Response of creeping bentgrass, annual bluegrass, and Kentucky bluegrass to foliar, soil, or foliar plus soil applications of bispyribac-sodium was evaluated in greenhouse studies. Soil-alone and foliar plus soil applications of bispyribac-sodium at 148 or 296 g ai/ha resulted in greater injury and shoot dry weight reduction of all species 28 d after treatment (DAT) compared to foliar-alone treatments. Creeping bentgrass was less injured than annual or Kentucky bluegrass regardless of application placement. Further studies evaluated foliar and root absorption and translocation of 14C-bispyribac-sodium in creeping bentgrass, annual bluegrass, Kentucky bluegrass, and roughtstalk bluegrass. Foliar absorption into creeping bentgrass was less than that of other species at most harvest timings from 4 to 72 h after treatment. Annual and roughstalk bluegrass translocated greater amounts of foliar-absorbed 14C to the crown and shoots compared to creeping bentgrass. Annual and roughstalk bluegrass accumulated approximately 47% more 14C per dry weight of plant tissue than creeping bentgrass and 74% more than Kentucky bluegrass after 72 h in nutrient solution containing 14C-bispyribac-sodium. Annual and roughstalk bluegrass translocated approximately 80% of root-absorbed 14C to shoots, whereas creeping bentgrass and Kentucky bluegrass translocated slightly less (66% of absorbed for both species). These studies suggest that bispyribac-sodium is readily absorbed by roots and translocated to shoots which may contribute to its total activity within a plant. In addition, creeping bentgrass displayed lower amounts of foliar and root absorption and subsequent translocation than annual and roughstalk bluegrass which may contribute to greater bispyribac-sodium tolerance displayed by creeping bentgrass.

Greenhouse and laboratory experiments were conducted to investigate the response of common lambsquarters to POST applications of halosulfuron–methyl plus 2,4-D admixtures and to investigate the effects of 2,4-D on the absorption, translocation, and metabolism of halosulfuron. In the greenhouse, halosulfuron at 0, 4.5, 9, 18, and 36 g ai/ha was applied alone and mixed with 2,4-D at 0, 17, 35, and 70 g ai/ha POST to 7.5- to 9-cm seedlings, and plant fresh weights were determined 4 wk after treatment (WAT). Halosulfuron alone did not control this weed, while fresh weights of common lambsquarters treated with 2,4-D declined hyperbolically as rates increased. A synergistic response for mixtures of these herbicides occurred, as observed fresh weights for all combinations were less than expected based on independent action and the calibrated marginal responses. In the laboratory, 7.5- to 9-cm seedlings were treated POST with commercially formulated halosulfuron at 9 and 18 g/ha and 2,4-D at 0, 70, and 140 g/ha, respectively, followed by foliar-applied 14C-halosulfuron. Absorption of 14C-halosulfuron increased with time, and absorption and translocation were not influenced by the addition of 2,4-D. Results from these studies inferred that halosulfuron and 2,4-D were generally synergistic on common lambsquarters and that mechanisms other than absorption, translocation, and metabolism may explain this response.