With soil temperatures starting to approach 70°F across portions of NC, now is the time to start thinking about treating for large patch.
Large patch, which is caused by the fungus Rhizoctonia solani, is a common disease of centipedegrass, St. Augustinegrass, zoysiagrass, and bermudagrass grown for lawns, landscapes, golf turf, and athletic fields. Centipedegrass and St. Augustinegrass are particularly susceptible to this disease.
Symptoms of large patch appear in roughly circular patches from 2 feet up to 10 feet or more in diameter. The affected turf will initially be orange, yellow, or reddish-brown in color but will then turn tan and collapse to the ground. The disease can spread rapidly to encompass large areas of turf, and distinct circular patches may not be obvious in these cases.
Fungicides are available for large patch control, but they must be applied preventatively for best results. The first application should be made in the late summer or early fall when average daily soil temperatures are 70°F or below.
One fungicide application will control minor cases of large patch, but two to three applications on a 4 to 6 week interval may be needed to control severe cases. Fungicides are not very effective once the symptoms of large patch appear. Curative applications will help to reduce further spread of the disease, but the affected turf will be very slow to recover.
For more information about Large Patch, including images and specific control recommendations: http://www.turffiles.ncsu.edu/
By Lee Butler
September 19, 2012