Florpyrauxifen‐Benzyl Controls <i>Cirsium arvense</i> by Inhibiting Root Growth and Decreasing Root Bud Regeneration

ABSTRACT Cirsium arvense L. (Canada thistle) is a perennial weed with an extensive root system and prolific vegetative propagation through adventitious root buds, making long‐term management challenging. Florpyrauxifen‐benzyl, a novel synthetic auxin herbicide, has shown potential for controlling broadleaf weeds, but its effects on C. arvense root growth and regeneration are not documented. Greenhouse studies evaluated florpyrauxifen‐benzyl at 9–38 g ai ha −1 , applied as single or sequential treatments at the rosette and bolting stages, measuring control, root biomass reduction, and root bud regeneration. A second greenhouse study compared florpyrauxifen‐benzyl (29 g ha −1 ) with glyphosate, clopyralid, 2,4‐D, glufosinate, flazasulfuron, carfentrazone, and selected mixtures. Field studies evaluated florpyrauxifen‐benzyl programs alone or in combination with mowing across three sites. In the greenhouse, florpyrauxifen‐benzyl provided 86%–94% shoot control, reduced root biomass by ≥ 97% at the rosette stage and by ≥ 80% at the bolting stage, and lowered root bud regeneration to ≤ 14% of root segments, an effect comparable to that of glyphosate and clopyralid. In the field, sequential applications or mowing followed by florpyrauxifen‐benzyl significantly improved control (73%–79%) compared to a single spring application (69%) or single summer application (30%). Mixtures of florpyrauxifen‐benzyl with glufosinate or flazasulfuron did not improve control of C. arvense . Results indicate that florpyrauxifen‐benzyl effectively controls C. arvense through reductions in root biomass and inhibition of vegetative regeneration, with performance comparable to industry standards. These results support its use in perennial cropping systems, where it can be integrated with practices such as mowing or sequential applications to improve season‐long control and reduce flowering and seed production.