Tuesday, November 14, 2006

Kentucky Bluegrass Cultivar Sensitivity to Bispyribac-sodium.

John Stier1, Richard Borland2, Jacob L. Schneider1, Andrew Hollman3, and Kevin Morris4. (1) University of Wisconsin, Univ. of WI-Horticulture Dept., 1575 Linden Dr., Madison, WI 53706-1590, (2) Becker Holding Group, 3503 Peterson Road, Fort Pierce, FL 34947-6334, (3) U of MN Hort, Rm. 305 Alder Hall, 1970 Folwell Ave., 1970 Folwell Ave., St. Paul, MN 55108, United States of America, (4) National Trufgrass Federation, Inc., BARC-West, Circle Dr.Bldg. 003 Rm. 217, Beltsville, MD 20705

Annual bluegrass (AB; Poa annua L.) occurs as a hard-to-control weed in Kentucky bluegrass (KBG; Poa pratensis L.) golf course fairway and sod turf.  Bispyribac-sodium has recently been labeled for control of AB in creeping bentgrass and perennial ryegrass turf.  Data are needed on sensitivity of KBG.  Kentucky bluegrass cultivars in the 2000 NTEP test were maintained as either fairway or lawn turf.  The experimental design was a strip-plot, randomized block with three replications.  Bispyribac-sodium was applied to one-half of each plot in two sequential applications, at a 14 d interval, during June 2005.  Phytotoxicity was evaluated 3, 7, 14, 21, 28, and 56 days after treatment.  Phytotoxicity to KBG cultivars ranged from none to nearly complete kill, with most cultivars suffering minimal to moderate but short-term phytotoxicity.  Some cultivars which showed moderate to high sensitivity eventually recovered but with darker green, stunted leaves, similar to growth resulting from plant growth regulators.  The data are important because AB contamination appears to be increasing in sod production fields, lowering the quality and marketability of KBG sod.  AB is a perennial problem in many KBG fairways, detracting from the utility of the golf course and increasing irrigation and chemical inputs needed to maintain grass survival.  A large number of KBG varieties have sufficient tolerance to bispyribac-sodium to justify its use for AB removal at both fairway and lawn (sod) mowing heights.