Golf Course Management

DEC 2013

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research many days pass before pathogen populations resume growth suffcient to cause symptoms. Fungicide rates and classes In this research each fungicide was applied at a single rate, representing the high rate prescribed on the product label. Our interest emphasized dissipation of different classes of fungicides rather than effects of application rates. Also, we could not evaluate all possible products or active ingredients in this research. The selected fungicides include representatives of important classes (especially QoI and DMI) for brown patch control. Given that residual effcacy is largely a function of microbial degradation over time, there is no reason (or existing evidence) to suggest that other fungicides within these classes would show a signifcant departure from the depletion curves shown here. Since microbial degradation is a function of temperature, the rate of depletion is expected to lessen during extended periods of low temperature (5). Interpretation The bioassay results, supported by analysis of fungicide residues in turf leaves and stems, clearly illustrate the rapid depletion of fungicide from turf beginning shortly after application. This pattern should be expected for all fungicides applied to turf. Results from this study help explain why fungicide treatments may not perform as expected during a given application interval and underscore the importance of applying fungicides in a timely manner for satisfactory disease control. Preventive applications that are delivered prematurely may dissipate before the arrival of environmental conditions that foster pathogen growth and promote disease outbreaks, leaving plants vulnerable to damage. The risk of disease-related damage as well as the cost associated with treatment reinforces the need to make informed management decisions concerning fungicide use. Superintendents should try to anticipate outbreaks and apply effective fungicides before disease development in order to achieve maximum fungicide performance, but they must also be aware of the rather short duration of effective residues in turf. Literature cited 1. Daniels, J., and R. Latin. 2013. Residual activity of fungicides for control of brown patch on creeping bentgrass. Plant Disease 97:1620-1625. 2. Fidanza, M.A., and P.H. Dernoeden. 1996. Brown patch severity in perennial ryegrass as infuenced by irrigation, fungicide, and fertilizers. Crop Science 36:1631-1638. 3. Frederick, E.K., M. Bischoff, C.S. Throssell and R.F. Turco. 1994. Degradation of chloroneb, triadimefon, and vinclozolin in soil, thatch, and grass clippings. Bulletin of Environmental Contamination and Toxicology 53:536-542. 4. Gardner, D.S., and B.E. Branham. 2001. Effect of turfgrass cover and irrigation on soil mobility and dissipation of mefenoxam and propiconazole. Journal of Environmental Quality 30:1612-1618. 5. Koch, P.L., and J.P. Kerns. 2011. Using ELISA to determine the effect of temperature on the degradation of the fungicides chlorothalonil and iprodione on golf course turfgrass. In: ASA-CSSA-SSSA 2011 International Annual Meetings [Abstracts]. Paper 67950. Online (https://scisoc.confex. com/crops/2011am/webprogram/Paper67950.html). Verifed Oct. 30, 2013. 6. Latin, R. 2006. Residual effcacy of fungicides for control of dollar spot on creeping bentgrass. Plant Disease 90:571-575. 7. Latin, R. 2011. A Practical Guide to Turfgrass Fungicides. American Phytopathological Society, St. Paul, Minn. 8. Magri, A., and D.A. Haith. 2009. Pesticide decay in turf: A review of processes and experimental data. Journal of Environmental Quality 38:4-12. 9. Wu, L., G. Liu, M.V. Yates et al. 2002. Environmental fate of metalaxyl and chlorothalonil applied to a bentgrass putting green under Southern California climatic conditions. Pest Management Science 58:335-342. GCM V v v The research says ➔ A bioassay study was carried out to determine how declines in fungicide residue affect disease control; quantitative analysis was used to measure the amount of fungicide remaining at each sample date. ➔ The results of this study indicate that fungicides are depleted rapidly beginning shortly after they are applied to turf. ➔ For four of the five fungicides, residual efficacy was reduced to 50% within three to five days. ➔ To achieve satisfactory disease control, superintendents should try to anticipate disease outbreaks and apply fungicides before disease develops. John Daniels earned his master's degree in plant pathology at Purdue University in 2012 and currently is the assistant golf course superintendent at Wheatley Hills Golf Club, East Williston, N.Y. Richard Latin (rlatin@purdue.edu) is a professor of plant pathology in the department of botany and plant pathology, Purdue University, West Lafayette, Ind. Acknowledgments This research was supported in part by funds provided to the Midwest Regional Turf foundations. The authors wish to extend their appreciation to David Bartlett, Bruce Cooper, Amber Jannasch, Douglas Richmond and Simon Perry for their technical expertise. December 2013 GCM 91

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