Disease Alert: Large Patch in Warm-Season Turfgrasses

Raleigh, North Carolina (April 4, 2007)--As the warm-season turfgrasses begin to green-up in the spring, symptoms of a disease called large patch often become evident. This 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 large patch.

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.

Fungicides are available for large patch control, but they are most effective when applied preventatively. The first application should be made in the late summer or early fall when soil temperatures decline to 70oF. One application will control minor cases of the disease, 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.