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 |
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
|
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 |
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 |
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) |
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 |
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 |
Flea beetles |
Insect |
Numerous tiny holes in leaves |
Use row covers; mulch heavily; add native plants to invite beneficial insects |
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 |
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 |
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 |
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 |