Now's the Time to Prevent Large Patch in Warm-Season Turfgrasses

Raleigh, North Carolina (October 4, 2006) -- Recent periods of cool weather have triggered the development of large patch in warm-season turfgrasses across all of eastern and central North Carolina. Large patch is a common disease of centipede grass, St. Augustine grass, zoysiagrass, and bermudagrass grown for lawns, landscapes, golf turf, and athletic fields. Centipede grass and St. Augustine grass 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.

Large patch is encouraged by poor soil drainage, over-irrigation, excessive thatch, and nitrogen applications too late in the fall or too early in the spring. Proper turf management practices will help to minimize damage from this disease. Refer to the Management Calendar for your turf species on Turffiles for more specific recommendations.

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 70F or below. Depending on your location and weather patterns, this can be anywhere from late August to late September.

Determining your average daily soil temperature is easy: simply take the average of the high and low air temperatures for the day. This will provide a close approximation of soil temperature for your location.

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.

Fungicides containing the active ingredient triadimefon are very effective for large patch control and are available in garden centers and home improvement stores. Sprayable formulations of triadiemefon are more effective than spreader-applied granular products. Products containing azoxystrobin (Heritage) or flutolanil (ProStar) are also very effective but are generally only available to professional landscape managers.