Management practices, environment, and spray adjuvants influence efficacy and metabolism of bispyribac-sodium in turfgrass.

摘要

Bispyribac-sodium has shown potential for selective annual and roughstalk bluegrass control in cool-season turfgrasses but further research is needed for successful integration in to turf management programs. The objectives of this research were to investigate the influence of management practices, environment, and spray adjuvants on efficacy and metabolism of bispyribac-sodium in turfgrass.;In field experiments, sequential bispyribac-sodium applications controlled annual bluegrass 93% but trinexapac-ethyl did not affect efficacy. Tank mixing trinexapac-ethyl with bispyribac-sodium provided similar annual bluegrass control to the herbicide alone. In field experiments, withholding nitrogen increased annual bluegrass and creeping bentgrass sensitivity to bispyribac-sodium while grasses fertilized biweekly generally had darker color. Weekly nitrogen treatments increased 14C-bispyribac-sodium metabolism in both grasses compared to the unfertilized.;In field experiments, discoloration of creeping bentgrass putting greens was greatest from applications of 37 g/ha every ten days compared to 74, 148, or 298 g/ha applied less frequently. Chelated iron effectively masked discoloration of creeping bentgrass putting greens from bispyribac-sodium while trinexapac-ethyl inconsistently masked these effects. In field experiments, bispyribac-sodium regimes totaling 148, 222, and 296 g/ha controlled annual bluegrass 81, 83, and 91%, respectively, over two years. Pooled over herbicide rates, bispyribac-sodium applied two, three, and six times controlled annual bluegrass 78, 83, and 94%, respectively. Bispyribac-sodium and sulfosulfuron provided substantial reductions (80 to 100%) in roughstalk bluegrass cover in creeping bentgrass fairways by late July but regrowth was detected by October in three years suggesting herbicide applications did not control vegetative stems or crowns.;In growth chamber experiments, annual bluegrass chlorosis and clipping reductions from bispyribac-sodium were exacerbated by increased temperature from 10 to 30° C. Conversely, creeping bentgrass was most sensitive to bispyribac-sodium at 10°C but chlorosis and clipping reductions were less substantial at 20 and 30°. Spray adjuvants increased 14C-bispyribac-sodium foliar absorption by two to threefold in laboratory experiments and improved annual bluegrass control in field experiments by 25 to 50% from treatments with no adjuvants. In metabolism experiments, half life of 14C-bispyribac-sodium in annual bluegrass, creeping bentgrass, and perennial ryegrass was estimated at greater than seven days, one day, and two days, respectively.