Cooler weather may incite large patch outbreaks (09-04-2006)

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. Subtle changes going on with our lawns as well and when temperatures begin to cool the potential for large patch also known as brown patch (Rhizoctonia solani) disease will increase. While most all 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 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 so avoiding these will be wise. Do not apply fertilizers containing high levels of quick release sources of nitrogen in the fall if your lawn has had a history of large patch attack. Water the lawn early enough in the day to allow the leaves to dry before nightfall and 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 recovery will not be possible until the following spring.

Published September 4, 2006

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