Individual blades look like they have been dusted with flour.
Closer inspection reveals a white, powdery growth primarily on the upper surface of the leaves.
As the disease progresses, turfgrass blades wither and die. Kentucky bluegrass grown in the shade is the most likely to be affected. Disease normally occurs in August to September. Fertilization will often allow the turf to outgrow the disease. Since this disease often appears in late August, fertilization is a good choice.