AZ Master Gardener Manual: Key to Specific Vegetables (Onion and Pea)

PLANT PATHOLOGY: DIAGNOSTIC KEY [continued]

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MG Manual Reference
Ch. 4, pp. 11 - 12

[ 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

ONION

SYMPTOMS	CAUSES	CONTROLS
Numerous small white flecks on leaves; leaves die from tips back and turn brown	• Botrytis blast	• Use registered fungicide
	• Downy mildew (fungal disease)	• Use registered fungicide
	• Onion thrips	• Use registered insecticide
White flecks form on leaves and expand into elongated leaf lesions; white to purplish mold develops on spots during moist weather leaves drop over and dry up	• Downy mildew (fungal disease)	• Rotate; use registered fungicide
Leaves yellow and die back from tips; bulbs are soft and rotted	• Fungal or bacterial bulb rot	• Rotate; remove old plant debris; plant in well drained soil
Dark green or black smut up to 1 inch in diameter on bulb or neck	• Smut (fungal disease)	• Rotate; remove old plant debris; plant in well drained soil; plant disease-free onion sets
White streaks or blotches on leaves	• Onion thrips	• Use registered insecticide

PEA

SYMPTOMS	CAUSES	CONTROLS
Plants stop producing pods; leaves turn yellow, then brown and die	• Hot weather	• Peas are cool season vegetables: plant early in spring; plant heat resistant varieties
	• Root rot (several fungi)	• Rotate; plant in well drained soil; remove old plant debris
	• Fusarium wilt (fungal disease)	• Resistant varieties; rotate; remove old plant debris
Plants stunted; lower leaves yellowed; internal stem tissue discolored brown	• Fusarium wilt	• Resistant varieties; rotate; remove old plant debris
	• Waterlogged soil	• Improve drainage
White, powdery mold develops on upper and then lower surfaces of leaves; leaves and pods may be distorted	• Powdery mildew (fungal disease)	• Rotate; remove old plant debris
Brown spots on leaves, pods, stems	• Fungal or bacterial disease	• Submit sample for diagnosis
Yellowish areas on leaves; blister- like ridges on undersides of leaves and on pods; pod distortion	• Pea enation mosaic virus	• Resistant varieties; weed control; insect control; remove affected plants
Light-colored leaf veins; rosetting of shoot tips; plants stunted with poor pod set	• Pea stunt virus	• Weed control; insect control; remove affected plants

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