While the list of herbicide-resistant weeds continues to grow, weed scientists are focused on the “driver weeds” that can potentially cause the most economic damage — Palmer amaranth, waterhemp and marestail (also known as horseweed).

“While we have concerns regarding the evolution of resistance in several weed species, these are the weeds of major concern moving forward over the next five years as the infestation levels intensify and expand,” says Bryan Young, weed scientist at Southern Illinois University.

“We need to improve the control of these weeds, learn how to recognize failure due to glyphosate resistance, and take a proactive approach to deter the shift towards resistance in areas that would still be feasible,” he adds. “If you wait, and react to weed resistance to glyphosate on your farm, you are too late.”

Growers need a playbook of strategies to fight the encroachment of weed resistance. Here are some key plays growers can use to start the offense.