From field to food II - will pesticide-contaminated pollen diet lead to a contamination of worker jelly?

Residues of pesticides have been found in bee collected pollen and stored beebread. Pollen is the protein source for bees and hence important for nurse bees to produce larval food. However, the fate of pesticides in the pollen used for larval food production is not clarified. We conducted a feeding experiment with free-flying mini-hives of the honey bee, Apis mellifera. A mixture of 13 different substances in high concentrations (156-9021 mu g/kg) was offered inside the hive. During the time of feeding, worker larvae of known age were reared. At larval age three to six days, worker jelly (WJ) was harvested and subjected to a multi-pesticide residue analysis. Concentrations of the detected pesticides in the WJ increased with larval age and ranged from 2.9 to 871 mu g/kg for three- to six-day-old larvae, depending on the pesticide. The amount of pesticides significantly correlates with the amount of pollen grains in the worker jelly with increasing larval age from 41 to 4654 pollen/mg WJ. Thus, we hypothesize the addition of pollen to the WJ to be responsible for the pesticide residues in the WJ. For the first time, this study shows the real pesticide exposure of honey bee larvae to pesticides by larval food. Our results should help to better evaluate the concentrations found in the field and to conduct field realistic feeding experiments, which may be used for risk assessments or pesticide approval.