- any of various parasitic fungi of the ascomycete order Erysiphales, which produce a powderlike film of mycelium on the surface of host plants.
- a disease caused by powdery mildew, characterized by yellowing and death of the foliage and a white mealy growth of fungus on the surface of above-ground parts.
- a plant disease characterized by a superficial white powdery growth on stems and leaves, caused by parasitic ascomycetous fungi of the family Erysiphaceae: affects the rose, aster, apple, vine, oak, etc
- any of the fungi causing this disease
