Spatiotemporal dissipation, metabolic dynamics and bumblebees' toxicity risk of the neonicotinoid insecticide thiacloprid in greenhouse conditions.

Some neonicotinoids have been restricted in outdoor environments due to their risks to pollinating insects, yet their safety for non-target organisms in greenhouses is still unknown. This study investigates the deposition, degradation, and metabolic dynamics of thiacloprid on greenhouse-grown tomato and assesses its toxicity risk to pollinating bumblebees from spatial and temporal perspectives. Spatially, thiacloprid initially concentrated in leaves (71 %) and flowers (23 %), with deposition in the upper plant being 1.5 times that of the lower sections. The compound's half-life varied by plant tissue: flowers (3.28 days), fruits (4.04 days), stems (4.13 days), and leaves (10.37 days), with the upper sections 1.05-1.75 times higher than in the lower sections of the same organ. Five primary metabolites were identified in tomato tissues, peaking in leaves and flowers 5-7 days. Additionally, greenhouse thiacloprid exposure affected bumblebee body weight, mortality, and pollinated fruit weight. The risk quotient index further proves that thiacloprid residues in leaves and flowers posed an exposure risk to bumblebees, with risk levels subsiding below threshold values after 5 days in flowers and 21 days in leaves. The findings provide an important reference for the exposure risk and safe use supervision of neonicotinoid insecticides to pollinating insects in greenhouse scenarios.