Research Summaries Rapid Diagnostic Tool for Improved Spring Dead Spot Recommendations
Yellow Nutsedge Control with Combinations of Halosulfuron and Sulfentrazone
Virginia Tech Researcher: David McCall, Turfgrass Pathologist, and Elizabeth Bush, Plant Diagnostician
Virginia Tech Researchers: Jeffrey Derr, Ph.D., and Adam Nichols, Virginia Tech
Research Sponsors: USDA-NIFA Extension IPM Program
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pring dead spot is easily the most common and destructive disease of bermudagrass turf. The depressed voids left behind are not only unsightly, but also they can potentially be an injury hazard on athletic playing surfaces. Two species of Ophiosphaerella are known to incite disease in our region. O. korrae is the dominant species in the Carolinas and other southeastern states, while O. herpotrica is more prevalent in Maryland, Kentucky and throughout the Midwest. Previous research has documented that each species can be successfully managed with different nitrogen sources. After three years of field testing in Virginia, our results have not been as clearly defined. With Virginia being in the transitional area of predominant species, we hypothesize that populations are mixed in most locations, preventing us from being able to develop sound recommendations. In collaboration with the Plant Diseases Clinic at Virginia Tech, we are working to develop a rapid diagnostic procedure for identifying the pathogen to species. In 2013, intensive sampling of our four test sites around the state will provide insight into variability within a site. Future samples will be submitted from across Virginia and surrounding states to develop a geographic distribution of species for more precise recommendations. Spring dead spot on Tifway 419 bermudagrass.
Research Sponsors: Gowan Company, the Virginia Turfgrass Council and the Virginia Turfgrass Foundation
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edgeHammer, which contains the active ingredient halosulfuron, provides effective postemergence control of yellow nutsedge, but it is slow acting. Dismiss, which contains sulfentrazone, works much faster than SedgeHammer, but it often does not provide as effective long-term control as SedgeHammer. We wondered if a combination of the two herbicides might result in both rapid and effective long-term control of yellow nutsedge. The objective of our research was to determine the efficacy of combinations of halosulfuron and sulfentrazone on the control of yellow nutsedge (Cyperus esculentus). The efficacies of these treatments were rated for control of yellow nutsedge versus SedgeHammer and Dismiss applied alone, and an untreated control. Treatments containing sulfentrazone caused more injury to yellow nutsedge at 2 days after treatment (DAT) than those lacking sulfentrazone. At 15 DAT, however, adding halosulfuron at 1 oz. product per acre to sulfentrazone at 8 fl. oz. product per acre reduced yellow nutsedge control compared to Dismiss at 8 fl. oz. per acre applied alone. By 23 and 65 DAT, though, no significant differences were observed among the herbicide treatments. Long-term control was similar among the treatments. Adding halosulfuron to sulfentrazone appeared to reduce the rapid action of sulfentrazone, although long-term sedge control was unaffected. So, there may not be any benefit to combining these two herbicides. Additional trials are needed to verify this conclusion.
Yellow Nutsedge and Southern Crabgrass Control with Combinations of Halosulfuron with Quinclorac or Fenoxaprop Virginia Tech Researchers: Jeffrey Derr, Ph.D., and Adam Nichols, Virginia Tech Research Sponsors: Gowan Company, the Virginia Turfgrass Council and the Virginia Turfgrass Foundation
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sed for control of yellow nutsedge, dallisgrass, crabgrass and other turf weeds, MSMA is currently being phased out for turf use, with current products labeled only for golf, sod production and highway rights of way. With the future uses of MSMA in turf unclear, alterna-
28 | Virginia Turfgrass Journal May/June 2013 www.vaturf.org