Expanding the species in toxicity testing: Dimethoate sensitivity in wild bumblebees links morphological traits to...

Pesticides represent a major threat to pollinators' health. Bumblebees, as essential pollinators, are one of the bees severely impacted by pesticide exposure. The lack of sensitivity data across diverse species hinders the breeding and application of pesticide-tolerance pollinators trains. This study assessed the acute oral toxicity of dimethoate, an organophosphorus insecticide and a positive control in environmental risk assessments, in five bumblebee species: the commercial European bumblebee species Bombus terrestris and four wild Chinese native bumblebee species (B. ignitus, B. ganjsuensis, B. pyrosoma, and B. lantschouensis). The 48-h median lethal doses (LD₅₀) were determined as follows: 1.64 μg/bee for B. terrestris, 0.98 μg/bee for B. ignitus, 0.91 μg/bee for B. ganjsuensis, 0.71 μg/bee for B. pyrosoma and 0.70 μg/bee for B. lantschouensis. Morphological traits including body wight and forewing length were measured, revealing a positive correlation between them and a negative relationship between body weight and sensitivity to dimethoate. These results indicate that easily measurable morphological traits like body weight could serve as potential indicators to predicting dimethoate tolerance in bumblebees. Our findings are of importance for bumblebee toxicology, addressing the knowledge gap in non-commercial bumblebees of pesticide sensitivity. By expanding acute toxicity data to include underrepresented wild species, this study provided valuable insights for selecting and breeding pollinator strains with enhanced insecticide tolerance, highlighting the need for a broader species range in toxicity tests.