In many cases there may be a need for overlapping residuals. Valent’s Refsell says, “For example, one program may be a preplant burndown application to remove winter annuals, followed by a preemergence application to provide residual control of resistant weeds such as Palmer amaranth and waterhemp.”

Even tillage may be necessary to effectively manage early-season weeds. “I suspect some may opt for tillage or herbicides, while some situations may necessitate both be used,” Hager says. “Whatever control program is used, it is imperative that all existing vegetation be controlled before any crop seeds are planted, and preferably before any of the winter annual weed species produce viable seeds.”