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

March 15, 2005

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