Brown Patch

David Koon & Amy Winstead

Brown patch is the most damaging disease of warm season turf grasses in Alabama. St. Augustinegrass, zoysiagrass, and centipedegrass are most susceptible to this disease; common and hybrid bermudagrasses are rarely damaged.

Excessive nitrogen fertility levels and thatch often lead to outbreaks of brown patch. The disease usually develops on lawns during periods of wet, overcast weather in late spring or fall. Damage is often heaviest after several days of showers with day temperatures of 60° to 80°F and heavy cloud cover.

Brown patch first appears in lawns as small, circular, brown areas several inches in diameter, which quickly increases to 3 to 6 feet. These areas often grow together, forming irregular patches of brown, blighted turf up to 20 feet in diameter.

Nitrogen fertility has a significant impact on brown patch development. High nitrogen levels promote the growth of soft, succulent leaves that are susceptible to attack by the brown patch fungus. To help prevent disease outbreaks, apply a low rate of a nitrogen fertilizer at 4- to 8-week intervals through the growing season, or use a slow-release nitrogen source to maintain an even growth rate.

Outbreaks of brown patch are usually too sporadic, especially on home lawns, to justify a preventive fungicide spray program. Limit preventive treatments to portions of those lawns that have previously been damaged by this disease.

Make applications only when weather conditions favor the spread of disease. The time interval between applications varies between 10 and 21 days, depending on the fungicide used. On most home lawns, a fungicide spray program should begin as soon as symptoms appear and continue until the turf starts to recover or until weather conditions no longer favor the spread of disease. For best results, apply fungicides at 5- to 7-day intervals to the diseased area and to a 1- to 2 foot border.

For more information on brown patch or a list of fungicides labeled for use on home lawns, contact the local Alabama Cooperative Extension System Office in your county.

Posted by smithkp at May 6, 2005 01:59 PM