What to do when your Texas Lawn has Brown Patch

August 30, 2019

After a busy season of chinch bugs and crabgrass, the next problem will be a common fungal disease called Brown Patch.

brown patch of grass

This creative name describes the general symptoms caused by various ailments, whether it is chinch bugs, nematodes or the other numerous diseases that attack St. Augustine grass. One must investigate more closely to distinguish which culprit it might be. With brown patch disease, symptoms begin as 6-12 inch diameter “off color” patches that turn yellow, then reddish-brown, and then brown to straw-colored (see photo). These patches may merge and may expand several feet in diameter. Often, there may be rings of yellow/brown turf with green centers. Also, turf at the outer margin of an infected patch will be dark and wilted, this is the active zone of the pathogen as it spreads outward. To distinguish this fugal disease from other ailments, check the basal area of the leaf blades. This pathogen causes a black rot at the juncture of the stem and leaf blade.

This disease becomes active when temperatures drop below 80 degrees F., 73 degrees is optimum and, surprisingly, it is inactive during the hot humid summer conditions that one would typically think a fungus would thrive in. It shuts down when temperatures go above 90 degrees F. Infection occurs during periods of high humidity or excessive moisture for 48 hours or more. Soluble nitrogen fertilizer applications, greater than 1.1 pounds of actual nitrogen per 1000 sq. ft. put the turf at risk. Thatch buildup, more than 0.75 inch, also creates a disease favorable habitat.

What To Do:

  • Cutting your watering is a must during the fall. Your watering should be monitored to an as needed basis. Too often, we see customers use their irrigation systems as a set it and forget it tool. Water only when needed and do not trust your rain gauge unless you have tested it to be sure that it is working properly.
  • Do not self-diagnose your lawn. Most people see a yellowing area and immediately identify the area as a lack of water. More moisture could be the exact opposite of what it needs.
  • Be sure that your mower blades are sharp. Dull mower blades injure the plant, making it far more susceptible to plant diseases. It also allows more moisture to evaporate from the plant causing you to need more water which causes an increase moisture level in the soil leaving your lawn a prime environment for brown patch.