bugs are shield-shaped insects about half an inch long, green or brown.Pods that look intact from outside but hold flat, shriveled, or discolored beans, because the bugs pierce the pod wall and feed on the developing seeds. Green and brown stink bugs are shield-shaped insects about half an inch long; their feeding scars the seed and can stop it filling. Cause Several kinds of stink bugs, including the green, brown, and brown marmorated stink bugs. They matter because they feed straight on the beans inside the pods while the pods are filling, which is the part you eat.The stink bug complex (green stink bug, brown stink bug, and the invasive brown marmorated stink bug). They are among the most damaging soybean pests because they feed directly on the seed during pod fill, exactly the part of edamame you eat. Organic treatment Pick the shield-shaped bugs and their barrel-shaped egg clusters off by hand, checking while the pods fill. Keep weeds down around the bed, since the bugs come in from weedy edges, and use an organic spray only if they are really feeding on the pods.Handpick the shield-shaped adults and the barrel-shaped egg clusters in a home patch, checking through pod fill. Keep weeds down around the bed, since stink bugs move in from weedy edges, and treat with an organic option such as spinosad or pyrethrin only where feeding on the pods is heavy. Prevention Check the pods from the time they set through filling, which is when stink bugs do harm. Clear weedy edges that shelter them before the season, move your edamame each year, and clean up old plants after harvest. An early variety can finish before the bugs peak in late summer.Watch the pods closely from pod set through fill, the window stink bugs damage. Mow or clear weedy borders that harbor them ahead of the season, rotate the bed, and clean up debris after harvest. An early-maturing crop can finish before peak late-summer pressure.
Symptoms Clusters of tiny, soft, pale-yellow insects on the growing tips and undersides of the upper leaves, sometimes with ants around them. Heavy feeding curls and yellows the leaves and leaves a sticky residue, and the aphids can spread viruses.Colonies of small, soft, pale-yellow aphids on the growing tips, undersides of upper leaves, and stems, often tended by ants. Heavy feeding puckers and yellows the leaves, stunts the plant, and leaves a sticky honeydew that blackens with sooty mold; the aphids also transmit several plant viruses. Cause The soybean aphid, an invasive aphid that feeds only on soybeans and can multiply fast in midsummer. Mild weather lets it build up quickly, and ladybugs and other helpers usually bring it down.The soybean aphid (Aphis glycines), an invasive aphid specific to soybeans that can build explosively in midsummer. Cool to warm, calm weather favors rapid buildup; ladybugs and other natural enemies usually catch up. Organic treatment Spray the colonies off with a strong jet of water or use insecticidal soap, starting while there are only a few. Ladybugs and other helpful insects usually finish the job, so avoid sprays that kill them too. Deal with aphids early since they can spread viruses.Knock colonies off with a strong spray of water or treat with insecticidal soap, beginning while numbers are low. Ladybugs, lacewings, and parasitic wasps usually control soybean aphid in a garden, so avoid broad sprays that kill those helpers. Act early, since the aphids also move viruses. Prevention Do not overfeed with fertilizer, since the soft new growth is what aphids like, and keep weeds down nearby. Reflective mulch confuses them and cuts the viruses they spread, and helpful insects do most of the work in a home garden.Avoid overfeeding with nitrogen, which produces the soft growth aphids favor, and keep nearby weeds and buckthorn (the aphid's overwintering host) in check. Reflective mulch disorients them and reduces virus spread, and natural enemies do most of the work in a home garden.
Symptoms Leaves chewed down to a lacy skeleton of veins, the classic Japanese beetle damage, as the shiny green-and-copper beetles feed in groups on top of the plants in midsummer. They can strip a lot of leaf, but edamame handles a fair amount of leaf loss.Leaves skeletonized to a lacy network of veins, the classic Japanese beetle signature, as the metallic green-and-copper adults feed in groups on the upper canopy in midsummer. Heavy feeding can strip the foliage, though edamame tolerates a good deal of leaf loss before yield suffers. Cause The Japanese beetle, a shiny green beetle with copper wings whose grubs live in lawns and whose adults feed on many plants, including soybeans, in midsummer.The Japanese beetle (Popillia japonica), a metallic green beetle with coppery wing covers whose grubs develop in lawns and whose adults feed on many garden plants, soybeans included, through midsummer. Organic treatment Pick the beetles off in the early morning when they are slow, dropping them into soapy water; this works well in a garden. Skip the beetle traps, which often attract more beetles than they catch. Since edamame handles a lot of leaf loss, light damage needs no spray.Handpick the beetles in the early morning when they are sluggish, knocking them into soapy water; this is effective in a home patch and avoids the traps, which draw in more beetles than they catch. Because edamame tolerates real defoliation, light to moderate feeding on the leaves needs no spray. Prevention Watch through midsummer, when the adults feed, and cover plants with a row cover during a heavy beetle flight if needed. Keeping the lawn a bit drier in midsummer means fewer grubs, and light leaf damage is better tolerated than sprayed.Watch through midsummer, the adult-feeding window, and protect plants with a floating row cover during a heavy flight if needed. Healthy lawns kept on the dry side in midsummer support fewer grubs; tolerate light leaf feeding rather than spraying.
