While most fungi thrive in moist surroundings, the organisms causing powdery mildew flourish in dry conditions; they also prefer warm days, cool nights, and shade. The various members of the group attack different hosts and survive from year to year on perennial plants.
Many plants like cucurbits, roses, phlox, dahlias, beans, peas, grapes, small fruits and fruit trees, euonymus, and bluegrass lawns.Damage:
Gray or white circular patches appear on leaves; then whole leaves become powdery white and distorted. Infected leaves may drop, and the entire plant may be weakened or killed. The flavor of peas, squash, and melons may be affected.Control:
Resistant varieties, good air circulation, sanitation, pruning, misting, fungicides.Notes:
Since dry air favors the disease, mist susceptible plants. Spray with fungicide when symptoms first appear. Prune off and destroy infected tissue.