| Anthracnose | Fungus | Yellow/brown/purple/black spots on leaves; sunken, dark spots on stems; 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; 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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| Black rot | Fungus | Yellow, V-shape areas on leaf edges that brown and progress toward leaf center; leaves eventually collapse; stem cross sections reveal blackened veins | Destroy infected plants; choose resistant varieties; provide good drainage; remove plant debris; rotate crops |
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| Cabbage loopers | Insect | Large, ragged holes in leaves from larval feeding; defoliation; stunted or bored heads; excrement | Handpick; add native plants to invite beneficial insects; spray larvae with insecticidal soap or Bt; use row covers; remove plant debris |
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| Cabbage root maggots | Insect | Wilted/stunted plants; off-color leaves; larvae feeding on roots | Use collars around seedling stems; monitor adults with yellow sticky traps; use row covers; destroy crop residue; till soil in fall; rotate crops |
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| Cabbageworms | Insect | Leaves have large, ragged holes or are skeletonized; heads bored; dark green excrement; yellowish eggs laid singly on leaf undersides | Handpick; use row covers; add native plants to invite beneficial insects; grow companion plants (especially thyme); spray Bacillus thuringiensis (Bt) |
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| Clubroot | Fungus | Wilted/stunted plants; yellow leaves; roots appear swollen/distorted | Destroy infected plants; solarize soil; maintain soil pH of around 7.2; disinfect tools; rotate crops |
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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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| Downy mildew | Fungus | Yellow, angular spots on upper leaf surfaces that turn brown; white/purple/gray cottony growth on leaf undersides only; distorted leaves; defoliation | Remove plant debris; choose resistant varieties; ensure good air circulation; avoid overhead watering |
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| Flea beetles | Insect | Numerous tiny holes in leaves | Use row covers; mulch heavily; add native plants to invite beneficial insects |
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| Powdery mildew | Fungus | Typically, white spots on upper leaf surfaces expand to flour-like coating over entire leaves; foliage may yellow/die; distortion/stunting of leaves | 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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| Slugs/snails | Mollusk | Irregular holes in leaves; 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; 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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| Thrips | Insect | Leaves, especially in folds near base, have white patches or silver streaks; brown leaf tips; blistering/bronzing on cabbage leaves; curling or scarring | Remove plant debris; choose resistant varieties; add native plants to invite beneficial insects; use row covers; use straw mulch; monitor adults with yellow or white sticky traps; use sprinklers or other overhead watering |
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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 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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