Symptoms Fine whitish or yellow speckling on the leaves, turning to a dried, bronzed look, with fine webbing on the undersides. The mites are tiny specks, easiest to see by tapping a leaf over white paper. They explode in hot, dry weather.Fine whitish or yellow stippling on the leaves that progresses to a bronzed, dried-out look, with fine silken webbing on the undersides; the mites are minute specks, easiest to confirm by tapping a leaf over white paper. They build explosively in hot, dry weather. Cause Two-spotted spider mites, tiny relatives of spiders that pierce the leaf and suck out the contents. Hot, dry, dusty weather and dried-out plants let them build up fast, so they flare in dry midsummer.Two-spotted spider mites (Tetranychus urticae), tiny relatives of spiders that pierce leaf cells and suck the contents. Hot, dry, dusty conditions and drought-stressed plants favor rapid buildup, so they flare in dry midsummer spells. Organic treatment Spray the undersides of the leaves with a strong jet of water to knock off the mites and webbing, and use insecticidal soap before they get thick. Keeping the plants well watered and unstressed slows them down, and helpful bugs pitch in.Hose the undersides of leaves with a strong spray of water to dislodge mites and webbing, and treat with insecticidal soap or horticultural oil before numbers climb. Keeping plants well watered and unstressed slows buildup, and natural predators help. Prevention Keep the soil evenly moist, because dried-out plants are much more likely to get mites, and keep dust down. Check the undersides of the leaves during hot, dry weather so you catch them early.Maintain even soil moisture, since drought-stressed plants are far more mite-prone, and keep dust down around the bed. Watch the undersides of leaves through hot, dry spells so you catch the buildup early.
Diseases
Symptoms Stems with a white, cottony mold at the joints, sometimes with hard black lumps in them; the stem above bleaches, wilts, and dies. It shows up in cool, wet weather where the plants are crowded and the air does not move.Water-soaked lesions on the stems at the nodes that turn into a white, cottony fungal growth, often with hard black resting bodies (sclerotia) inside or on the stems; affected stems bleach, wilt, and die above the lesion. It develops in cool, wet weather in dense, lush canopies with poor airflow. Cause A fungus, the same white mold that hits beans. Hard black survival bodies live for years in the soil and sprout in cool, damp weather to infect the plants, especially where crowded, overfed growth keeps the leaves humid.The fungus Sclerotinia sclerotiorum, the same white mold that hits beans. Its hard black sclerotia survive years in the soil and germinate in cool, moist conditions to infect flowering plants, especially where dense, overfed growth keeps the canopy humid. Organic treatment There is no home spray that cures it; you manage it by how you grow. Pull and throw away (do not compost) infected plants, since the black lumps survive, and space the plants out so the leaves dry faster.There is no home-garden cure once plants are infected; management is cultural. Remove and destroy infected plants (do not compost them, since the sclerotia survive), and open up spacing and airflow to dry the canopy. Prevention Give plants room so air moves through them, and go easy on fertilizer, since heavy growth feeds the mold. Move edamame away from beans on a long rotation, water at the base instead of overhead, and avoid spots where white mold has been bad.Space plants and rows for good airflow rather than crowding, and go easy on nitrogen, since excess feeding drives the dense growth the mold needs. Rotate away from beans and other susceptible crops on a long cycle, avoid overhead watering, and do not plant where white mold has been severe.
