Toshiro Yamada | Search bioRxiv

bioRxiv2015

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 (Yamada et 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.\n\nThis 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.\n\nWe 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.

Ecology↗

bioRxiv2015

Long-term field experiment on the impacts of the neonicotinoid dinotefuran and the organophosphate fenitrothion on a honeybee colony

SummaryNeonicotinoides are persistent and highly toxic pesticides that have become popular instead of organophosphates, being suspected to be a trigger of massive disappearance of bees that raises concern in the world. The evaluation of the long-term influence for a whole colony in the natural environment is, however, not established yet. In this paper, we conducted a long-term field experiment and found different impacts on honeybee colonies (Apis mellifera) in an apiary between the neonicotinoid dinotefuran and the organophosphate fenitrothion even though whose concentrations in sugar syrup provided for bees were adjusted to have nearly equal short-term effects on a honeybee based on the median lethal dose (LD50) as well as the insecticidal activity to exterminate stinkbugs.\n\nThe colony with administration of dinotefran (dinotefuran colony) became extinct in 26 days, while the colony with administration of fenitrothion (fenitrothion colony) survived the administration for the same period. Furthermore, the fenitrothion colony succeeded to be alive for more than 293 days after administration, and also succeeded an overwintering, which indicates that colonies exposed to fenitrothion can recover after the exposure.\n\nMeanwhile, the dinotefuran colony became extinct even though the intake of dinotefuran was estimated to be comparable with that of fenitrothion in terms of the LD50 of a honeybee. Moreover, the colonies in our previous long-term experiments where dinotefuran with higher concentration were administered only for first few days (Yamada et al., 2012) became extinct in 104 days and 162 days, respectively. From these results, we speculate that colonies exposed to dinotefuran hardly recover from the damage because dinotefuran is much more persistent than fenitrothion and toxic foods stored in cells can affect a colony in a long period.

Ecology↗