RESPONSE OF QUACKGRASS (ELYTRIGIA-REPENS) BIOTYPES TO PRIMISULFURON

Quackgrass biotypes collected from 15 locations exhibited differential response to primisulfuron at 20 g ha-1 in field experiments at Hudson , NY during 1990 and 1991. Quackgrass control ranged from 23 to 100% 7 7 days after application (DAA) in 1990 and from 38 to 100% 88 DAA in 1 991. The biotype from Montpelier, OH was the most tolerant both years. Differential response of quackgrass biotypes from five locations was confirmed in greenhouse experiments. The primisulfuron rate required t o reduce shoot regrowth by 50% in the greenhouse was estimated at 15, 15, 17, 17, and 37 g ha-1 for biotypes from Amherst, MA; Mahnomen MN; Fargo, ND; State College, PA; and Montpelier, OH, respectively. Quackg rass shoot regrowth was reduced more when primisulfuron was applied wi th the linear alcohol ethoxylate additive 1412-70 compared with Scoil, Sylgard 309, Agridex, or X-77.