Network meta-analysis: Acute mortality effects of neonicotinoid insecticides clothianidin, imidacloprid, thiacloprid, thiamethoxam on bumblebee (Bombus spp.)

Neonicotinoid insecticides are extensively used to manage piercing-sucking pests, but their toxicity profile in bumblebee remains a subject of ongoing debate. This study systematically searched PubMed, ProQuest, ScienceDirect, and Web of Science to perform conventional and network meta-analyses on extracted data. Molecular docking was also conducted on the nicotinic acetylcholine receptors (nAChRs) of bumblebees, aphids, and whiteflies, the binding free energies and key amino acid residues were recorded. Five studies met the inclusion criteria. None of the four neonicotinoids significantly increased acute bumblebee mortality at low exposure concentrations. At medium and high concentrations, clothianidin, imidacloprid, and thiamethoxam were significantly associated with acute mortality. Thiacloprid showed no significant acute lethality at medium concentrations but induced lethal effects at high concentrations. Molecular docking revealed that all four compounds bound to a similar binding pocket in the bumblebee nAChR. This study recommends the cautious application of neonicotinoid insecticides during flowering periods and in areas with bumblebee activity. Large-scale, standardised laboratory and field studies are warranted to evaluate the sublethal effects and long-term ecological impacts.