Golf Course Management

JUN 2018

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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06.18 GOLF COURSE MANAGEMENT 75 CUTTING EDGE Teresa Carson Pesticide, turfgrass guttation and pollinators Golf course turfgrasses provide a unique water source to pollinators in the form of xylem sap or guttation fluid. is phenom - enon, in which plant foliage exudes droplets containing metabolites, nutrients and drink - able water, can be witnessed in all types of grasses but varies in seasonal availability and quantity. Golf course irrigation practices allow for continuous, bountiful production of turf - grass guttation fluid, providing an optimal water source for pollinators. Unfortunately, water-soluble active ingredients within pes - ticides can be absorbed and transported sys- temically in the grass via the xylem; they can then be released back into the environment in concentrated titers via the guttation-fluid re - lease mechanism. e objective of this work is to determine the bioactivity of commonly applied demethylation inhibitors (DMI) and strobilurin fungicides and DMI plant growth regulators (PGRs) in turfgrass guttation fluid, and to identify the potential hazards they may pose to pollinators (honey bees) and other beneficial insects. We aim to assess and ana - lyze the titers of DMI (fungicides and PGRs) and strobilurin (fungicide) in turfgrass gutta - tion water collected from golf course greens and from rough areas where DMI and stro - bilurin pesticides are applied. We will deter- mine the LD50 value of DMI and strobilurin fungicides and of a DMI PGR for European honey bee (Apis mellifera) exposed to gutta - tion water collected from turf treated with the aforementioned pesticides. — Audrey Simard (asimard@wisc.edu) and R. Chris Williamson, Ph.D., University of Wisconsin-Madison Prediction model advises fungicide applications for dollar spot control Controlling dollar spot typically requires numerous fungicide applications in a single growing season. Earlier dollar spot predic - tion models were largely ineffective and are not currently in widespread use. Our primary objective was to develop a new weather-based dollar spot prediction model to more accu - rately advise when to make fungicide appli- cations to control dollar spot activity across a broad geographic and climactic range. e new model, the Smith-Kerns dollar spot pre - diction model, was recently published in the peer-reviewed journal PLOS One and was developed from data collected at field sites in Madison, Wis., and Stillwater, Okla., in 2008. e model was validated in the field from 2011 to 2016 at sites in Madison, Wis.; Stillwater, Okla.; Knoxville, Tenn.; State Col - lege, Pa.; Starkville, Miss.; and Storrs, Conn. A meta-analysis of all sites and years was con - ducted, and the most effective model for dol- lar spot development consisted of a five-day moving average of relative humidity and av - erage daily temperature. e model produces a probability that dollar spot will occur on a given day, and the highest probability that provided an effective spray threshold for dol - lar spot control across all sites and years was 20%, though this may change depending on local environmental factors. Additional anal - ysis in Madison, Wis., found that the 20% spray threshold provided control comparable to a calendar-based fungicide program while reducing fungicide usage by up to 30%. e Smith-Kerns model can aid in making more accurate dollar spot fungicide applications based on the environmental conditions. For more information and for tools to implement the Smith-Kerns model, visit https://tdl.wisc. edu/dollar-spot-model/ . — D.L. Smith, Ph.D., University of Wisconsin-Madison; J.P. Kerns, Ph.D., North Carolina State University, Raleigh; N.R. Walker, Ph.D., Oklahoma State University, Stillwater; A.F. Payne, Oklahoma State University, Stillwater; B. Horvath, Ph.D., University of Tennes - see, Knoxville; J.C. Inguagiato, Ph.D., University of Connecticut, Storrs; J.E. Kaminski, Ph.D., Penn State University, State College, Pa.; M. Tomaso- Peterson, Ph.D., Mississippi State University, Mis - sissippi State; and P.L. Koch, Ph.D. (plkoch@wisc. edu), University of Wisconsin-Madison. Teresa Carson (tcarson@gcsaa.org) is GCM 's science editor. Photo by Paul Koch Photo by Audrey Simard

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