Golf Course Management

OCT 2013

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

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research Sequential glyphosate applications Treatment Rate Herbicide Fluid ounces/acre Pound ae/acre % annual bluegrass control in April Roundup Pro Max (glyphosate) 3.56 fb 3.56 0.13 fb 0.13 7.1 fb 7.1 14.2 fb 14.2 Application December % Replay perennial ryegrass injury 3 WAIT 6 WAIT 100A 28CD 43D 0.25 fb 0.25 97AB 34C 61C 0.50 fb 0.50 58D 55B 84AB 28.4 fb 28.4 25E 70A 98A 0.13 fb 0.13 94AB 0F 23E 7.1 fb 7.1 0.25 fb 0.25 100A 2F 43D 14.2 fb 14.2 0.50 fb 0.50 100A 9EF 77B 28.4 fb 28.4 January 1.0 fb 1.0 3.56 fb 3.56 1.0 fb 1.0 95AB 17DE 95A 3.56 fb 3.56 67CD 2F 0F 0.25 fb 0.25 84ABC 8EF 0F 14.2 fb 14.2 0.50 fb 0.50 98AB 31C 0F 28.4 fb 28.4 February 0.13 fb 0.13 7.1 fb 7.1 1.0 fb 1.0 84ABC 39C 12EF 73BCD 12EF 14EF Additional treatment December Prograss (ethofumesate) 86 fb 86 Note. Data were pooled across 2010-2011 and 2011-2012 seasons. Means sharing a letter within a column are similar according to statistical analysis. Abbreviations: WAIT, weeks after initial treatment; fb, followed by. Table 2. Annual bluegrass control and perennial ryegrass injury resulting from sequential glyphosate applications. ally on a scale of 0% to 100%, where 0% corresponds to no control and 100% to complete control. Annual bluegrass was evaluated in April in order to determine the level of season-long control. December applications Results indicated that December applications of Roundup ProMax were too injurious to the perennial ryegrass. Single applications greater than 3.56 fuid ounces/acre resulted in 30% or greater injury three and six weeks after initial treatment. Similarly, all sequential glyphosate applications resulted in greater than 40% injury six weeks after initial treatment. Annual bluegrass control was generally poor from the December application timing because annual bluegrass germinated after applications were made. This overview of the second year of the study (taken Feb. 21, 2012) shows differences in perennial ryegrass injury and annual bluegrass control from different treatments and application timings. 92 GCM October 2013 evaluated visually on a scale of 0% to 100%, where 0% corresponds to no injury, 100% to complete death and 20% to the maximum commercially acceptable level of injury. Injury was evaluated three and six weeks after initial treatment, when maximum glyphosate injury would be expected. Annual bluegrass control was also evaluated visu- January applications Te January application timing was much better for both perennial ryegrass safety and annual bluegrass control. Single glyphosate applications at 7.1 fuid ounces/acre or greater resulted in greater than 90% annual bluegrass control. However, rates greater than 7.1 fuid ounces/acre resulted in greater than 50% injury at six weeks

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