Brown Patch Disease on Lawns
Brown Patch disease (Rhizoctonia spp.) occurs in Maryland in warm, humid weather. The combination of daytime temperatures that are over 85°F and nighttime temperatures that stay above 65° F with little air flow leaving the grass moist for over eight hours are the perfect conditions for this turf disease. You can identify Brown Patch by its symptoms. Light tan lesions with dark brown edges across the middle or tips of the grass blades are signs you might have Brown Patch. On mornings with abundant dew, you will actually be able to see the signs of the fungal mycelium which look like cottony structures.
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It is mainly a problem on improved varieties of Tall Fescue. If you have a variety that is especially susceptible to Brown Patch disease and the ideal environmental conditions are expected for an extended period of time, you might need to have your lawn treated with a fungicide to avoid having to. However, if a cold front is expected within a few days to lower the humidity and nighttime temperatures, it may not be necessary to spray.
If you suspect you have brown patch, avoid nighttime watering if you can. Afternoon and evening showers and thunderstorms on a humid night set up the ideal conditions for Brown Patch disease. More information on Brown Patch UMD
Please let us know if you have any questions about this disease.
Mark Schlossberg is the President of ProLawnPlus in Baltimore, MD. He graduated from the University of Maryland in 1977 with a B.S. in agronomy. He is the President of the Maryland Association of Green Industries, and past president of the Maryland Turfgrass Council.