Bispyribac-sodium Metabolism in Annual Bluegrass, Creeping Bentgrass, and Perennial Ryegrass.

Bispyribac-sodium selectively controls annual bluegrass (Poa annua L.) in creeping bentgrass (Agrostis stolonifera L.) and perennial ryegrass (Lolium perenne L.) which may be attributed to differential metabolism among species.  To test this hypothesis, laboratory experiments investigated metabolism of ¹⁴C-bispyribac-sodium in annual bluegrass, creeping bentgrass, and perennial ryegrass.  Creeping bentgrass and perennial ryegrass metabolized ¹⁴C-bispyribac-sodium by approximately 50% after one day while annual bluegrass metabolized less than 20%.  After seven days, parent herbicide recovered in annual bluegrass, creeping bentgrass, and perennial ryegrass was 73, 32, and 39% of total radioactivity per species, respectively.  Polar metabolites recovered after seven days in annual bluegrass, creeping bentgrass, and perennial ryegrass were 24, 59, and 55% of total radioactivity per species, respectively.  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.  Results support the hypothesis that differential tolerances of these grasses are attributed to herbicide metabolism.