The beauty of your lawn can be quickly destroyed by brown patch (Rhizoctonia species), a serious fungal disease that can affect all lawn grasses used in our area. It develops rapidly when temperatures are warm (70° to 90° F) and humid during the day and cool significantly at night. Warm-season grasses such as St. Augustine, Bermuda, and Zoysia are most commonly affected by brown patch during the early spring and late fall.

Symptoms of brown patch vary greatly with the type of grass and soil conditions. The disease usually causes thinned patches of light brown grass that are fairly circular in shape. These areas range in diameter from a few inches to several feet. Sometimes the center of the patch will recover, resulting in a doughnut-shaped pattern.

When disease conditions are favorable, large areas of the lawn may be uniformly thinned and eventually killed with no circular patch being present. This type of pattern is commonly seen on infected St. Augustine grass grown in moist and shady locations.

The best way to prevent brown patch in your lawn is by following good lawn care practices. This is more effective, much easier and less expensive than the use of fungicides.

Combat Brown Patch (Rhizoctonia)

  • Irrigate grass only when needed and to a depth of 4 to 6 inches.
  • As the temperatures begin to cool cut back watering so that the ground is moist but not ever soggy or standing in water.  It is crucial to decrease the time and “run days” of your irrigation system proportionately to falling temperatures, and adjust it zone by zone according to the sun and wind exposure and the type of plants within that zone.  Use of the seasonal controller, if your system has one, is recommended.   Our irrigation experts can assist you in determining the ideal irrigation schedule for your lawn.
  • Water early in the morning so that any excess water can evaporate.
  • Brown patch can spread very rapidly when excess moisture is present.Keep lawns mowed on a regular basis to the proper height for the grass species you are growing.
  • Prevent excessive thatch buildup.
  • Provide good drainage for both surface and subsurface areas. Aeration can help provide good drainage.  For optimum results aerate twice a year in March and September/October.
  • Avoid high nitrogen rates on warm season grasses in mid to late fall. The brown patch fungus readily attacks the lush growth of grass which nitrogen promotes.

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