Evaluation of amicarbazone behavior, selectivity, and utilization in turfgrass
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Amicarbazone is a photosystem ΙΙ inhibitor with potential for controlling annual bluegrass (Poa annua L.) in turfgrasses. Comprehensive investigations are required to evaluate application rates, regimens, timings, and mechanisms of selectivity to help maximize efficacy of this herbicide in turfgrass. Amicarbazone selectivity for annual bluegrass control in cool-season turfgrasses could be attributed to differential levels of absorption, translocation, and metabolism. Annual bluegrass showed more absorption and translocation but less metabolism of amicarbazone compared to creeping bentgrass (Agrostis stolonifera L.) and tall fescue (Festuca arundinaceae Shreb.). Results of greenhouse experiments indicated that temperature has greater phytotoxic effect on turfgrass injury and shoot biomass reductions of annual bluegrass and tall fescue than bermudagrass following amicarbazone applications. Increased tall fescue injury from summer amicarbazone applications are likely attributed to effects of temperature on herbicide phytotoxicity. Foliar amicarbazone uptake in bermudagrass was comparable to tall fescue but less than annual bluegrass at low temperatures (25/20 ºC). Foliar and root uptake in annual bluegrass, bermudagrass, and tall fescue increased as temperature increased but uptake in bermudagrass was less than annual bluegrass and tall fescue at high temperatures (40/35 ºC). Moreover, practitioners may safely use amicarbazone in seashore paspalum in winter, spring, and summer at labeled use rates but summer applications may inhibit shoot growth for up to 4 weeks.