Experiments in 2022 and 2023 at multiple locations in North Carolina aimed to identify alternative herbicide combinations that could provide effective preplant foliar weed control when glyphosate is unavailable. All combinations containing rimsulfuron + thifensulfuron provided 95% to 98% control of henbit, which is 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 against purple cudweed, providing control that was comparable to that of glyphosate (≥97%). Tiafenacil applied alone provided limited control of most of the weed species evaluated, but showed compatibility in mixtures, suggesting it has 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.

Henbit is a winter annual weed that is not effectively controlled by spring-applied herbicide applications. Research was conducted to determine henbit’s emergence pattern and whether fall-applied residual herbicides would be effective for henbit control in the spring. Henbit emerges in Louisiana from late October through March, but emergence predominantly occurs in the last week of October through the first week of December. Applying paraquat plus flumioxazin, oxyfluorfen, or rimsulfuron:thifensulfuron November 1 through December 15 provided better than 90% henbit control in March. Applying paraquat plus S-metolachlor on November 15 or December 1 provided 92% henbit control, which was similar to flumioxazin, oxyfluorfen, and rimsulfuron:thifensulfuron. The addition of flumioxazin, oxyfluorfen, or rimsulfuron:thifensulfuron to paraquat reduced the height of henbit plants by 4% to 22% of nontreated plants when applied November 1 through December 15. These studies indicate that crop producers can achieve control of henbit in March following November 1 through December 15 applications of paraquat plus flumioxazin or rimsulfuron:thifensulfuron; however, paraquat plus oxyfluorfen can be applied October 15 through December 15 to achieve similar control.