Contamination of wild plants near neonicotinoid seed-treated crops, and implications for non-target invertebrates

5 Neonicotinoid insecticides are commonly-used as seed treatments on flowering crops such as 6 oilseed rape. Their persistence and solubility in water increase the chances of environmental 7 contamination via surface-runoff or drainage into areas adjacent to the crops. However, their 8 uptake and fate into non-target vegetation remains poorly understood. In this study, we 9 analysed samples of foliage collected from neonicotinoid seed-treated oilseed rape plants and 10 also compared the levels of neonicotinoid residues in foliage (range: 1.4 – 11 ng/g) with the 11 levels found in pollen collected from the same plants (range: 1.4 – 22 ng/g). We then analysed 12 residue levels in foliage from non-target plants growing in the crop field margins a ge: . 13 – 106 ng/g). Finally, in order to assess the possible risk posed by the peak levels of neonicotinoids 14 that we detected in foliage for farmland phytophagous and predatory insects, we compared the 15 maximum concentrations found against the LC50 values reported in the literature for a set of 16 relevant insect species. Our results suggest that neonicotinoid seed-dressings lead to 17 widespread contamination of the foliage of field margin plants with mixtures of neonicotinoid 18 residues, where levels are very variable and discontinuous, but sometimes overlap with lethal 19 concentrations reported for some insect species. Understanding the distribution of pesticides in 20 the environment and their potential effects on biological communities is crucial to properly 21 assess current agricultural management and schemes with biodiversity conservation aims in 22 farmland. 23