Brown patch fungus is caused by a fungal pathogen (Rhizoctonia solani) that affects all cool-season turfgrass species. It is a foliar disease that does not affect crowns or roots. Moderate to severe outbreaks can result in thin, poor quality turf that may be predisposed to algae and moss infestation. Even mild brown patch fungus outbreaks can spoil the appearance of turf greens. Brown patch fungus is really a summer lawn disease that’s caused by a fungus called Rhizoctonia. The disease begins to show growth when temperatures reach 65°, but the most active growth of brown patch fungus lawn disease occurs at temperatures of 80-85° when humidity levels are very high.
What is Brown Patch Fungus?
Under favorable environmental conditions, brown patch symptoms can develop overnight. On Tall Fescue brown patch fungus development results in circular olive green stains, ranging from 4 to 12 inches in diameter (Figures 1 ).
Leaf-blades within the patch turn brown after infection, while a gray-white band is normally evident at the perimeter of active patches (Figure 2). The band (often called a smoke ring) is caused by advancing mycelium and watersoaked infected leaves. Smoke rings may occur on taller mown turf like Tall Fescue but are much less evident. Individual lesions on leaf blades with brown margins occur on all affected grass species but are most evident on tall fescue (Figure 3).
•Brown patch fungus is characterized by the development of irregular, circular areas a few inches to several feet in diameter.
•These areas will usually appear as brownish to grayish patches.
•These areas can spread rapidly throughout a fescue lawn when humid, warm, moist conditions exist.
What Causes Brown Patch Fungus?
Watering during the afternoon and early evening. Watering at this time can cause brown patch fungus issues because in high humid areas you want to cut down on the time your grass spends wet/humid in heat. At night the water sits longer on the grass and is not absorbed faster. So mix this with high humidity it encourages brown patch fungus and/or disease.
Heavy Thatch layers– Several turfgrass pathogens can survive in the thatch layer, including those that cause summer patch, leaf spot, and melting-out diseases. Heavy thatch may also lead to fairy ring problems. Bermuda grass, Kentucky bluegrass, and kikuyugrass produce more thatch than most other turfgrasses and require regular dethatching.
Infrequent mowing- Maintaining a lawn at the recommended mowing height will improve its ability to resist diseases and give it a greater aesthetic appeal. The frequency with which the lawn is mowed should be based on the growth rate of the grass. Lawns should be mowed often enough so that no more than one-third of the length of the grass blade is removed at any time. Removing too much of the grass blade can increase the susceptibility to several diseases by depleting food reserves in the plant, making it difficult for the plant to recover from stress and injury.
Dull mower blades- Maintain sharp mower blades to avoid mechanical damage to turf. Dull mower blades rip the grass blade instead of cutting it clean which opens up the grass blades to diseases like brown patch fungus.
All Tall fescue is susceptible to brown patch fungus.
How to reduce the risk of Brown Patch Fungus?
Proper watering and mowing practices.
Keeping your lawn at a good height and making sure that you are aerating and seeding yearly.
Establish a good fertilization and weed control program.