Abstract Waterhemp has evolved resistance to seven herbicide modes of action in the United States and five Canada, which limits weed control options for producers. The objective this research was quantify level duration residual multiple herbicide-resistant (MHR) waterhemp with Group 15 herbicides (acetochlor, dimethenamid-p, flufenacet, pyroxasulfone, S -metolachlor) applied preemergence a non...