Studies were conducted during 2003 and 2004 to evaluate selected herbicides for annual bluegrass (Poa annua L.) control in hybrid bermudagrass (Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt-Davey) overseeded with perennial ryegrass (Lolium perenne L.). Herbicides were applied prior to overseeding during October in an area naturally infested with annual bluegrass. Perennial ryegrass was seeded at 400 kg ha-1. Rimsulfuron applied at 17.5 to 35 g a.i. ha-1 14 days prior to overseeding provided 80 to 90% annual bluegrass control 20 wk afer application with minimal injury to the perennial ryegrass overseed. In a second study where several herbicides were compared, rimsulfuron (35 g ha-1), flazasulfuron (52 g ha-1), sulfosulfuron (105 g ha-1) and trifloxysulfuron (17.5 g ha-1) provided 75 to 85% annual bluegrass control 20 wk after application while foramsulfuron (28.5 g ha-1) provided less than 65% control. By 25 wk after treatment, annual bluegrass control with all treatments declined to less than 75%. In a third study, bispyribac applied postemergence (75 g ha-1) at first annual bluegrass bloom provided 75 to 85% control 4 to 6 wk after treatment. By 8 to 10 wk after treatment, control declined to less than 70%. Sequential application of bispyribac improved late-season annual bluegrass control.
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