Golf Course Management

APR 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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84 GOLF COURSE MANAGEMENT 04.19 an affordable option, whereas Velista (pen- thiopyrad, Syngenta) was used to represent a more expensive but more effective treatment. ese fungicide applications were made at the high label rate and immediately followed by 1 ⁄8 inch (3.2 millimeters) of irrigation, with an- other 1 ⁄8 inch of irrigation at night. ese lo- cations were evaluated via aerial mapping the following spring for the treatments' impact on spring dead spot suppression. Treatments included: • Untreated • Tebuconazole 3.6F at 0.9 fluid ounce/ 1,000 square feet across the entire plot (blanket) (1.23 kilograms ai/hectare) • Velista at 0.7 wt. ounce/1,000 square feet across the entire plot (blanket) (2.13 ki- lograms ai/hectare) • Site-specific Velista at 0.7 wt. ounce/ 1,000 square feet based on disease his- tory (2.13 kilograms ai/hectare) Spring dead spot incidence was reported as patch count, representing the number of spring dead spot incidence centers per plot, and as diseased area/plot (square millimeters of disease within every square meter of turf or square millimeters/square meter) representing the area impacted by spring dead spot com - pared with the entire plot. Statistical analysis indicated the results for both years was signif - icantly different, so data were separated and analyzed by each year. Results and discussion Our methods in 2016 resulted in a 51% reduction of fungicides used in site-specific treatments when compared with the blanket treatments. Improved automation and appli - cation techniques resulted in a 65% reduction of fungicides in 2017. Treatment differences were observed in both years when plots were analyzed for both patch count (Table 1) and diseased area (Table 2). e results reported in 2017 represent the treatments made in 2016, and results reported in 2018 represent treatments made in 2017. Overall, tebuconazole remains consistently inconsistent, as it did not outperform the untreated plots for any metric besides patch count in 2018. Blanket applications of Ve - lista were superior to site-specific applications when analyzed for patch count. is may be a result of new spring dead spot incidence, not accounted for in previous years. Site-specific applications of Velista were statistically supe - rior to tebuconazole and equivalent to blanket SDS patch counts per plot Mean area of plot impacted by spring dead spot Price list for hard goods associated with SDS management Treatments Patch count, 2017 † Patch count, 2018 Untreated 9.51 A 15.71 A Tebuconazole 3.6F, blanket application 7.85 A 11.46 B Velista, blanket application 1.89 C 4.93 C Velista, site-specific application 4.46 B 9.00 B LSD (0.05) 2.05 2.55 † Values within a column that are followed by the same letter are not significantly different from one another. Table 1. Mean spring dead spot incidence centers (patch counts) per plot arranged by treatment. Treatments Diseased area (square millimeters/square meter) 2017 † 2018 Untreated 11,399 A 9,834 A Tebuconazole 3.6F, blanket application 9,991 A 8,709 A Velista, blanket application 2,351 B 3,662 B Velista, site-specific application 4,475 B 4,997 B LSD (0.05) 3,397 2,803 † Values within a column that are followed by the same letter are not significantly different from one another. Table 2. Mean area of plot impacted by spring dead spot. SDS suppression program Area treated Product Cost Blanket Velista applications 50 acres two fall applications at 0.7 wt. oz./ 1,000 square feet $25,382.00 GPS-guided, site-specific Velista applications 17.5 acres two fall applications at 0.7 wt. oz./ 1,000 square feet $8,883.70 Contracted service: SDS incidence maps and spray maps 50 acres individual hole maps with spring symptoms $3,920.00 † Sprayer upgrade: GPS-guided, RTK-corrected spray system n/a difference in cost of GPS unit vs. no GPS $35,000.00 ‡ † Price estimate: RVA Drone Co., 2018. ‡ Price estimate: Smith Turf and Irrigation. GeoLink: GPS/individual nozzle control to Toro 5800 sprayer, 2018. Table 3. Price list for hard goods associated with site-specific management vs. blanket management of spring dead spot.

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