Photo by Ali Harivandi

Photo by A. H. McCain

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Hosts

Kentucky bluegrass, perennial ryegrass, tall fescue

Symptoms

Lawns damaged by southern blight have large, crescent to circular areas of damaged turf up to several feet in diameter. The turfgrass turns reddish-brown as it dies. Some plants may remain green in the center of the affected area. As the disease develops, white mycelia appear on grass blades and stems and light to dark brown sclerotia develop at the base of stems. The sclerotia, which resemble mustard seeds in size and shape, are key to diagnosing the disease.

Conditions favoring disease

Warm or hot temperatures (85° to 95°F), high moisture, and heavy thatch favor the development of southern blight. The fungus survives in the thatch as sclerotia.

Prevention and management

Follow proper irrigation and fertilization requirements for your turf species. Southern blight is less destructive on a vigorously growing grass. Control thatch. Use clean equipment when aerating or dethatching because these practices can spread the sclerotia. Fungicides may be useful in areas where the disease has been a problem in past years.

For more information on lawn diseases, refer to:
Pest Notes: Lawn Diseases: Prevention and Management