Our previous study was carried out to examine the impact of honeybee (Apis mellifera) colony in which a neonicotinoid was administered using both sugar syrup and pollen paste as vehicles in our long-term field experiments. However, the effect of each vehicle (food) administered on the pesticide of a honeybee colony has not been investigated. This study investigates the difference in the impact of the neonicotinoid pesticide dinotefuran on honeybee (A. mellifera) colony between the two vehicles of sugar syrup and pollen paste. A distinct difference was observed between the two vehicles: The per-bee intake of dinotefuran administered through pollen paste as a vehicle until colony extinction was roughly one-fifth of the per-bee intake administered through sugar syrup, independently of dinotefuran concentrations. This difference can be attributed to the dissimilarity in strength of the impact on honeybee colony between worker bees which preferentially take sugar syrup (honey) to pollen paste and a queen bee and brood (larvae) which take pollen paste (bee bread) in preference to sugar syrup as a result of the long-lasting toxicity of dinotefuran. This suggests that pollen as a protein source contaminated by neonicotinoid pesticides can cause deeper adverse effect on a honeybee colony than honey as an energy source. A honeybee colony to which dinotefuran was administered becomes extinct after showing the appearance of a colony collapse disorder, as in the case of a colony administered with dinotefuran through both vehicles as reported in our previous study. It is inferred that a long-persistent pesticide such as neonicotinoid causes an overwintering failure due to the existence of toxicity of the pesticide in honey and bee bread stored in a hive which last even during overwintering.

Key words: Honey bee, sugar syrup, pollen paste, dinotefuran, pesticide, neonicotinoid, field experiment, long-term, colony, CCD, failure in wintering, collapse.