Assessment of current use pesticides in flowers, pollen provision, and wild bees: HPLC-ESI-MS/MS method development and field implementation

Synthetic pesticide use is a major driver of pollinator declines in agricultural landscapes. To understand the impact of pesticides, it is essential to quantify residues in food resources and in insects themselves. We developed simple, fast, and cost-effective multiresidue methods for the simultaneous quantification of up to 83 current use pesticides (CUPs) in flowers (0.5 g sample weight) and 71 CUPs in pollen provision (0.1 g sample weight) via liquid chromatography-tandem mass spectrometry. Additionally, methods were developed for individual wild bees (Osmia bicornis), enabling the analysis of 65 CUPs in 0.02 g samples (females) and 45 CUPs in 0.01 g samples (males). The extractions used acidified acetonitrile (2.5% formic acid), with phase separation assisted by ammonium formate and clean-up via freeze-out. The validation showed limits of quantification between 0.00025 mg/kg and 0.05 mg/kg for flowers, 0.0002 mg/kg to 0.052 mg/kg for pollen provision, 0.0002 mg/kg to 0.08 mg/kg for female bees, and 0.00008 mg/kg to 0.1 mg/kg for male bees. The methods were applied to flowers, pollen provision, and post-pupal bees from agricultural sites. In total, 47 CUPs were detected in flowers, 35 in pollen provision, and 4 in post-pupal bees, with herbicides being most prevalent. This study highlights the exposure of pollinators to CUP mixtures, including emerging bees that have not yet been active in the environment. Our methods provide practical tools for monitoring CUP residues in small environmental samples, supporting the assessment of exposure in plant-insect matrices.