Humidity and excessively wet conditions can create the perfect opportunity for brown patch to develop during the summer months.
The fungus develops during the hot, wet, and humid weather patterns and affects all turf grasses. Tall fescue and lush cool-season lawns are especially vulnerable.
The disease creates round or irregular patches in shades of tan to brown that can range in size from 6″ to 2′. The outer edge of the patch may be darker in color. Upon closer inspection you will see irregularly shaped dark lesions on the leaves and a gray to white fungal growth when the turf is wet.
Environmental influences include daytime temperatures in the 80s to mid90s, warm nighttime temperatures in the mid 60s and above, and abundant rainfall. Overly irrigated areas, wet soils with poor drainage, shaded turf areas, and turf areas with little or no air movement are more susceptible to developing the disease.
There are dozens of products labeled for the preventive and/or curative control of brown patch. Always check labels for restrictions. The disease will often subside when weather conditions are cooler and dryer.
To reduce the risk of brown patch there are several cultural practices you can implement:
Avoid excessive fertilizer, especially in the summer. Several light applications are less likely to trigger the disease than one heavy application.
Keep lawns mowed to avoid excessively tall grass.
Improve air flow by pruning or removing overgrown trees and shrubs.
Water lawns early in the day to allow turf to dry quicker and allow the soil to dry out between waterings.