The fungus (Rhizoctonia solani), commonly known as brown patch or more recently referred to as large patch, is the most troublesome lawn disease for many Mississippi lawns. While this disease attacks most lawn turf species it is most serious on St. Augustine and centipede lawns in the spring and fall.
Visual symptoms are brownish to gray irregular circular patches of a few inches to several feet in size. These water-soaked or scalded spots spread rapidly often with a narrow smoke-colored ring bordering the diseased area. The fungus generally attacks the base of leaf sheaths where they join to the stolons. When the disease is most active these leaves slip easily from the stolons when pulled on and have a brown, wet, slimy decay at the base.
Brown patch is most severe when temperatures moderate at night in the upper 50 and 60 degree range with midday temperatures in the 70’s. Once summer temperatures get into the 80 and 90 degree range, disease activity ceases until fall.
Brown patch activity is enhanced by high nitrogen fertilization, moisture on the leaf surfaces, and excessive thatch. Therefore, to diminish the incidence of attack be judicious with spring fertilization, particularly with fertilizers high in water soluble nitrogen, water early enough in the day to allow foliage to dry before nightfall, and maintain good mowing practices to manage thatch buildup. When brown patch becomes severe applications of fungicides may be necessary.
For more information on brown patch and other lawn diseases refer to Extension Publication Establish and Manage Your Home Lawn which can be obtained from your local Extension Service office or on the MSU Extension Web site.
Published April 18, 2005
Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. email@example.com