Powdery Mildew is a common disease on Kentucky bluegrass, fine fescues, and Bermuda grass. The fungus causes this disease. The white powdery growths develop on the leaf surfaces in the spring and early fall.
Powdery Mildew on leaf surface. Picture by B. Fresenburg
Most of the infections occur in the shady portions of the landscape. When shaded areas have poor air circulation, high humidity levels, and moderate temperatures then an outbreak of powdery mildew is inevitable.
The best way to control this disease is to use good cultural practices. Plant shade tolerant grasses in shady areas. Prune or remove woody plants to allow better air circulation and light penetration. Avoid excessive Nitrogen fertilization. The turf in the powdery mildew-prone sites should be cut at a higher height than surrounding turf.
Fungicides can be used, but are not generally recommended. If necessary fungicide should be sprayed before symptoms are noticed because most fungicides are preventative, and they generally prevent the starting and spread of disease.