PACE Turf - Turfgrass Information Center

Diseases

Evaluation of Fungicides and Wetting Agents for the Management of Localized Dry Spot and Fairy Ring

Summary: In a replicated field trial conducted on a bentgrass (Pennlinks) practice putting green at Del Mar Country Club, Rancho Santa Fe, CA, the wetting agents Respond and Primer and the fungicides Heritage and ProStar were evaluated for their ability to control localized dry spot (LDS) and fairy ring caused by the fungus Agrocybe pediades. Key results included:

  • The fungus Agrocybe pediades, which produces small brown mushrooms, was identified from non-treated plots. This fungus is frequently associated with fairy ring symptoms in Southern California.
  • Two types of symptoms were detected in the plots: 1) Type B fairy ring symptoms: dark green circles of stimulated turf growth, with thatch degradation leading to low spots in the turf, and 2) Type C fairy ring (also frequently called localized dry spot) symptoms: dry spots with irregular areas of dead or dying turf and extreme hydrophobicity underneath.
  • Respond G and Primer significantly reduced the incidence of LDS (Type C fairy ring) symptoms. However these products applied by themselves had no effect on the incidence of Type B fairy ring symptoms.
  • Both Type B and Type C fairy ring symptoms were controlled best by monthly applications of ProStar (6 oz/1000 sq ft) plus the wetting agent Respond (3 oz/1000sq ft) (no posttreatment irrigation) and by monthly applications of Heritage (0.4 oz/1000 sq ft) plus the wetting agent Respond L (3 oz/1000 sq ft) (with post-treatment irrigation). Performing almost as well were monthly applications of Heritage (0.4 oz/1000sq ft), with or without post-treatment irrigation, and Heritage plus Respond (with no posttreatment irrigation).
  • It is important to note that while wetting agents can manage the symptoms of LDS (as can cultural practices such as verticutting, aerification, topdressing and hand watering), a fungicide such as ProStar or Heritage is necessary to kill the fungus that causes dry spot and fairy ring.
  • For reasons that are not clear, turf phytotoxicity occurred when monthly applications of ProStar (6 oz/1000 sq ft) were made without the addition of Respond L. This appears to be a unique observation, since ProStar is typically applied on golf courses, including Del Mar Country Club, under these same conditions with no negative results. We are working with AgrEvo to better understand this effect.

Printable version of full report

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

Cooperator: David Major, Del Mar Country Club

Sponsors: Mike Fidanza, AgrEvo, David Bower, UHS and Jim Petta, Zeneca

 

Evaluation of ProStar and ProStar Plus for Control of Fairy Ring on Golf Course

Summary: Both ProStar (6 oz/1000 square feet) and ProStar Plus (7.5 oz/1000 square feet) provided good to excellent curative control of fairy ring caused by Agrocybe pediades on a bentgrass green. A thirty day application interval resulted in control equal to that with a 15 day application interval. The addition of Bayleton to ProStar, in the form of ProStar Plus, did not improve the control offered by ProStar alone. In addition, ProStar Plus caused some reduction in turf quality. Applications were not followed by irrigation, a factor which may have aided in control.

Printable version of full report

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

Cooperator: David Major, Del Mar Country Club

Sponsor:  Dale Comer, AgrEvo

Characterization and Management of Bermudagrass Decline on Golf Course Greens

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.

Printable version of full report

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

 

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