HERBICIDE COMPARISONS ON QUACKGRASS (ELYTRIGIA-REPENS) WITHIN DIFFERENT CROP COMPETITION AND TILLAGE CONDITIONS

Five herbicides (cloproxydim, fluazifop, haloxyfop, quizalofop, and se thoxydim) were compared from 1984 to 1988 at 250 and 400 g ha-1 for co ntrolling quackgrass within different crop competition and tillage con ditions at the Lacombe Research Station. Crop competition usually augm ented quackgrass control with the herbicides in conventional-tillage p lots although direct statistical comparisons were not made. Without cr op competition, haloxyfop and quizalofop at 250 g ha-1 were more effec tive than the other herbicides in conventional tillage 1 mo after trea tment (MAT). In a conventional-tillage situation on a unit active ingr edient basis, the herbicides ranked in order of decreasing activity as follows: quizalofop greater-than-or-equal-to haloxyfop > fluazifop > cloproxydim > sethoxydim. In a zero-tillage situation, none of the her bicides reduced quackgrass shoot weights by 50% 3 MAT. However, haloxy fop and quizalofop were more effective in suppressing quackgrass shoot weight than the other herbicides in the zero-tillage experiments 3 MA T.