Evaluation of the appropriateness of pesticide administration-concentrations to honey bee Apis mellifera colony in long-term field experiments and modest proposal

Abstract

For investigating the effects of pesticides on bee colonies in actual apiaries, field experiments in an open environment are effective. It is natural to assume that the total food or pesticide intake taken by a honey bee colony includes their intakes from nature in addition to each administered in the field experiment. Therefore, in field experiments, setting the administration-concentration of pesticides for honey bee colonies is one of the most difficult tasks. The validity of pesticide concentrations administered to bee colonies was evaluated by various intakes of pesticides and foods obtained from five long-term field experiments conducted in Midwest Japan with distinct changes of four seasons and Maui, U.S.A. without cold winter. The author found a relationship, logPBD=logCP-2.4, between pesticide concentration (CP) and the average daily intake of pesticide ingested by one bee (PBD), and found that their ratio PBD/CP was about 1/250, which was significantly lower than the LD50 value. This fact supports that the concentration of pesticide administration in long-term field experiments conducted so far was not too high, but rather reasonable. In addition, the average daily intakes of sugar syrup and pollen paste ingested by one bee was found to be 3.1 mg/bee/day and 0.8 mg/bee/day, respectively, and notwithstanding their wide variation, be roughly constant regardless of the concentration of pesticides. I believe that this paper will help provide new guidelines for setting pesticide dosing concentrations, which have not been clear so far, in field experiments on the administration of pesticides to bee colonies.