February 2017

SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.

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14 SportsTurf | February 2017 FIELD SCIENCE Figure 2.* Effect of fraze mowing height and manganese applications on SDS severity. Velista fungicide is a broad spectrum SDHI (Succinate Dehydrogenase Inhibitor – FRAC Group 7) that protects against several turfgrass diseases including SDS. Velista binds with SDH inhibiting a critical respiratory pathway preventing spore germination and mycelia growth necessary for infection. Getting fungicides to the point of infection is critical when working with soil-borne diseases such as SDS. As expected, Velista fungicide applications consistently reduced SDS severity compared to the untreated control. A numerical increase in fungicide control was also observed with an increase in fraze mowing depth from 0 to 0.32 inches (Figure 3). Figure 3*. Effect of fraze mowing height and fungicide application on SDS severity. In combination treatments of nitrogen source, manganese, and fungicide, SDS was numerically reduced with an increase in the fraze mowing depth (Figure 4). While there were no significant differences, the correlating trend of less SDS with increased fraze mowing depth provides further evidence that thatch/organic matter removal and subsequent rhizome and stolon regeneration could be an important part of disease control. Figure 4. Effect of fraze mowing height, nitrogen source, manganese and fungicide on SDS severity. No significant differences among treatments. While fraze mowing still provides many other benefits of thatch removal, weed seed removal, and a clean spring transition of bermudagrass athletic fields by promoting new growth, the practice may also serve as a tool to reduce spring dead spot severity. As evidenced in our first trial, fraze mowing is not a stand-alone practice for control of SDS, but instead should be looked at as a component of an overall management program. As with most research, this work has led to more questions. Can aggressive fraze mowing with a fungicide alone be all that is needed? Does it become a multi-year approach? Is fraze mowing necessary every year? Continued work at the University of Missouri and other institutions will hopefully provide an answer to these questions and more as the new practice of "fraze mowing" becomes more standard and widespread. *Bars with the same letter are not significantly different according to Fisher's Protected LSD test. Brad Fresenburg, PhD, is Extension Turfgrass Specialist, Division of Plant Sciences – University of Missouri. Lee Miller, PhD, is Associate Professor Turfgrass Pathology, Division of Plant Sciences – University of Missouri. Daniel Earlywine is Research Technician, Division of Plant Sciences – University of Missouri. References are available online at Several research trials have indicated hollow-tine aerification or other cultivation methods may reduce SDS severity and increase fungicide efficacy.

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