Recent fieldwork by Sussex University demonstrates that the current focus on exposure to pesticides via the crop overlooks an important factor: throughout spring and summer, mixtures of neonicotinoids are also found in the pollen and nectar of wildflowers growing in arable field margins, at concentrations that are sometimes even higher than those found in the crop. Water-soluble neonicotinoids travel from agricultural fields into the soil beneath wildflower strips.  The large majority (97%) of neonicotinoids brought back in pollen to honey bee hives in arable landscapes was from wildflowers, not crops.

Both previous and ongoing field studies have been based on the premise that exposure to neonicotinoids would occur only during the blooming period of flowering crops and that it may be diluted by bees also foraging on untreated wildflowers. This study shows that exposure is likely to be higher and more prolonged than currently recognized because of widespread contamination of wild plants growing near treated crops.

http://pubs.acs.org/doi/abs/10.1021/acs.est.5b03459

http://www.soilassociation.org/news/newsstory/articleid/8703/-new-research-exposes-secret-cocktail-of-toxic-pesticides-in-hedgerows-and-wildflowers