Powdery Mildew on Shrubs: Identification and Control

Symptoms

White to gray powdery coating on leaves, stems, or flowers. Leaves may curl, yellow, brown, and drop prematurely. Usually not fatal but unsightly.

Management

• Cultural: Improve air circulation, avoid overhead watering, plant resistant varieties.
• Fungicides (apply at first sign):
  • Triadimefon (Bayleton, Strike)
  • Triforine (Funginex)
  • Thiophanate-methyl (Cleary's 3336)
  • Propiconazole (Banner)
• Spray thoroughly on both leaf surfaces, repeat every 7–14 days during cool, damp weather. Use a spreader-sticker.

On large trees, spraying may be impractical; mild infections often cause little harm.