Powdery mildew of Grasses

Hosts. All turfgrass species, but Kentucky bluegrass and perennial ryegrass are most susceptible.
Symptoms. Leaf surfaces are covered with a grayish white powdery growth. Isolated patches may spread to larger areas of the lawn. Leaf blades may turn pale yellow in later stages of the disease.
Conditions favoring disease. Cool temperatures (about 65°F), high humidity, and poor air circulation favor the development of powdery mildew. The disease is most severe in shady areas.
Prevention and management. Reduce shade and improve soil aeration. In areas where powdery mildew is a problem, plant less susceptible species. Follow proper irrigation and fertilization recommendations for your turf species. Mow at the high end of the recommended height for your species. Fungicides are usually not warranted.