Texas Cooperative Extension
Text and images copyright © Richard Duble.
Most specific disease problems are caused by only one pathogen and are
given a disease name such as brownpatch, dollar spot, or anthracnose that
reflects that pathogen. Until recently bermudagrass decline was thought
to be a complex problem caused by several disease organisms. No one had
been able to isolate any pathogen associated with these decline areas. Through
the correction of poor management practices the turf would recover slowly.
Pathologists in general considered the problem of declining bermudagrass
to be a complex management problem; hence, the name "bermudagrass decline."
Researchers working on this problem have isolated the disease organism from declining areas. Results of these isolations show that the fungus, Gaeumannomyces graminis, to be associated with these declining areas. The same organism, Gaeumannomyces, is the fungus associated with take-all patch in St. Augustinegrass.
Initial symptoms of bermudagrass decline include chlorotic patches of turf 8- to 24-inches in diameter. The turf thins out and may eventually be completely killed in these patches. Chlorotic leaf blades may develop next to green shoots at the margins of the diseased area. Roots of diseased bermudagrass are brown and without feeder roots and root hairs. Signs of the fungus on the root surface appear as dark brown hypal runners.
The disease occurs on weakened or damaged turf which indicates that management could be the key to control. If disease occurs, try to identify the predisposing factors and correct them through proper management practices. On golf greens, raising the mowing height is the most effective management practice to correct the problem.
The fungicide Rubigan is effective for the control of bermuda decline caused by Gaeumannomyces graminis. Since infection is thought to occur primarily in the fall, with disease progression continuing during the fall and winter months under cool moist conditions, fall applications may be the best time for fungicides to be applied for preventative purposes. It's efficacy in controlling the already established disease may be disappointing.