Wednesday, November 15, 2006 - 9:30 AM

Control of Annual Bluegrass on Putting Greens with Frequent Applications of Bispyribac-sodium.

Travis Teuton1, John C. Sorochan2, Christopher L. Main3, J. Scott McElroy2, and Thomas C. Mueller2. (1) University of Missouri-Columbia, 215 Waters Hall, Columbia, MO 65211, United States of America, (2) University of Tennessee, 2431 Joe Johnson Drive, 252 Ellington Building, Knoxville, TN 37996-4561, (3) Clemson University, 2200 Pocket Road, Florence, SC 29506-9706

Annual bluegrass is one of the most difficult to control weeds in creeping bentgrass putting greens.  Field trials were conducted in 2003 and 2005 to evaluate bispyribac-sodium for annual bluegrass management in 'Penncross' creeping bentgrass greens maintained at a 3 mm mowing height.  Bispyribac-sodium applied weekly at 12 or 24 g ai/ha controlled annual bluegrass 86% 12 wk after initial treatment (WAIT).  In 2003, bispyribac-sodium applied at 12 and 24 g ai/ha/wk injured creeping bentgrass approximately 15 to 50% by 4 WAIT, respectively.  However, injury was transient and was not evident by 12 WAIT.  In 2005, the 12 and 24 g ai/ha/wk injured creeping bentgrass 15 to 85% by 8 WAIT, respectively and was still evident throughout the trial.  Putting green quality was reduced when compared to untreated creeping bentgrass by the same treatments.  The removal of annual bluegrass caused soil exposure until creeping bentgrass grew over the bare areas contributing to decreased quality evaluations.  Management of annual bluegrass in creeping bentgrass putting greens is possible with bispyribac-sodium at 12 g ai/ha/wk applied for 12 weeks. Complete annual bluegrass control may take several years and creeping bentgrass injury may occur when mowed at 3mm.