Amelioration of acute and chronic toxicity of imidacloprid by dietary phytochemicals in honey bees (apis mellifera)
Honey bees (Apis mellifera) provide important pollination services to the U.S. agricultural enterprise, valued at more than $15 billion per year. However, colonies have been declining due to multiple stressors, including parasites, pests, diseases, pesticides, nutrition, and modern beekeeping practices. In particular, the neonicotinoid imidacloprid has been targeted as a potentially strong contributor to colony decline. Imidacloprid is a systemic pesticide, and honey bees are challenged by its presence in nectar, pollen, water, and beeswax. In the presence of imidacloprid, honey bees upregulate cytochrome P450 enzymes, which are implicated in their detoxification; because consumption of the phytochemicals quercetin and p-coumaric acid, common constituents of honey and beebread, also upregulates cytochrome P450 monooxygenases, the presence of these compounds in the diet of honey bees may ameliorate the toxic effects of imidacloprid. In order to determine the effect of quercetin and/or p-coumaric acid on honey bees in the presence of imidacloprid, both acute and chronic toxicity bioassays were conducted. Honey bee imidacloprid LC50 values, the median lethal concentrations, were determined in the presence of field-realistic levels of quercetin and/or p-coumaric acid. Additionally, longevity assays were conducted with one-day-old bees at varying field-realistic concentrations of imidacloprid in the presence of quercetin and/or p-coumaric acid. The phytochemicals had no significant effect on the LC50 of imidacloprid. However, at concentrations of 0, 15, and 45 ppb imidacloprid, p-coumaric acid significantly increased honey bee longevity. Quercetin also significantly increased honey bee longevity at 15 ppb imidacloprid but had an antagonistic effect on p-coumaric acid in the absence of imidacloprid. These results indicate that these two phytochemicals may play an important role in detoxification activity at low levels of imidacloprid but lose their protective effect at higher concentrations. This study thus reinforces the importance of considering the interactions between phytochemicals and other xenobiotics when evaluating honey bee health.
quercetin, imidacloprid, p-coumaric acid
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign