Effects of elevated <scp>CO</scp> ₂ and temperature on cocklebur ( <scp> <i>X</i> </scp> <i>anthium strumarium</i> L.) and its herbicide response

Abstract Background Climate change, characterized by rising atmospheric CO 2 and temperature fluctuations, significantly alters crop‐weed interactions and weed management efficacy. This study evaluated the interactive effects of elevated CO 2 (400, 600, 800, and 1000 ppm) and temperature regimes (26/16°C and 29/19°C) on the biomass accumulation of Xanthium strumarium and the efficacy of two herbicides with distinct modes of action: trifloxysulfuron‐sodium (systemic, ALS inhibitor) and fluometuron (soil‐active, PSII inhibitor). RESULTS Elevated CO 2 concentration up to 1000 ppm at the optimal temperature (26/16°C) significantly stimulated the vegetative growth and dry biomass of X. strumarium . Crucially, dose–response analyses revealed that this climate‐driven accelerated growth did not induce herbicide resistance; rather, it increased the weed's susceptibility to the systemic herbicide. Elevated CO 2 facilitated the translocation of trifloxysulfuron‐sodium due to increased plant metabolism, thereby significantly lowering ED 50 values. In contrast, the efficacy of the soil‐applied fluometuron remained highly stable and unaffected by variations in either CO 2 or temperature. CONCLUSION The interaction between climate change variables and chemical weed control is fundamentally driven by the herbicide's mode of action. While elevated CO 2 acts as a fertilizer for X. strumarium , the resulting rapid growth paradoxically increases the efficacy of systemic herbicides by accelerating the movement of active ingredients. Meanwhile, soil‐active herbicides like fluometuron offer a climate‐resilient weed management strategy. Future studies should incorporate molecular approaches to fully elucidate these mode‐of‐action‐specific physiological responses under changing climatic conditions. © 2026 The Author(s). Pest Management Science published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry.