A nation-wide survey of neonicotinoid insecticides in agricultural land with implications for agri-environment schemes

1. Neonicotinoids are the most widely used class of insecticides globally. However, the link between farming practices and the extent of contamination of soils and crops by neonicotinoid insecticides, as well as and the extent of such contamination in organic fields and ecological focus areas (EFAs) are currently unclear. 2. We measured the concentrations of five neonicotinoid insecticides (imidacloprid, clothianidin, thiamethoxam, thiacloprid, acetamiprid) in 702 soil and plant samples in 169 cultivated fields and EFAs from 62 conventional, integrated production and organic farms distributed over the entire lowland of Switzerland. 3. We detected neonicotinoids in 93% of organic soils and crops, and more than 80% of EFA soils and plants – two types of arable land supposedly free of insecticides. We also tested 16 samples of organic seeds, of which 14 were positive for neonicotinoids. 4. Finally, we calculated hazard quotients (HQs) and potentially affected fractions for 72 beneficial a...