Golf Course Management

FEB 2019

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68 GOLF COURSE MANAGEMENT 02.19 application was made one month before snow cover. Neither of these studies directly investi - gated fungicide timing and uptake, however, and the lack of recent research on both issues, and the importance of those issues to a large number of superintendents, make them prime candidates for further research. e objectives of this project were to determine the rate and degree of propiconazole uptake into turfgrass leaves at 72 F, 57 F, 50 F and 34 F (22.2 C, 13.8 C, 10 C and 1.1 C) and to determine the most appropriate application timing for effec - tive snow mold control at various field sites throughout Wisconsin. Plant uptake of propiconazole Plant uptake of propiconazole was mea- sured on Penncross creeping bentgrass es- tablished in an artificial growth medium in growth chambers on the University of Wis - consin campus. A single seed was planted in each container and maintained at a 2-inch (5 cm) cutting height under optimal growth conditions (14-hour photoperiod, 70 F [21.1 C] temperature, 55 F [12.7 C] nighttime temperature) for eight weeks until the plants matured. e plants were then moved to four growth chambers represent - ing different temperatures and day lengths throughout the fall: 72 F with a 12-hour pho - toperiod, 57 F with an 11-hour photoperiod, 50 F with a 10-hour photoperiod, and 34 F with a nine-hour photoperiod. Two weeks following placement in each growth chamber, plants received 1 milliliter of propiconazole (Banner Maxx, Syngenta) ap - plied in deionized water at a concentration of 1,624 micrograms of propiconazole per mil - liliter of water. is concentration is roughly equal to that of 2.0 fluid ounces of Banner Maxx diluted in 1.5 gallons of water/1,000 square feet. e propiconazole was applied di - rectly to the soil at the base of the plant using a pipette, and individual plants were measured 24, 48 and 96 hours after the application. At each time point, the plants were cut into three different sections (0-0.44 inch [0-1 centime - ter], 0.44-0.78 inch [1-2 centimeters], and 0.78-1.18 inches [2-3 centimeters] above the soil surface) and frozen until propiconazole analysis could take place. Significant variability was observed be - tween replicates and runs of the propiconazole uptake study, which made results difficult to interpret (Table 1). However, it was clear that much less propiconazole was detected in the 0.44- to 0.78-inch and 0.78- to 1.18-inch por - tions of the leaf blade relative to the 0.44- to 0.78-inch portion. is was evident no matter the temperature and no matter the time after application. In addition, almost no propicon - azole was detected in the upper leaf portions (0.44-0.78 inch and 0.78-1.18 inches) in the 34 F growth chamber relative to the other growth chambers. is suggests that upward mobility is lim - ited at colder temperatures, which is not sur- prising given the transpiration-based move- ment of propiconazole. However, it remains unlikely that lack of fungicide movement in the plant xylem applied to dormant turf sig - nificantly reduces the efficacy of the product. For example, in our research at the Univer - sity of Wisconsin, we have applied snow mold research trials to completely frozen turf on numerous occasions and observed excellent control with penetrant products under heavy disease pressure. Field trials for optimal timing of snow mold fungicides Field trials to determine optimal timing were conducted during the winters of 2015- 2016, 2016-2017 and 2017-2018 at three sites throughout Wisconsin that traditionally ex - perience low, moderate and high snow mold pressure. e low-pressure site was the OJ Noer Turfgrass Research and Educational Fa - cility in Madison, Wis.; the moderate-pressure site was Greenwood Hills Country Club in Wausau, Wis., (and, later, Bull's Eye Coun - try Club in Wisconsin Rapids, Wis.); and the high-pressure site was Timber Ridge Golf Club in Minocqua, Wis. Seven treatments were carried out at each site: a non-treated control and six different ap - plication timings of Instrata (chlorothalonil, fludioxonil, propiconazole; Syngenta) applied at 9.3 fluid ounces/1,000 square feet (2.96 milliliters/square meter). Treatments No. 2 through 6 were targeted for 8, 6, 4, 2 and 0 weeks before traditional snow cover, respec - tively, and treatment 7 was applied as close to the first significant snowfall of the year as possible. Traditional snow cover timings were established as Nov. 1 for Minocqua, Nov. 15 for Wausau/Wisconsin Rapids, and Dec. 1 for Madison. Dates of actual treatment for each application at the Minocqua site are listed in Table 2. e experimental design was a ran - domized complete block with four replica- tions and individual plots measuring 3 feet × 10 feet (0.9 meter × 3 meters). A number of environmental variables were measured throughout the fall at each site, in - cluding air temperature, relative humidity, dew point and soil temperature at 2 inches (5 centimeters) beneath the surface. In addi - tion, heating degree days (HDD) were calcu- lated for each site, using a base temperature of 50 F. Heating degree days work very much like growing degree days, but the accumula - tion of units occurs when the daily average temperature is below 50 F for the day. For example, on a day when the average of the high and low temperatures is 40 F, the HDD Treatment no. Fungicide Projected application timing † Application dates 2015-2016 2016-2017 2017-2018 1 not treated NA NA NA NA 2 Instrata 9.3 fluid ounces 8 weeks Sept. 1 Sept. 1 Sept. 1 3 6 weeks Sept. 16 Sept. 15 Sept. 14 4 4 weeks Oct. 1 Sept. 30 Sept. 29 5 2 weeks Oct. 13 Oct. 13 Oct. 16 6 0 weeks Nov. 2 Oct. 31 Nov. 1 7 pre-snow Nov. 16 Nov. 17 Nov. 14 † Projected application timing refers to number of weeks before typical snow cover. Typical snow cover was defined as Nov. 1 for Minocqua, Wis., and the pre-snow treatment was put out as close as possible to final snow cover. Table 2. Snow mold fungicide treatment dates at Timber Ridge Golf Club in Minocqua, Wis., in the winters of 2015-2016, 2016-2017, and 2017-2018. Snow mold fungicide treatments at Timber Ridge GC, 2015-2018

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