It appears as cottony-white to tan fungal colonies and yellowed blotches on the upper and lower surfaces of the leaves. It develops more severely on the lower leaves but it can infect any of the leaves in cool, humid weather. When the disease is severe, the peas are stunted, turn yellow, and defoliate. A lush stand of peas is an ideal environment for powdery mildew development. Dew formation and lack of rainfall also favour the development of the disease.
Rain showers are actually disruptive to the spread of powdery mildew.
The inoculum is spread by wind. Once it is established, powdery mildew increases very rapidly. Symptoms of Damage Symptoms consist of a light, greyish, powdery growth on the leaves, pods and occasionally on the stems. This powdery growth is easily rubbed off. As the plant ages, tiny fruiting bodies of the fungus often form in the powdery growth.