Late fall, winter and early spring. Cold wet weather. High humidity and temperatures from 32 to 45 degrees F. Snow cover provides an ideal environment for the development. Pale yellow irregularly circular patches. Affected areas change color to a whitish gray.
Individual leaves take on a bleached appearance and feel slimy when wet.
Spring, summer and fall. Cool wet weather. The center becomes a depressed gray area with an almost black ring around the edges. . Kentucky bluegrass, bentgrasses, ryegrasses, tall fescue and creeping red fescue. Most common when temperatures are ranging from 80 to 90 and there are extended periods of rain.