Annual Bluegrass Control in Seedling Creeping Bentgrass with Bispyribac-sodium

Golf course fairways may be renovated to replace different species or older cultivars of creeping bentgrass (Agrostis stolonifera L.) (CBG) with improved bentgrass cultivars. Older cultivars are often infested with annual bluegrass (Poa annua L.) (ABG), and a primary goal of the renovation is to remove ABG from the turf. A series of trials were conducted from 2004 to 2007 to determine optimum bispyribac-sodium (BPS) application regimes to control ABG without excessive injury to establishing CBG. Bispyribac-sodium applications were initiated as soon as one week after CBG seedling emergence and continued at various rates and timings up to seven weeks after seedling emergence. Bispyribac-sodium treatments generally caused CBG seedling injury that was manifested as a reduction in growth and color. All treatment regimes provided significant reductions in ABG populations in some years. Several treatment regimes provided outstanding ABG control in all years. When balancing ABG control with CBG injury, applying 74 g ai/ha at 3 and 5 weeks after seedling emergence (WAE) gave excellent ABG control with moderate, but temporary, CBG injury. Applying 74 g only at 3 WAE provided moderate ABG control and minimal CBG injury with minimized application labor.