Area Lawns Being Troubled by Fungal Disease

The UGA Extension Gwinnett office has received numerous calls from residents concerned about dead spots appearing on their lawns. In most cases the cause is a fungal disease. The conditions have been favorable for their development in the past couple of weeks. The warm days, cool nights and abundant moisture have caused these diseases to become problematic.
    The most common one is brown patch and large patch diseases, which are both caused by the same fungus, Rhizoctonia solani. Brown patch attacks cool season grasses such as tall fescue. It also causes leaf spots and "smoke rings" -- thin, brown borders around the diseased patches, which are one to two feet in diameter. The symptoms are most frequently observed in the early morning.The disease is more prevalent during the summer months. Remember cool season grasses thrive in cooler weather and can suffer stress during the heat of our summers. It also causes leaf spots and "smoke rings" -- thin, brown borders around the diseased patches that appear most frequently in the early morning.

        Brown patch disease attacks cool season grasses, such as tall fescue.  

               Photograph by Lee Miller, University of Missouri  

    Large patch disease affects warm season grasses such as bermudagrass, zoysiagrass and centipedegrass. It has a some what different appearance than brown patch. the rings are considerably larger, two to ten feet in diameter. On the outer edges, a light brown to orange color appears. Sometimes the fungus can come back year after year in the same location. It occurs on the leaf sheaths forming a reddish brown to black water soaked lesions. The foliage dies back from the top to the base of the blade. Large patch disease is more prevalent in the fall and spring, but is also troublesome during the summer. 

Large patch disease attacks warm season grasses such as bermudagrass.
Photograph by Barb Corwin, Turfgrass Diagnostics

   For control, avoid applying too much high nitrogen fertilizer on the lawn, which promotes the fungus. Have you soil tested through UGA Extension Gwinnett and fertilize according to recommendations. Water earlier in the day before noon to allow for the grass to dry before the evening. Make sure you mow your lawn at the correct height, and the blade is sharpened. A dull mower blade shreds the ends of the grass making them more susceptible to pests and gives it an off-color appearance. Aerate with a hollow tine aerator of your lawn has not been done so in the past three years.
   Fungicides can be applied according to label directions to help suppress the fungus and reduce its ability to spread. Examples include Spectracide Immunox and the Bayer Advanced and Ortho products.