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Plant Growth Regulator Regimens Reduce Poa annua Populations in Creeping Bentgrass

McCullough, Patrick E., Hart, Stephen E., Lycan, Darren W.
Applied turfgrass science 2005 v.2 no.1 pp. 0
plant growth, Poa annua, weeds, Agrostis stolonifera var. palustris, weed control, paclobutrazol, plant growth substances, application timing, application rate, turf grasses, turf management, lawns and turf, New Jersey
Plant growth regulators (PGRs) are commonly applied for annual bluegrass (L.) suppression but various PGR regimens may be more applicable in creeping bentgrass (Huds.) management than exclusive applications. Two field experiments in Riverton, NJ investigated various regimens of paclobutrazol ((⁺/-)-(R*,R*)-b-[(4-chlorophenyl) methyl]-a-(1, 1-dimethyl)-1H-1,2,4,-triazole-1-ethanol) (PB) and trinexapac-ethyl ([4-(cyclopropyl-[a]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester]) (TE) for control in creeping bentgrass golf course fairways. Over four years, coverage was greater in the spring compared to summer and fall. In the first experiment, reductions from initial populations were 22 and 30% in untreated turf and turf treated only with TE, respectively. Reductions in were ≈ 55% for turf receiving PB with and without TE applications. In the second experiment, PB reduced populations to approximately half those of the untreated plots but combinations with TE did not enhance turf quality or suppression. Routinely applying PB at 0.14 kg/ha every 3 weeks provided similar control to single applications of 0.56 kg/ha while both regimens gave better control than PB at 0.28 kg/ha applied in the spring and fall. Overall, PB will be an effective tool for suppressing in creeping bentgrass fairways for northeastern golf courses; however, tank mixing TE with PB will likely not enhance these effects.