Alternatives to Glyphosate for Spring Preplant Foliar Weed Management

Abstract An experiment was conducted in 2022 and 2023 at multiple locations in North Carolina to identify alternative herbicide combinations capable of providing effective preplant foliar weed control when glyphosate is unavailable. All combinations containing rimsulfuron + thifensulfuron provided 95% to 98% control of henbit, comparable to all glyphosate-based combinations. Treatments containing glyphosate achieved 100% control of common chickweed, and rimsulfuron + thifensulfuron combined with clethodim (90%) or 2,4-D (89%) were the only treatments that provided comparable control. Paraquat effectively controlled henbit and common chickweed, providing 91% and 87% control of these species, respectively. Although no treatment controlled annual bluegrass as effectively as glyphosate-based mixtures, paraquat alone, paraquat + 2,4-D, and clethodim + rimsulfuron + thifensulfuron each achieved ≥ 88% control. Saflufenacil was highly efficacious on purple cudweed, providing control comparable to glyphosate (≥ 97%). Tiafenacil alone provided limited control of most of the weed species evaluated in this study, but showed compatibility in mixtures, suggesting utility within diversified preplant foliar herbicide programs targeting specific weeds. While glyphosate remains available for use, incorporating one or more of these herbicides could enhance control of glyphosate-resistant weed biotypes and reduce selection pressure on glyphosate-susceptible weeds. Overall, rimsulfuron + thifensulfuron, paraquat, saflufenacil, tiafenacil, and clethodim, applied alone or in combination, offer practical preplant foliar options that can strengthen existing glyphosate-based programs and sustain effective winter annual weed control should glyphosate become limited or unavailable.