Honey bees for pesticide monitoring in the landscape: Which bee matrices should be used?

Among bee species, the western honey bee (Apis mellifera) is preferred in monitoring studies performed in the agricultural landscape, while bee matrices, pollen, and honey are mostly a subject of these studies due to their unique composition. A justified question about the relevance of other bee matrices, like larvae, foragers, beebread, and/or wax, has been raised. The ability of different bee matrices (wax, pollen grains, bee bread, foragers, larvae, nectar, and honey) to absorb pesticide residues is subjected in this study. All samples were collected during a crop flowering season (oilseed rape) on intensively managed agricultural land in Slovakia and Germany. The observed high variability in residue levels, profile, and number of detections among studied matrices from Germany, west, and east Slovakia gave us an assumption of the use of different agricultural practices between these two countries. Fungicides clearly dominated across all samples in all sampling regions. The increased pesticide profile positively correlated with the oilseed rape pollen grains in pollen pellets and/or bee bread. Bee wax, pollen, and bee bread showed a high number of detected active substances and total residue concentrations among matrices, indicating their high ability to absorb pesticide residues in the surrounding hive environment.