Growth is enhanced by low light levels that accompany cloudy or foggy periods. Cannot survive if there is a film of water on leaves or stems. The best time to examine plants is early in the morning while dew is on the leaves. The first symptom is sunken, water-soaked spots on leaves, either yellowish or grayish in color. Spots later become covered with a downy purplish mold growth which may eventually be blackened by a second fungus.
Infected leaves become covered with a grayish-white powdery fungus growth.
Unopened flower buds may be white with mildew and never open. Leaves will become brown and shrivel when mildew is extensive. Fruits ripen prematurely and have poor texture and flavor. Wash both upper and under surfaces of the leaves. Do in early afternoon because that is when spores are most likely to be moving on air currents.