Short-term split application effects of grass-specific herbicides on quackgrass (Elytrigia repens) under field conditions

Field experiments were conducted at the Lacombe Research Station from 1989 to 1991 to determine if short-term, split applications of grass-specific herbicides would improve quackgrass control relative to single applications. Quackgrass infested plots were planted to canola the first year and barley the following year. Glyphosate applied at 880 g/ha controlled quackgrass to a greater extent and for a longer time period than any of the grass-specific herbicides. In contrast to glyphosate, none of the grass-specific herbicides controlled quackgrass 1 yr after treatment. Quackgrass control with sethoxydim or fluazifop-P was usually similar when applied as single or short-term, split applications. In contrast, quizalofop often provided better quackgrass control and higher crop yields when short-term, split applications were compared to a single application with the same total amount of quizalofop. However, the extent of increased quackgrass control is difficult to justify due to increased application costs and inconvenience.