Sublethal effects of glyphosate‐based herbicides on a bumblebee: Behavioural disruption and transcriptomic responses under field‐realistic exposure

Abstract Pollinators are essential to global food security; however, their populations are declining due to habitat loss, pathogens and pesticide exposure. Glyphosate‐based herbicides (GCF) are the most widely used agrochemicals worldwide; however, their sublethal effects on bumblebees remain poorly understood. Here, we investigated the effects of field‐realistic GCF exposure on the buff‐tailed bumblebee ( Bombus terrestris ), integrating behavioural assays with transcriptomic analyses to uncover molecular mechanisms underlying observed physiological and behavioural changes. Bumblebees were exposed to low (1.3 g/L), medium (2.5 g/L) and high (4.7 g/L) GCF concentrations. High concentrations significantly increased mortality, whereas low and medium concentrations produced no lethal effects but altered feeding behaviour: sucrose consumption was suppressed while pollen intake increased, potentially as a compensatory mechanism. RNA sequencing revealed that GCF exposure upregulated stress response genes, including fatty acyl‐CoA reductases (FARs) involved in lipid metabolism, cuticular barrier function and detoxification pathways, while downregulating genes related to digestion, energy metabolism, neuromuscular function and cytoskeletal integrity. Notably, these transcriptional changes were partially reversible after a 4‐day recovery period on a clean diet. Functional enrichment analyses highlighted coordinated regulation across peroxisome, cutin/suberine/wax biosynthesis and longevity‐regulating pathways, suggesting integrated physiological responses to mitigate pesticide stress. These findings demonstrate that sublethal GCF exposure disrupts nutrient assimilation, energy allocation and mobility, providing mechanistic insight into the ecological risks of herbicide use for wild pollinators. Our results demonstrate the need to avoid high‐concentration applications and to incorporate sublethal and recovery dynamics into ecological and regulatory frameworks.