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PLANT PATHOLOGY: DIAGNOSTIC KEY [continued]

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  MG Manual Reference
Ch. 4, pp. 4 - 5
[ Diagnostic Key: vegetables | specific vegetables; asparagus, bean, beet, carrot, cole crops, corn, cucurbits, eggplant, lettuce, onion, pea, pepper, potato, tomato | tree fruits| specific fruits; apple, stone, citrus | ornamentals | specific ornamentals; rose family, rose, palm, pine ]


KEYS TO PROBLEMS ON SPECIFIC VEGETABLES

BEAN Top

SYMPTOMS CAUSES CONTROLS
Plants wilt or are stunted; leaves turn yellow • Dry soil • Supply water
• Root rot (fungal disease) • Remove old plant debris; rotate; plant in well drained area
• Root knot nematode • Rotate; soil pasteurization
• Poor fertility • Amend soil as needed
Failure to set pods • High temperatures, causing blossoms to drop  
• Dry soil • Supply water
• Wet soil, causing lack of oxygen to roots • Do not overwater; plant in well drained soil
• Mature pods left on vines, causing seed production rather than pod set • Pick pods regularly
Rust-colored powdery spots surrounded by yellow haloes form on leaves, stems, and pods • Rust (fungal disease) • Resistant varieties; use registered fungicide; remove old plant debris
Soft, watery spots on leaves, stems, and pods; white moldy growth on these plant parts; plants wilt and die • White mold (fungal disease) • Use registered fungicide; rotate; remove old plant debris; plant in well-drained and ventilated area not planted to beans last year
Thin, white powdery growth on leaves and pods • Powdery mildew (fungal disease) • Resistant varieties; use registered fungicide; rotate; remove old plant debris
Small, brown spots surrounded by yellow haloes on leaves: leaves wither • Halo blight (bacterial disease) • Avoid overhead watering which spreads the disease; use fixed copper bactericide if available locally
Leaves skeletonized; copper-colored beetle with black spots or yellow grubs with spines • Mexican bean beetle • Hand pick the beetles and grubs or use registered insecticide
Leaves with shiny white spots • Spider mites • Use insecticidal soap spray or registered miticide
Young leaves curled, distorted, and yellow; clusters of tiny insects on leaves and stems • Aphids • Use registered insecticide or hard stream of soapy water

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