Large patch favors cooler nights (9-7-09)

Labor Day has past and we will soon begin to see and feel those subtle changes from summer to fall. Daylight hours are becoming less 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. When temperatures begin to cool the potential for brown patch (Rhizoctonia solani) disease will increase. While most turf species can be affected by brown patch, it is the most prevalent disease of St. Augustine and centipede lawns during the spring and fall.

Brown patch is characterized by brownish to gray water-soaked irregular circular areas a few inches to several feet in diameter in the lawn. The disease usually attacks the base of leaf sheaths where they are joined to stolons causing the leaves to eventually die.

Another diagnostic symptom often found is 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 brown patch. Avoiding these will be wise. If your lawn has had a history of brown 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, 2009

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]