Cooler days signals the return of large patch (9-7-10)

Labor Day has past and we will soon begin to see and feel those subtle changes from summer to fall. Daylight hours are shorter and there is that hint of crispness in the air when picking up the morning paper. There are some subtle changes going on with our lawns as well and when temperatures begin to cool the potential for large patch (Rhizoctonia solani) disease will increase. While most turf species can be affected by large patch, it is the most prevalent disease of St. Augustine and centipede lawns during the spring and fall.

Large patch, also commonly referred to as brown patch, is characterized by brownish to gray water-soaked and irregular circular areas that are a few inches to several feet in diameter. The disease usually attacks the base of leaf sheaths where they are joined to stolons causing the leaves to eventually die. Another diagnostic symptom is often found when pulling by hand on individual leaf blades. They easily slip from the stolon and have a brown, wet, slimy appearance at the base. If the disease becomes severe and is not controlled it will eventually attack the stolons and roots killing large areas of the lawn.

Excessive nitrogen fertilization, leaf wetness, and heavy thatch build up tend to make the turf more susceptible to large patch. Avoiding these will be wise. If your lawn has had a history of large patch attack be on the alert and be prepared to treat with an appropriate fungicide early before the fungus becomes devastating to the lawn. Control is particularly important in the fall as the turf will not have sufficient recovery time before it goes dormant. Weakened thin areas in the lawn now and throughout the winter will only lead to more problems in the spring.

Published September 7, 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. [email protected]