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

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 the extent of such contamination in organic fields and ecological focus areas (EFAs) are currently unclear. 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. 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. Finally, we calculated hazard quotients (HQs) and potentially affected fractions for 72 beneficial and 12 pest species. Under a field-realistic scenario, we found that between 5.3%-8.6% of above-ground invertebrate species may be exposed to lethal concentrations of clothianidin, and 31.6%-41.2% to sublethal concentrations, in integrated production and conventional fields. We also found that 1.3%-6.8% (up to 12.5% based on HQs) of the beneficial invertebrate species may be exposed to sublethal concentrations of neonicotinoids in EFAs and organic fields. In contrast, no pest species would be exposed to lethal concentrations, even under a worst-case scenario. Synthesis and applications. Our study suggests that diffuse contamination by neonicotinoids may harm a significant fraction of non-target beneficial species. The use of neonicotinoids on crops may threaten biodiversity in refuge areas, while also potentially jeopardizing the practice of organic farming by impeding the biological control of pests. On the basis of our results, we call for a reduction in the dispersion and overuse of neonicotinoid insecticides in order to prevent any detrimental effects on biodiversity and ecosystem services associated with agroecosystems.