Fungal diseases that attack fruits, vegetables, flowers, and grasses. The primary symptom is a white to purple, downy growth, usually on the underside of leaves and along stems, which turns black with age. Upper leaf surfaces have a pale color. It can overwinter on infected plant parts and remains viable in the soil for several years. It is spread by wind, rain, and in seeds. To control, thoroughly compost sick plants and apply cornmeal to the soil surface.