• Worldwide distribution. On crops, ornamentals, weeds in many families: cotton, cucumber, onion, legume, potato, and more. Common and potentially serious fungal disease.
• Lower leaves infected first with whitish powdery patches on undersides, yellow irregular spots above. Unlike other powdery mildew: little fungal growth over the leaf surface.
• Spread by spores on the wind.
• Cultural control: nursery: avoid overcrowding; weed; check plants before planting. Field: remove volunteers; do not overapply N; avoid moisture stress; choose areas with good air movement; resistant varieties.
• Chemical control: commercial plantings: i) wettable sulphur, ii) chlorothalonil, or iii) triazoles. Organic regime: horticultural oil, potassium bicarbonate or wettable sulphur.(oils are eradicants). Apply wettable sulphur early morning or evening. Never within 2 weeks of the last application of an oil spray. READ LABEL. If few plants: use normal strength milk diluted 1 part in 10 parts of water.

Tomato powdery mildew

Leveillula taurica. Other names are Erysiphe taurica and Oidium sicula. It exists as different strains. There are other powdery mildews affecting tomato. They are: Oidium lucopersici and Oidium neolycopersici.