Are pesticide residues in honey related to oilseed rape treatments?

Pesticide treatments before and during the flowering of honey bee forage crops may lead to residues in
honey. In northern regions oilseed rape belongs to the main forage crops that is mostly cultivated by
means of intensive agriculture, including several pesticide treatments. However, in addition to the focal
forage crops, pesticides from non-forage crops can spread to wild flowers around fields, and thus the
residues in honey would reflect the whole range of pesticides used in the agricultural landscape. The aim
of our study was to clarify which currently used pesticides are present in honey gathered from heterogeneous
agricultural landscapes after the end of flowering of oilseed crops.
Honey samples (N ¼ 33) were collected from beehives of Estonia during 2013 and 2014, and analysed
for residues of 47 currently used agricultural pesticides using the multiresidue method with HPLC-MS/
MS and GC-MS and a single residue method for glyphosate, aminopyralid and clopyralid. Residues of
eight different active ingredients with representatives from all three basic pesticide classes were
determined. Although no correlation was detected between the cumulative amount of pesticide residues
and percent of oilseed crops in the foraging territory, most of the residues are those allowed for oilseed
rape treatments. Among all pesticides, herbicide residues prevailed in 2013 but not in 2014. Despite the
relatively small agricultural impact of Estonia, the detected levels of pesticide residues sometimes
exceeded maximum residue level; however, these concentrations do not pose a health risk to consumers,
also acute toxicity to honey bees would be very unlikely.

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