Dollar Spot – Small Brown Patch (fungus – Sclerotinia homeocarpa)
Host Grass: Hybrid Bermuda(Cynodon dactylon), Common Bermuda, Bentgrass(Agrostis palustris), Centipede Grass, Fescue, Zoysiagrass(Zoysia japonica)
Cause and Symptoms: Bentgrass, hybrid bermudagrasses and zoysiagrass are most susceptible to dollar spot. Disease occurs from late spring through fall and is most active during times of warm humid days (70oF to 85oF) and cool nights (60oF). Water, mowers and other equipment or shoes spread the fungus. On fine textured and close-cut turf, round, bleached out or straw-colored patches occur which are sunken and approximately the size of a silver dollar. In coarse textured or high-cut turf, the dead spots are larger and more diffuse. Under these conditions, dollar spot is sometimes confused with brown patch. Characteristic spots on leaf blades readily distinguish dollar spot from brown patch. Light tan spots with reddish-brown borders radiate from the edge of the leaf blade. These spots may cover the width of the leaf. When the disease is active, cobweb-like mycelium of the fungus can be seen growing on affected areas early in the day before dew dries.
Control and Management: Remove excess thatch. Maintain proper fertility and adequate soil moisture. Aerate compacted soils. Remove morning dew by poling, irrigating or mowing. Choose a less susceptible turfgrass. Dollar spot seldom damages St. Augustine and centipede grasses. Fungicide applications (See the section Chemical Controls for Turfgrass Diseases) are most critical during moist weather in spring and fall when day temperatures are between 70oF and 80oF.
Content edited by: Young-ki Jo, email@example.com , Assistant Professor and Extension Specialist, Dept Plant Pathology & Microbiology, Texas A&M University, Texas AgriLife Extension Service, May 31, 2013