Golf Course Management

FEB 2019

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

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02.19 GOLF COURSE MANAGEMENT 69 accumulated for that day would be 10. e HDD accumulation for each site began on July 1 of the respective year. Snow mold pressure was high in all three years in Minocqua; unfortunately, it was the only site to experience significant snow mold in any year of the study. e Minocqua re - sults provide a strong indication that there is a sharp cutoff in the efficacy of fungicide tim - ing under heavy disease pressure. Disease was sharply reduced in 2017 and 2018 (and to a lesser extent in 2016) when Instrata was ap - plied four or more weeks before the first signif- icant snowfall (Figure 1). In 2016-2017, con- trol improved dramatically between the Oct. 13 and Oct. 31 applications and an HDD ac - cumulation of 24 (Oct. 13) and 130 (Oct. 31) (Figure 2). In 2017-2018, control improved dramatically between the Oct. 16 and Nov. 1 applications and an HDD of 43 and 176. Using only the Minocqua data, it appears that an HDD of approximately 100 can be used to effectively time applications of Instrata for snow mold control. Soil temperature was not an effective predictor of snow mold fungicide timing because of the large variation experi - enced from year to year (Figure 3). Additional locations need to be evaluated to determine how applicable this HDD number is for a broader area. We intend to continue this study over more locations to determine whether an HDD-based model can be effective in timing snow mold fungicides. Conclusions and future directions e results of the fungicide timing study clearly demonstrate that timing of fungicide applications targeting snow mold plays a criti - cal role in effective snow mold control. Apply- ing snow mold fungicide applications based solely on the calendar may lead to ineffective snow mold control depending on the envi - ronmental conditions present that particular fall. However, during our study, only one site provided enough disease pressure to assess im - pacts of fungicide timing. erefore, the ap- plicability of the results to a wider audience remain inconclusive. After we obtain more data over the next two to three years, we will look to test our HDD-based application model at numerous golf courses across Wisconsin and the upper Midwest to determine the model's efficacy. In addition, other products aside from In - strata will need to be evaluated to determine whether the results obtained from Minocqua Fungicide timing study at Timber Ridge Golf Club in Minocqua, Wis. The most effective control was achieved when fungi- cide was applied less than four weeks before snow cover. Snow mold severity (2016-2018) after fungicide treatment (2015-2017) 100 90 80 70 60 50 40 30 20 10 0 NTC Sept. 1 Sept. 15 Oct. 1 Oct. 15 Nov. 1 Pre-snow 2016 2017 2018 Approximate fungicide application timing Typhula blight severity (%) Accumulation of HDD for Minocqua, Wis., 2015-2017 500 450 400 350 300 250 200 150 100 50 0 Sept. 1 Sept. 15 Oct. 1 Oct. 13 Nov. 2 Pre-snow 2015 2016 2017 Heating degree days Figure 1. Snow mold severity follow- ing applications of Instrata at 9.3 fluid ounces/1,000 square feet at various times throughout the fall at Timber Ridge Golf Club, Minocqua, Wis. The pre-snow treat - ment was made on Nov. 16 in 2015, Nov. 17 in 2016 and Nov. 14 in 2017. Figure 2. Accumulation of heating degree days (HDD) for Minocqua, Wis., during 2015, 2016 and 2017. The pre-snow treat - ment was made on Nov. 16 in 2015, Nov. 17 in 2016 and Nov. 14 in 2017.

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