The beauty of a lawn can be quickly destroyed by brown patch (Rhizoctonia solani), a serious fungal disease that can affect a variety of turf grasses. It can develop rapidly when temperatures are warm (75 to 90 °F) and humid, especially on cool season grasses (fescue, ryegrass, bluegrass and bentgrass). It can also occur on these grasses during warmer periods of the winter months. Warm season grasses (St. Augustinegrass, zoysiagrass, Bermudagrass and centipedegrass) most commonly are affected by brown patch during the early spring and late fall, however they are generally more resistant to brown patch.
Symptoms:
Symptoms of brown patch may vary greatly with the type of grass and soil conditions. The disease usually causes thinned patches of light brown grass that are roughly circular in shape. These areas range in diameter from a few inches to several feet. Close inspection of cool season grass blades reveals small, irregular, tan leaf spots with dark-brown borders. Bentgrass may not show individual lesions, but leaves will turn brown and shrivel. Infected warm season grasses rarely have leaf spots but instead have rotted leaf sheaths near the soil surface.
Conditions resulting in proliferation of brown patch activity include:
- Areas with poor air circulation
- Prolonged wetness of turf
- Dull mower blades
- High nitrogen (when disease is already active)
- Soil compaction