Powdery mildew is primarily a problem on Kentucky bluegrass turf growing in partial shade or in areas with poor air circulation. The disease is most often found in the spring and fall when days are cloudy and nights are cool and damp. The disease appears as a white to light gray powdery growth on the upper surfaces of leaves and leaf sheaths. It spreads rapidly in shaded areas and the powdery growth becomes increasingly dense. The lower leaves of Kentucky bluegrass may be completely covered by the powdery growth.
Infected leaves turn yellow, become tan or light brown and gradually shrivel and die.
Repeated infestations of the disease results in greatly reduced growth and eventual death of plants. Surviving plants often remain in a weakened condition. Reduced shading and increased air circulation will help control powdery mildew. Where these conditions cannot be changed, fungicides are available for control. Acti-dione RZ, Banner and Bayleton are fungicides labeled for control of powdery mildew.