Annual Bluegrass Control in Perennial Ryegrass and Tall Fescue with Bispyribac-sodium Stephen E. Hart and Patrick E. McCullough Rutgers, The State University of New Jersey Introduction Annual bluegrass is a problematic weed in cool-season turfgrass that reduces aesthetics and functionality. Annual bluegrass has poor heat, drought, and stress tolerances, and thus, requires more water, fungicides, and intensive management for long-term turf culture. Bispyribac-sodium was recently registered for use in creeping bentgrass and perennial ryegrass fairways for selective annual bluegrass control. However, comprehensive research is warranted for annual bluegrass control and response of tall fescue and perennial ryegrass to multiple applications of bispyribac-sodium. Results and Discussion Turfgrass Injury In 2006, bispyribac-sodium caused some chlorosis to tall fescue and perennial ryegrass, however injury did not exceed 20% (Figures 1 and 2). The highest levels of chlorosis were observed 10 days following the sequential application of bispyribac-sodium at 222 and 296 g/ha (Picture 1). In 2007, tall fescue and perennial ryegrass injury did not exceed 5% at any evaluation time. Fine fescue was not injured by bispyribac-sodium (not shown). Annual Bluegrass Control All bispyribac-sodium treatments provide substantial control of annual bluegrass but rates exceeding 74 g/ha were required to obtain nearly complete control, especially in perennial ryegrass (Figure 3). By six WAIT, annual blue grass control was only 24, 65, and 78% in tall fescue when bispyribac-sodium was applied at 74, 148, and 222 g/ha, respectively. Bispyribac-sodium at 296 g/ha provided nearly complete annual bluegrass control. Control levels in perennial ryegrass were generally greater than in tall fescue but rates above 74 g/ha were required to achieve 80% or greater control. Figure 1. Perennial ryegrass injury three week after initial bispyribac-sodium treatments in perennial ryegrass, 2006-2007, Adelphia, NJ. 2006 2007 Figure 2. Tall fescue injury three and six weeks after initial bispyribac-sodium treatments in tall fescue, 2006, Adelphia, NJ. 3 WAIT 6 WAIT Objective To investigate bispyribac-sodium efficacy for annual bluegrass control in tall fescue and perennial ryegrass. Materials and Methods Field studies were conducted in the summer of 2006 and 2007 to evaluate the response of tall fescue ‘Avenger’, and perennial ryegrass ‘Gator 3’ to bispyribac-sodium herbicide. Annual bluegrass control was also evaluated. In 2007 fine fescue ‘Ambassodor’ was also included. Sequential applications of bispyribac-sodium were applied at rates ranging from 37 g ai/ha to 296 g/ha at approximately a three week interval. Experiments were initiated on May 30 and May 31 in 2006 and 2007, respectively. All treatments were applied using a single nozzle CO2 pressured sprayer calibrated to deliver a total of 375 L ha-1. Nozzles used were 9504E and CO2 regulators were set for 220 kPa. Experimental design was a randomized complete block with four replications of 1 x 3-m plots. Turfgrass chlorosis was rated on a percent scale where 0 equaled no chlorosis and 100 equaled complete desiccation. Annual bluegrass cover was evaluated prior to herbicide application and 10 weeks after initial treatment (WAIT). Figure 3. Annual bluegrass control from sequential applications of bispyribac-sodium in perennial ryegrass, 2006-2007, Adelphia, NJ. Conclusions Bispyribac-sodium has potential to control annual bluegrass in tall fescue and perennial ryegrass without significant injury. 2006 Picture 1. Perennial ryegrass injury three week after initial bispyribac-sodium treatments in perennial ryegrass, 2007, Adelphia, NJ. Check 120 G A/A 2007