Summer Patch (fungus – Magnaporthe poae)
Host Grass: Bentgrass(Agrostis palustris), Fescue, Poa Series(Poa sp.)
Cause and Symptoms: Initially, summer patch resembles dollar spot but patches quickly grow and affect large areas of turf. Affected areas may appear dark green initially and then reddish-brown to bronze colored. As leaves die, turf becomes straw-colored in irregular patches, six inches to several feet in diameter. Occasionally, a frog-eye appearance is observed where turf is green in the middle of the patch. Summer patch is more severe on heat-stressed areas such as sunny, exposed slopes and areas adjacent to sidewalks and driveways. Environmental factors important to disease development are moist soils and root zone temperatures exceeding 75oF.
Control and Management: It is essential to have adequate nitrogen levels. Slow release forms of nitrogen have been shown to be more effective. DMI fungicides (triadimefon, fenarimol, propiconazole) are effective as preventive applications while thiophanate methyl soil drenches show some curative activity. Fungicides (See the section Chemical Controls for Turfgrass Diseases) are ineffective if turf is allowed to enter drought-induced dormancy.
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