Mixing in multiple modes of action in any weed control program is imperative. “I am all about redundancy for each application,” says Micheal Owen, weed scientist, Iowa State University. “Each mechanism of action needs to have activity on the target weeds, and preexisting resistances need to be factored in.”

Application timing will take on an even larger role. “Application timing is always a problem because many postemergence herbicide applications are made when weeds are well beyond 2 to 4 in. tall,” Owen says. “If growers are scouting effectively, timing should not be an issue. While weather can impact spray schedules, this can be mitigated by using a soil-applied residual herbicide.”