Anthracnose | Fungus | Yellow/brown/purple/black spots on leaves; sunken, dark spots on stems and pods; spots may develop a salmon-pink, gelatinous mass; eventually, rot | Destroy infected plants; choose resistant varieties; provide good drainage; avoid overhead watering; apply compost; use mulch; rotate crops |
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Aphids | Insect | Misshapen/yellow leaves; distorted flowers/pods; sticky “honeydew” (excrement); sooty, black mold | Grow companion plants; knock off with water spray; apply insecticidal soap; put banana or orange peels around plants; wipe leaves with a 1 to 2 percent solution of dish soap (no additives) and water every 2 to 3 days for 2 weeks; add native plants to invite beneficial insects |
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Cucumber beetles | Insect | Holes in leaves/flowers; rasped pods; plants stunted/die; may transmit bacterial wilt | Handpick; mulch heavily; use row covers; destroy plants infected with bacterial wilt |
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Cutworms | Insect | Wilting; severed stems of seedlings and transplants just above or below soil line; whole seedlings disappear | Handpick; in spring before planting, cultivate soil to reduce larvae; wrap a 4-inch-wide collar made from cardboard or newspaper around each stem, sinking 2 inches into soil; weed; use row covers; destroy crop residue |
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Japanese beetles | Insect | Leaves skeletonized (only veins remain); stems/flowers/pods chewed; grubs feed on roots | Handpick; use row covers |
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Leafhoppers | Insect | White shed skins on leaf undersides (from nymph molting); stippling (many tiny spots) on leaves; “hopperburn” (leaves yellow/brown, curled, or stunted); reduced yield | Knock nymphs off leaf undersides with strong spray of water; use row covers; monitor adults with yellow sticky traps; weed; destroy crop residue |
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Mexican bean beetles | Insect | Lacey, skeletonized foliage; dark holes on pods | Handpick; purchase and release beneficial wasp Pediobius foveolatus when larvae observed; destroy severely infested plants; use row covers |
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Mosaic virus (bean) | Virus | Leaves show green mottling (mosaic pattern) and may be distorted, blistered, curled downward; plants stunted | Destroy infected plants; choose resistant varieties and certified virus-free seed; use row covers; disinfect tools; weed; control aphids |
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Powdery mildew | Fungus | White spots on upper leaf surfaces expand to flour-like coating over entire leaves; foliage may yellow/die; distortion/stunting of leaves/flowers | Destroy infected leaves or plants; choose resistant varieties; plant in full sun, if possible; ensure good air circulation; spray plants with 1 teaspoon baking soda dissolved in 1 quart water; destroy crop residue |
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Root-knot nematodes | Nematode | Typically, roots “knotty” or galled; plants stunted/yellow/wilted | Destroy crop residue, including roots; choose resistant varieties; solarize soil; add aged manure/compost; disinfect tools; till in autumn; rotate crops |
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Slugs/snails | Mollusk | Irregular holes in leaves/flowers; gouged pods; slimy secretion on plants/soil; seedlings “disappear” | Handpick; avoid thick bark mulch; use copper plant collars; avoid overhead watering; lay boards on soil in evening, and in morning dispose of “hiding” pests in hot, soapy water; drown in deep container filled with 1/2 inch of beer, or sugar water and yeast, and sunk so that top edge is slightly above ground; apply 1-inch-wide strip of food-grade diatomaceous earth as barrier |
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Stinkbugs | Insect | Yellow/white blotches on leaves; scarred, dimpled, or distorted pods; shriveled seeds; eggs, often keg-shape, in clusters on leaf undersides | Destroy crop residue; handpick (bugs emit odor, wear gloves); destroy eggs; spray nymphs with insecticidal soap; use row covers; weed; till soil in fall |
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White mold | Fungus | Pale gray, “water-soaked” areas on stems, leaves, and other plant parts that enlarge and develop white, cottony growth, later with black particles; bleached areas; crowns/pods rot; plants wilt/collapse | Destroy infected plants; ensure good air circulation; water in morning; weed; destroy crop residue; rotating crops on 5-year or longer cycle may help |
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Whiteflies | Insect | Sticky “honeydew” (excrement); sooty, black mold; yellow/silver areas on leaves; wilted/stunted plants; distortion; adults fly if disturbed; some species transmit viruses | Remove infested leaves/plants; use handheld vacuum to remove pests; spray water on leaf undersides in morning/evening to knock off pests; monitor adults with yellow sticky traps; spray with insecticidal soap; invite beneficial insects and hummingbirds with native plants; weed; use reflective mulch |
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Wireworms | Insect | Seeds hollowed; seedlings severed; stunting/wilting; roots eaten | Trap by digging 2- to 4-inch-deep holes every 3 to 10 feet, fill with mix of germinating beans/corn/peas or potato sections as bait, cover with soil or a board, in 1 week uncover and kill collected wireworms; sow seeds in warm soil for quick germination; provide good drainage; remove plant debris; rotate crops |
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