What is Powdery Mildew?
Powdery mildew is a fungus that is most common in the fall on Kentucky Bluegrass grown in the shade. The turf will have a white or light gray appearance while the individual grass blades are covered with a white powdery coating. Powdery mildew is rarely responsible for damage to turf, although severe cases may make the grass look thin and yellow.
Optimum conditions for powdery mildew are moderate temperatures (55-70º F) with high humidity. Shade and poor air circulation along with slow growing turf increase the chances for powdery mildew.
Powdery mildew can be managed by both cultural and chemical controls. Cultural controls are preferable for sustaining disease-free turf. Select the correct grass type for the location. Use more shade tolerant turfgrasses such as fine fescues.
Increase light conditions by pruning trees and shrubs that may be shading the turf. Pruning the trees and shrubs will help with increased air circulation which will also minimize the occurrence of powdery mildew.
Though not generally recommended, fungicides may be applied for preventive control of powdery mildew. Fungicides help prevent the powdery mildew from spreading or getting established.