Effects of elevated CO₂ and temperature on cocklebur (Xanthium strumarium L.) and its herbicide response

Climate change, characterized by rising atmospheric CO₂ and temperature fluctuations, significantly alters crop-weed interactions and weed management efficacy. This study evaluated the interactive effects of elevated CO₂ (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).

Elevated CO₂ 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 CO₂ facilitated the translocation of trifloxysulfuron-sodium due to increased plant metabolism, thereby significantly lowering ED₅₀ values. In contrast, the efficacy of the soil-applied fluometuron remained highly stable and unaffected by variations in either CO₂ or temperature.

The interaction between climate change variables and chemical weed control is fundamentally driven by the herbicide's mode of action. While elevated CO₂ 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 & Sons Ltd on behalf of Society of Chemical Industry.