A fungus has been wreaking havoc this summer and fall in lawns across the state. According to turfgrass pathology results from our Plant Disease Laboratory at the University of Georgia, a disease called take-all patch, caused by the fungal pathogen Gaeumannomyces graminis var. avenae, is the culprit.
Initial symptoms are circular to irregular straw-color to light-brown thinning patches from 6 inches to 3 feet in diameter. As the disease progresses, patches might come together, eventually killing large areas of the lawn. The patches can reappear in subsequent years causing extensive damage.
Take-all patch is sometimes confused with brown/large patch (caused by Rhizoctonia solani) because of similar symptoms. These two diseases can be distinguished from each other by pulling on a yellow or brown blade of grass. The blade infected with brown patch will give some resistance when pulled on.
Turf infected with take-all patch will easily pull from the ground. The stolon infected with brown patch will not be brown/black as with take-all patch.
Root rot from take-all patch causes affected stolons to be easily pulled from the ground. Roots will be blackened and shortened.
Maintaining a pH below 6.5 will reduce the severity of the disease. If your soil pH is above 6.5, acidifying fertilizers such as ammonium sulfate can be used to lower it. Manganese deficiency also increases the severity of take-all, so supplements of this can be added. A good fertilizer with micronutrients will contain manganese.
Fungicides have limited effectiveness after the disease has shown up. They are much more beneficial when applied preventively, but the average homeowner doesn't treat until a problem is visible.
Like most diseases, take-all patch is associated with stressed lawns. Management for this disease involves good cultural practices such as:
- Good surface and subsurface drainage. Core aerating a lawn in the spring can help.
- Water infrequently but deeply.
- Proper fertilization. This depends on turf species and site conditions (sunny or shady). Centipede, for example, should receive only one pound of nitrogen per growing season.
- Proper mowing height for your grass.
- Avoiding application of herbicides to damaged areas of the lawn. For example, St. Augustine does not have a high tolerance for herbicides. This was especially true this year with such a bad chinch bug problem and the grass was already weakened.
Dr. Phillip Colbaugh, of Texas A&M, has found that applying a sphagnum peat moss topdressing to St. Augustine reduces symptoms of take-all patch in lawns. The recommendation is 3.8 cubic feet of sphagnum peat moss per 1,000 square feet.
Applications in fall and early spring of fungicides are most effective. Immunox Lawn Disease Control (myclobutanil), and Bayleton or Bayer Advanced Fungus Control for Lawns (triadimefon) are all registered to help manage take-all patch.
Sid Mullis is the director of the University of Georgia Extension Service office in Richmond County. Call (706) 821-2349, or send e-mail to email@example.com.