Powdery or downy mildews are flour-like patches on the surface of leaves, buds, young stems, and fruits. They cause dwarfing, stunting, and deformation. The mildews are common on roses, zinnias, phlox, lilacs, cucurbits, apples, and grapes in shaded, crowded areas.
To control, avoid crowding to improve air circulation and reduce shade. Control weeds that harbor the disease. Apply recommended fungicides.
