Large patch is most prevalent spring disease of Southern lawns (4-19-10)

The fungus (Rhizoctonia solani) commonly known as large patch (also referred to as brown 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.

Large patch is most severe when temperatures moderate at night in the upper 50 and 60 degree range with midday temperatures in the 70’s and low 80’s. Once summer temperatures get into the upper 80’s and higher disease activity ceases until fall. Visual symptoms are brownish to gray irregular circular patches often with a narrow smoke-colored ring bordering the diseased area. These water-soaked or scalded spots can spread rapidly from a few inches to several feet in size. The fungus generally attacks the base of leaf sheaths where they join to the stolons. When the disease is most active, infected leaves may slip easily from the stolons when pulled on and display a brown, wet, slimy decay at their base.

Large 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 large patch becomes severe fungicide applications may be necessary. For more information on large patch and other lawn diseases refer to Extension publication #1322 "Establish and Manage Your Home Lawn" which can be obtained from your local Extension Service officeb.

Published April 19, 2010

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. wwells@ext.msstate.edu