Brown patch is a fungal disease that affects tall fescue, perennial ryegrass, Kentucky bluegrass, bentgrass, bermudagrass, zoyziagrass and St. Augustinegrass.
Brown patch develops rapidly as a result of prolonged wet conditions (i.e. periods of rain, heavy dew, excessive irrigation or poor drainage) when the air temperature is sufficiently warm (75 to 85 degrees Fahrenheit). Over-fertilization during the late spring or summer can also promote disease development. Additionally, lawns with excessive thatch (decaying plant matter between the grass and soil) are known to be more susceptible to disease because the thatch provides an excellent environment for fungi.
Turfgrass infected with brown patch is, at first, a dark purplish-green which fades to light brown. Circular brown patches of turf develop that are a few inches to several feet in diameter. The discolored grass blades within the circle have a sunken or flattened appearance. Some healthy, unaffected grass may exist within the diseased area.
A similar disease called cool-season brown patch, or yellow patch, occurs during cool, wet weather. Distinct rings of yellow-green to brown grass surrounds healthy-appearing grass. Due to the confusing nature of turf patch diseases, an inspection with your local arborist is necessary to diagnose and determine treatment options.
Fungicide treatments along with proper plant health care will help reduce the severity of brown patch.
Two to three fungicide treatments may minimize reoccurring damage if the brown patch infection is severe. Results with fungicide applications will be better if cultural controls are also followed:
- Avoid over-fertilization with quick-release sources of nitrogen
- Do not apply nitrogen fertilizer when the disease is active
- Reduce watering: if necessary, water only in the early morning
- Consider aeration to reduce thatch
- Increase light penetration and air movement by selective pruning of trees and shrubs
- Maintain the proper mowing height, and frequently sharpen the blade