Golf Course Management

JUL 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 Bermudagrass exhibited the least amount of recovery from spring dead spot at 14 weeks after treatment in response to Specticle applied at 0.031 pound/acre. of Tifway bermudagrass was observed in response to applications of Surfan (1.49 pounds/acre [1.68 kilograms/hectare]) (0% regrowth) and Barricade (0.936 pound/acre [1.05 kilograms/hectare]) (3% regrowth) compared to a non-treated check (18%) at six weeks after initial treatment. Specticle. Bermudagrass exhibited the least amount of recovery (13% to 14%) from spring dead spot at 14 weeks after treatment in response to Specticle at 0.031 pound/acre (0.035 kilogram/ hectare). Specticle is an alkylazine herbicide that controls susceptible grass and broadleaf weeds through the inhibition of cellulose biosynthesis (3). Although Specticle offers turfgrass managers an alternative mode of action for the control of key turfgrass weeds (3,11), long soil residual activity (>150 days) may limit bermudagrass recovery from stress. Researchers (11) have reported that perennial ryegrass cover in plots treated with Specticle at 0.047 pound/acre (0.053 kilogram/hectare) and 0.062 pound/acre (0.070 kilogram/hectare) measured 37% to 48% compared to 88% for a non-treated check 257 days after initial treatment. Reduced recovery in response to Specticle may be explained by other research (12), where hybrid bermudagrass injury on sand-based systems was 25% to 47% at six weeks after treatment in response to Specticle at 0.031 pound/ acre (0.035 kilogram/hectare), while reductions in root length density (>58%) were observed on root systems 2 to 6 inches (5 to 15 centimeters) in 84 GCM July 2013 depth following applications of Specticle at 0.031 to 0.062 pound/acre (12). Still other researchers (39) investigated Riviera common bermudagrass root strength in response to sequential applications of Specticle (0.031 or 0.046 pound/acre [0.035 or 0.052 kilogram/ hectare)], Specticle followed by Ronstar (1.99 pounds/acre [2.24 kilograms/hectare]) or Barricade (0.749 pound/acre [0.84 kilogram/hectare]), and Barricade (0.749 pound/acre [0.84 kilogram/ hectare]). No differences in loose stolon number and root strength were observed between the nontreated check and Specticle treatments at 16 weeks after initial treatment; however, bermudagrass root strength was signifcantly lower in response to sequential Barricade treatments at 16 weeks after initial treatment (17). However, this research examined the response of four-year-old rooted bermudagrass to Specticle applications, whereas our research examined the ability of bermudagrass stolons to encroach from surrounding plants and root in Specticle-treated soil. Differential responses in spring dead spot bermudagrass recovery from year to year may be attributed to the severe drought conditions experienced in Texas during 2011. The Palmer drought severity index (PDSI) was -4.19 for April and -5.08 for May in Texas during 2011, indicating the most severe drought since 1895 (6). Although research plots were irrigated, high temperatures and low humidity during spring and summer may have increased evaporative demand, thus reducing

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