Difference in the impacts of the neonicotinoid dinotefuran administered through sugar syrup from that through pollen paste on a honeybee colony in the long-term field experiment

SummaryWe have previously examined the impact of neonicotinoid pesticides, dinotefuran and clothianidin, on honeybee Apis mellifera colonies in long-term field experiments when they were simultaneously administered through both vehicles of sugar syrup and pollen paste (Yamadaet al., 2012). The independent effect of a pesticide through two vehicles has not been studied in our previous work. In this paper, we investigated the independent impact of dinotefuran through each of the two vehicles. We confirmed that dinotefuran intake per bee until colony extinction due to administration through pollen paste (DF-TIPP) was roughly one-fifth as much as that through sugar syrup (DF-TISS). The intake was largely independent of dinotefuran concentration. We considered the possibility of DF-TIPP per bee as an indicator to assess the impact of persistent pesticide on a honeybee colony in a practical apiary.This work has replicated the finding that a honeybee colony has dwindled away to nothing after assuming an aspect of a colony collapse disorder (CCD) by administration of the neonicotinoids dinotefuran and clothianidin in our previous work, regardless of the vehicles. In addition, a failure in wintering was observed in case of administration of dinotefuran with the lowest concentration in this work even if the colony appeared vigorous before winter.We can infer that a CCD and a failure in wintering may have the same roots of chronic toxicity of neonicotinoids under conditions of low concentrations due to the persistency and high toxicity which are characteristic of them.