Submitted to: California Alfalfa Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/24/2008
Publication Date: 12/3/2008
Citation: Boydston, R.A. 2008. Weed management research in alfalfa seed production in Washington state. 2008 Calif. Alfalfa and Forage Symposium and Western Seed Conference, San Diego, CA UC Cooperative Extension, Plant Sciences Department, University of California, Davis, CA 95616. On CD and http://alfalfa.ucdavis.edu.
Technical Abstract: Weed control is an important component of producing high quality and high yielding alfalfa seed. Alfalfa seed is produced with wider row and lower plant populations than alfalfa forage requiring greater weed management inputs. Flumioxazin was evaluated for weed control in alfalfa seed and forage production in 2007 and 2008. February dormant applications of flumioxazin at 0.125 and 0.25 lb ai/a plus paraquat to alfalfa planted the previous fall inhibited early growth and forage yields of the first cutting of alfalfa in 1 of 2 years. Alfalfa forage yield of the second cutting was not reduced by flumioxazin. Established alfalfa treated with flumioxazin at 0.125 lb ai/a in February produced seed yields similar to treating with other currently registered preemergence herbicides or paraquat alone. Forage yield of established alfalfa treated with flumioxazin at 0.125 lb ai/a in February was similar to that treated with currently registered herbicides. Alfalfa exhibited good tolerance to asulam at 3.3 lb ai/a in forage and seed production trials in 2007 and 2008. Carfentrazone exhibited potential for use as a ‘set back’ herbicide for alfalfa seed production.