Bermuda Grass Blight

Disease Identification

• Bermudagrass blight is caused by the Pythium aphanidermatum fungus, the most common reason behind turf blights, notes the Texas A&M University Extension. The disease is also referred to as pythium blight, grease spot or cottony blight. Pythium blight attacks all cool- and warm-season grasses. The disease was first identified in 1954.

Favorable Conditions

• The fungus develops rapidly during humid weather and hot daytime temperatures ranging between 86 to 95 degrees F and nighttime temperatures of about 68 degrees F. Grass growing in low-lying areas, in poorly ventilated sites or on wet, poorly drained ground is more prone to infection. Fungus growth is also rapid following periods of excessive rain, extended dew periods and on excessively fertilized lawns with lush growth.

Symptoms

• Blight on Bermudagrass starts with the appearance of water-soaked, irregularly soaked, greasy-looking, 4-inch-diameter patches on lawn. A light, cottony growth is also visible on top of the patches during early morning in very humid weather. As infection progresses, the patches grow in size and merge to create large areas. Fungal spores or reproductive bodies spread to healthy lawn areas with lawn equipment and splashing water. Infected grass browns and withers into crater-like depressions in the ground.

Control

• Keep lawn adequately watered and avoid excessive irrigation, especially during hot, humid weather. Level any sunken lawn areas that are likely to collect water or that are poorly ventilated. Water lawns early in the morning and avoid the use of excessive nitrogen. Recommended fungicides for control include azoxystrobin, chloroneb, fosetyl-al, cyazofamid or mefenoxam.