Unexpected results reported during 2006 disease update

Surprising research results on gray leaf spot on turf and a new annual bluegrass disease were discussed at the PACE Turfgrass Research Institute's 10th Annual Turfgrass Research Seminar held last month in San Diego. Findings, presentations and handouts from the seminar are available on the PACE Member Edition's Web site (non-members may sample the Web site through a free three-week trial membership available at www.paceturf.org).

Dr. Frank Wong of the University of California addressed 145 turf managers in a presentation update on disease management. He said there were several areas in which his research yielded some unexpected results:

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  • The genetic diversity of gray leaf spot isolates from the western United States is much higher than had been expected, possibly indicating that the disease has either been introduced many different times, or that it has been present in the West longer than previously believed.

  • Gray leaf spot resistance to QoI fungicides (Heritage, Compass, Insignia) has been detected in the West, though it is not yet widespread.

  • For optimal control of gray leaf spot, Wong saw the best results when planting resistant varieties of perennial ryegrass (such as the variety Paragon), as well as tank mixes of contact fungicides (such as chlorothalonil or mancozeb) with systemics (such as Banner, Bayleton, Cleary's 3336, Compass, Heritage, Insignia).

  • A new Rhizoctonia-like disease has been causing problems on annual bluegrass in the West recently. The symptoms are similar to those caused by yellow patch, but unlike yellow patch, this disease occurs during warm weather. Genetic analysis indicates that the disease may be caused by Waitea circinata, a fungus that is closely related to Rhizoctonia. In preliminary lab tests, it was controlled best by Banner, Chipco 26GT and ProStar.

PACE Turfgrass Research Institute (PACE) is a membership organization that provides research, education and information services to the turf management community. Founded in 1993 by its research directors Wendy Gelernter, Ph.D. and Larry Stowell, Ph.D., the PACE mission is to generate and share independent and objective agronomic information among turf professionals so they may develop management programs that are effective, practical and scientifically sound.

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