Characterization and Management of Bermudagrass Decline on Golf Course Greens

March 15, 2005

Summary: In replicated field trials conducted on a bermudagrass putting green, fungicides were tested for efficacy and phytotoxicity against symptoms of bermudagrass decline, caused by Gaeumannomyces graminis. Key results include:

Summer temperatures that were significantly cooler than normal contributed to a lack of disease pressure at this site. Weak decline symptoms (irregularly shaped chlorotic patches, with both roots and foliage affected) were observed in the non-treated plots, and the presence of Gaeumannomyces was confirmed microscopically. However, damage due to disease in the non-treated plots was not significantly worse than in fungicide treated plots.
As a result of lack of disease pressure, it was not possible to judge the products tested for their efficacy in controlling symptoms of bermudagrass decline.
Applications of the sterol inhibitor fungicide Eagle produced significant phytotoxicity, probably as a result of a maximum air temperature of 100°F on the day of application. In contrast, the sterol inhibitor tebuconazole (Lynx) did not produce any significant signs of turf damage, nor did any of the other fungicides tested. These observations are similar to those reported from Florida by Elliott (1995). In contrast, results of several years of fungicide evaluations on poa/bent greens indicates that Eagle is one of the safest products to use on cool season turf, while tebuconazole applications resulted in significant phytotoxicity to Poa annua.
With the possibility of Eagle induced phytotoxicity on bermudagrass greens indicated in trials from Florida and California, it is recommended that this product be reevaluated next summer in a variety of locations to further investigate this phenomenon.
Bermudagrass decline caused by Gaeumannomyces graminis var. graminis appears to be an increasing problem on greens. Background information on this disease appears at the end of this report.

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Principal Investigators: Wendy Gelernter, Ph.D. and Larry J. Stowell, Ph.D.

Cooperator: Nancy Dickens, Sun City West, Palm Desert, CA

Sponsors: Bayer, Novartis, Rohm and Haas, Zeneca