Weather Favoring Brown Patch in Fescue Lawns

MANHATTAN, Kan. – Those mornings when dew is on the grass and temperatures are in the high 60s F or above, the fungus that causes brown patch disease goes into overdrive.

Brown patch affects several cool-season lawn grasses. But, tall fescue is especially susceptible, said Megan Kennelly, plant pathologist with Kansas State University Research and Extension.

“In warm, humid weather, symptoms can develop in 24 to 48 hours. The soil may be moist, but an infected lawn can look drought-stressed,” Kennelly said. “Diseased leaves turn a dark purple-green but quickly dry to a light tan or brown. They develop tan lesions with a brown border.”

The overall pattern of lawn damage can vary. Infected areas may be round patches of blighted turf, ranging from several inches to several feet across. More often, the damage is in irregular shapes, which sometimes look like a general browning of the lawn.

“Unless the infection is severe, most lawns can recover in two to four weeks. They just need the weather to change, so new, healthy leaves will emerge to cover the damage,” Kennelly said.

The brown patch fungus is a survivor. Most lawns already have plenty on hand, she explained. Fungicides to prevent and control the disease are available, too, but they can be costly. Some of the best aren´t labeled for homeowner use. Plus, the disease tends to emerge in Kansas when cool-season turfgrasses are growing very slowly. So, rescue treatments don´t always work well.

On the Web, Kennelly has posted the specific fungicides labeled for homeowner use at http://www.plantpath.k-

state.edu/DesktopModules/ViewDocument.aspx?DocumentID=1128.

“But, often the best defense is to manage turf so that conditions don´t favor the disease. You start by watering early in the morning, since evening irrigation brings long, disease-fostering periods of leaf wetness,” Kennelly said. “Also, select a resistant variety if you ever need to replant.”

K-State research has found that mowing often without a grass catcher can reduce lawns´ nitrogen needs by up to 20 percent. It also discourages disease, because the turf never gets overly tall, thus creating its own moist shade. Even infected turf´s clippings will not spread or foster brown patch.

“Don´t fertilize if you have active brown patch, though,” Kennelly said. “And, never apply more than the recommended amount. Excess nitrogen makes brown patch cases more severe.”