What Is Brown Patch
Brown patch is a fungal disease caused by Rhizoctonia solani that attacks cool-season lawns during hot, humid weather (daytime temps above 85, nighttime above 65, with high humidity). It creates circular brown patches ranging from a few inches to several feet in diameter. The outer ring of the patch is often darker brown or gray, sometimes with a “smoke ring” visible in early morning dew.
How to Identify Brown Patch
Look for circular or semi-circular patches of tan-brown grass. Individual blades show tan lesions with dark brown borders. In morning dew, you may see a gray or white “smoke ring” at the expanding edge of the patch. The grass inside the patch is often still alive at the crown level; it looks dead from above but has green tissue at the base.
Treatment and Prevention
Cultural controls are the first line: water early morning only (not evening), avoid excess nitrogen in summer, mow at the proper height, and improve air circulation by pruning nearby shrubs. Fungicide treatment (azoxystrobin, propiconazole) provides 14 to 28 days of protection and is warranted for severe or recurring outbreaks. Apply at first sign of disease, not after extensive damage.
