Problem: Powdery Mildew (Lawns)
This lawn disease is caused by a fungus (Erysiphe graminis) and occurs whenever the nights are cool (65° to 70°F) and damp and the days warm and humid. It is most severe on Kentucky bluegrass but also attacks fescues and bermudagrass. Lawns growing in the shade are the most affected. Powdery mildew slows the growth of leaves, roots, and underground stems, causing gradual weakening of the grass and making the grass more susceptible to other problems. Lawns growing rapidly because of excessive nitrogen fertilization are very susceptible to attack from this fungus. The fine white mildew on the blades develops into powdery spores that spread easily in the wind.
Reduce the shade and improve air circulation by pruning surrounding trees and shrubs. Follow recommended lawn care practices for a healthy, vigorous lawn.