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 Injury from single glyphosate applications Treatment Rate Herbicide Fluid ounces/acre Pound ae/acre Roundup Pro Max (glyphosate) 3.56 0.13 66BCDE 18C 15E 7.1 0.25 94ABC 33B 34D 14.2 Application % annual bluegrass control in April 0.50 85ABCD 46B 63C December % Replay perennial ryegrass injury 3 WAIT 6 WAIT 28.4 1.0 41E 62A 92A 3.56 0.13 63CDE 0D 3FG 7.1 91ABC 4D 23DE 0.50 99A 12CD 54C 28.4 1.0 100A 13CD 76B 3.56 0.13 56DE 0D 0G 7.1 0.25 48E 7C 0G 14.2 0.50 73ABCDE 18CD 0G 28.4 February 0.25 14.2 January 1.0 98AB 38B 0G 73ABCDE 12CD 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 1. Annual bluegrass control and perennial ryegrass injury resulting from single glyphosate applications. greater than 0.13 pound ae/acre should be avoided if the temperature is below 50 F. Using glyphosate in overseeded bermudagrass Since JS501 and Replay must be mature before their glyphosate tolerance is sufcient for weed control without injury, it is not known whether these cultivars can be used for overseeding in bermudagrass. In overseeded bermudagrass, there are three competing interests: perennial ryegrass must be well developed to tolerate glyphosate, bermudagrass must be completely dormant so as not to be injured, and annual bluegrass must be young enough to be controlled with glyphosate. Research was recently conducted at Auburn University to determine the optimal timing and rate of glyphosate application in bermudagrass overseeded with Replay perennial ryegrass for annual bluegrass control. Materials and methods Replay (Jacklin Seed) was overseeded into bermudagrass in mid-October in 2010 and 2011 at 800 pounds seed/acre (896.68 kilograms/hectare). Roundup ProMax (glyphosate, Monsanto) was applied the frst week of December, January and February for both overseedings. Two application regimes were tested: a single Roundup ProMax application and two sequential applications, with the sequential application made three weeks after the initial application. At each application timing, single applications of Roundup ProMax were made at rates of 0 (nontreated), 3.56, 7.1, 14.2 and 28.4 fuid ounces/acre (0, 0.26, 0.51, 1.03 and 2.07 liters/hectare) (Table 1). Sequential applications were 3.56 followed by 3.56 fuid ounces/acre, 7.1 followed by 7.1 fuid ounces/acre, 14.2 followed by 14.2 fuid ounces/acre, and 28.4 followed by 28.4 fuid ounces/acre (Table 2). A comparison treatment of Prograss (ethofumesate, Bayer Environmental Science) was applied twice at 86 fuid ounces/acre (6.28 liters/ hectare or 1.0 pound ai/acre) the frst week of December followed by the same amount in the third week of December. Tis treatment has resulted in greater than 90% annual bluegrass control in previous research (5). Results Data from Roundup ProMax and Prograss treatments were collected for perennial ryegrass injury and annual bluegrass control. Injury was October 2013 GCM 91

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