Beebread consumption by honey bees is fast: results of a six-week field study

Due to their foraging behavior, honey bees interact with the landscape. As a result, honey bees and their brood will be exposed to pesticides through nectar and pollen entering the hive. Although these pathways seem rather straightforward, there are several steps between the entry of nectar and pollen and its consumption by the colony. One of the aspects involved here is the time between collection and consumption of pollen in the hive. This is of importance for the actual exposure of nurse bees and larvae to pesticides in pollen. Although lab and short-term field studies indicated that bees prefer to consume freshly stored pollen, this has to our knowledge not been verified in a long-term field study under realistic environmental and apiculturist conditions. To study pollen consumption dynamics, influx and consumption were recorded at 3 or 4 day intervals over a six-week period in two colonies. It was demonstrated that throughout the experimental period, beebread consumption was high in the first 3 to 5 days after collection, over which approximately 70% was consumed. The remaining 30% was consumed within a 2 to 3 week period. Pollen consumption is swift and indicates that only limited time is available for potential degradation processes. As actual data on degradation of pesticides in stored pollen are not available, a justified worse case assumption would be that the actual exposure concentrations consumed by the nurse bees and larvae are the same as the concentrations in collected pollen.