Gray Leaf Spot (fungus – Pyricularia grisea)
Host Grass: St. Augustine Grass(Stenatophrum secundatum)
Cause and Symptoms: Gray leaf spot develops rapidly with abundant moisture and warm temperatures on St. Augustine grass. It is especially troublesome in shaded areas that remain damp for some time. Under these conditions, the disease causes serious thinning of the turf. Leaf spots first appear as tiny brown to ash- colored spots with purple to brown margins that enlarge and become diamond-shaped. In severe cases, lesions develop on stems and spikes and the leaves wither and die. Turfgrass may have a burned or scorched appearance resulting from death or spotting of the leaf blades.
Control and Management : Avoid application of soluble nitrogen fertilizers on moderately shaded lawns during summer months. Apply water early in the morning only when water is needed. Avoid evening waterings which keep the leaf surface wet for long periods. Catch and remove grass clippings where gray leaf spot is a problem. Several fungicides (See the section Chemical Controls for Turfgrass Diseases) are recommended for gray leaf spot control.
Content edited by: Young-ki Jo, firstname.lastname@example.org , Assistant Professor and Extension Specialist, Dept Plant Pathology & Microbiology, Texas A&M University, Texas AgriLife Extension Service, May 31, 2013