This fungus was initially reported as a disease of sorghum, but has since been found to also cause a problem on bent grasses. It is relatively rare in Pennsylvania.
On the leaves of turf grass plants, the disease first appears as small reddish lesions, which soon enlarge and becomes dark red. Blighting of the entire leaf soon results as these lesions merge.
The disease, seen from a distance, first appears as a copper-colored patch, 1 to 3 inches in diameter. Intensity of this coloration increases during wet weather, due to the pink spore masses which are produced. Cooper spot is often confused with dollar spot; the latter has a bleached, straw-colored appearance. Both diseases may occur simultaneously in the same stand of turf grass.
Cooper spot is primarily a warm, wet, weather disease; active growth begins when temperatures reach the 70 to 75 range. The fungus spores are spread by splashing water, germinate rapidly, and cause new leaf lesions to appear within a relatively short period of time.