Powdery mildew is a fungal disease that occurs most commonly on the cool-season grasses such as bluegrasses and fescues. The fungus is usually first seen as isolated wefts of fine, gray-white cobwebby growth on the upper surface of the leaves. This growth rapidly becomes more dense, and may cover the entire leaf, giving it a gray-white appearance. In cases of severe outbreaks, entire sections of lawn may be dull white, rather than green. Disease