Plant protection product (PPP) deposition through drift into non-treated off-crop areas (e.g. biodiversity promotion or flower strips) can negatively affect wild and managed bees. In the authorisation process for PPPs, these risks are taken into account based on regulatory laboratory studies, semi-field and field trials, as well as theoretical models based on published data. This process was developed and validated for treated agricultural areas (i.e., in-crop). However, for off-crop areas there are significant uncertainties regarding PPP deposition via spray drift and the resulting exposure of bees due to direct toxic effects and indirect effects due to contamination of nectar and pollen of adjacent plants. The aim of this project was to investigate the vertical distribution and deposition of spray drift into flower strips at the edge of a field during insecticide treatments with Spinosad or Acetamiprid. Potential adverse effects on Osmia bicornis exposed to drift-treated flower strips under tunnel conditions were evaluated. PPP residues in nectar, pollen, food provisions for larvae and plant material were quantitatlvely analysed using UHPLC‑MS/MS and the survival of female O. bicornis and their reproduction success (i.e., total offspring produced, brood mortality, hatching rate, sex-ratio) were evaluated. Results from the PPP residue analyses are currently being determined and will be presented later. However, our data revealed PPP exposed females had a significantly reduced presence in the nesting units for both the Spinosad (27.3%; P < 0.001) and Acetamiprid (65.7%; P < 0.01) treatments when compared to the non-treated control treatments (73.6%). Furthemore, reproductive success was statistically significantly reduced (P < 0.001) in the Spinosad treatment, whereas the Acetamiprid treatment did not differ from the controls. Taken together, our data suggest that drift residues of these two PPPs can indeed adversely affect the fitness of O. bicornis and that current protective measures based on regulatory studies with honey bees are likely not sufficient to safeguard solitary bees.
