Our Horticulture Consultants in the Diagnostic Lab are seeing common turfgrass problems that occur this time of year, Dollar Spot (Sclerotinia homoeocarpa) and Brown Patch (Rhizoctonia spp.). If you suspect your lawn may have one of these diseases, there are cultural control practices you can use to manage the problem.

Dollar Spot is indicative of the dead straw-colored spots about the size of a silver dollar and may persist from early summer until early fall. Its incidence seems to be higher in seasons with low rainfall and occurs on bluegrasses, bentgrasses, fescues, and zoysia. Symptoms depend largely on mowing practices. Under close mowing conditions the circular straw-colored spots are distinctly outlined in the early stages of disease development. With higher cutting heights, the bleached turf spots are irregularly shaped. In the early morning when dew is still on the grass, a white cobwebby growth of the fungus may be seen over the spot. To manage, mow grasses at the recommended maximum height. Try not to remove more than 1/3 of the leaf surface in any one mowing. Maintain adequate soil moisture, but avoid sprinkling in the late afternoon or evening, and do not overwater.

Dollar Spot

The patterns of symptoms for Brown Patch depends largely on cool vs. warm season grasses, mowing practices and moisture levels. On cool season grasses the symptoms produced by a Rhizoctonia sp. infection may vary depending on the maintenance practices. Under close mowing conditions, cool season grasses that are kept very wet produce small, blighted patches that appear quickly during optimum conditions. The patches may contain a purplish-gray border that is referred to as a “smoke-ring”. Cool season grasses that are cut high and kept dry may produce patches up to 30 cm in diameter. Cultural control recommendations include reducing thatch, removing dew from the leaf blades and providing good drainage conditions. Additionally, fertilizer applications should be monitored to ensure nitrogen levels are adequate but not excessive. Excessive nitrogen can increase disease occurrence and severity.

Brown Patch

To determine if your lawn has Brown Patch or Dollar Spot, you can call or submit a lawn sample to our Diagnostic Lab. Contact information and forms with instructions on how to submit soil samples and plant, insect, tick and lawn problems can be found at http://ccesuffolk.org/gardening/horticulture-diagnostic-labs

Photos courtesy of Tamson Yeh, Pest Management/ Turf Specialist, CCE Suffolk County. Article adapted from Cornell Cooperative Extension of Suffolk County Horticulture Diagnostic Lab fact sheets Dollar Spot on Turfgrass and Brown Patch on Turfgrass.