Symptoms Small angular spots on the leaves that turn brown to black with a yellowish ring, often falling out to leave the leaves looking torn. It likes cool, wet weather and spreads in blowing rain. It is the most common leaf disease of soybeans.Small, angular, water-soaked spots on the leaves that turn brown to black with a yellow-green halo, the spots often dropping out to leave a ragged, tattered look; it favors cool, wet weather and spreads in wind-driven rain. The most common foliar disease of soybeans. Cause A bacterium that survives the winter on old plant debris and seed. Splashing rain and touching wet plants carry it from leaf to leaf, and cool, wet weather is when it strikes.The bacterium Pseudomonas savastanoi pv. glycinea. It overwinters on infected residue and seed, and splashing rain and handling wet plants move it from leaf to leaf; cool, wet conditions favor infection. Organic treatment There is no cure once plants are infected, but it rarely costs much in a garden. Water at the base, not overhead, and stay out of the patch when the leaves are wet, since that spreads the bacteria.There is no cure once plants are infected; the disease rarely causes real yield loss in a garden. Avoid overhead watering and do not handle plants when the foliage is wet, which moves the bacteria from plant to plant. Prevention Plant clean seed and do not save seed from infected plants, since the disease travels on seed. Move your edamame each year, clear away old plants after harvest, give the plants room, and keep out of the patch when the leaves are wet.Plant clean seed and do not save seed from an infected crop, since the disease is seedborne. Rotate away from soybeans and beans, clear residue after harvest, give plants room for airflow, and keep out of the bed when the foliage is wet.
Symptoms Pale green to yellow blotches on top of the leaves with a grayish, fuzzy growth underneath in humid weather; the spots grow and turn brown. It is common but usually mild, and infected seed can have a white coating.Pale green to yellow spots on the upper leaf surface with a matching grayish, downy fungal growth on the underside in humid weather; spots enlarge and brown. It is common but usually minor, and seed from infected plants can carry a white crust. Cause A fungus-like organism that likes warm, humid weather and wet leaves. It survives on old plant debris and seed and spreads in damp, humid spells.The fungus-like organism Peronospora manshurica, favored by warm, humid weather and frequent leaf wetness. It survives on residue and seed and spreads on wind and splashing in humid spells. Organic treatment Downy mildew rarely needs treatment in a garden; the plants usually grow through it. Give the plants room and avoid wetting the leaves to slow it, and pull badly spotted leaves if you like.Downy mildew seldom needs treatment in a home garden; edamame outgrows light infection. Improve airflow and avoid wetting the foliage to slow it, and remove badly spotted leaves where practical. Prevention Give plants room so the leaves dry, water at the base, and move your edamame each year. Clear away old plants after harvest and use clean seed, since it carries over on debris and seed.Space plants for airflow, water at the soil rather than overhead, and rotate away from soybeans. Clean up residue after harvest and use clean seed, since the organism carries over on debris and seed.
Symptoms Patches of stunted, yellow, slow plants, usually in spots rather than all over, with very few of the normal root nodules. The clue is tiny lemon-shaped white or yellow specks (cysts) on the roots in summer.Patches of stunted, yellowed, slow-growing plants, often in spots rather than uniformly, with few nodules and tiny lemon-shaped white to yellow females (cysts) just visible on the roots in summer. Above-ground symptoms are easy to miss, but the cysts on the roots are the giveaway. Cause The soybean cyst nematode, a microscopic worm that is the most damaging soybean pest in much of the country. Its egg-filled cysts survive in the soil for years and build up where soybeans grow in the same spot again and again.The soybean cyst nematode (Heterodera glycines), a microscopic roundworm that is the most damaging soybean pest in much of the country. Its cysts hold eggs that survive in the soil for years, and they build up where soybeans are grown repeatedly. Organic treatment There is no home treatment once it is established; you manage it by prevention. If plants are stunted in patches, check the roots for the tiny cysts in summer, and avoid carrying soil from that bed to clean ground on tools or shoes.There is no rescue treatment in a home garden; management is preventive. Where plants are stunted in patches, check the roots for cysts in summer and avoid moving soil from that bed to clean ground on tools or shoes. Prevention Rotate edamame with crops other than soybeans and dry beans on a long cycle, which is the main control, and never grow soybeans in the same spot every year. Where it is a known problem, plant resistant varieties and keep weeds down.Rotate edamame with non-host crops (anything but soybeans and dry beans) on a long cycle, the main control, and do not grow soybeans in the same bed year after year. Where the nematode is established, grow resistant soybean varieties and keep the soil clean of weed hosts.
