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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Publications at this Location » Publication #374328
Research Project: Modeling Honey Bee Exposure to Pesticides in Pollination Dependent Crops of California

Location: Invasive Species and Pollinator Health

Title: Context-dependent effect of dietary phytochemicals on honey bees exposed to a pesticide, thiamethoxam

Author
item Seshadri, Arathi
item BERNKLAU, ELISA - Colorado State University

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2021
Publication Date: 8/10/2021
Citation: Seshadri, A.H., Bernklau, E. 2021. Context-dependent effect of dietary phytochemicals on honey bees exposed to a pesticide, thiamethoxam. Journal of Insect Science. 21(4). Article 11. https://doi.org/10.1093/jisesa/ieab053.
DOI: https://doi.org/10.1093/jisesa/ieab053

Interpretive Summary: Honey bees continue to face challenges resulting from habitat loss related compromises to nutrition, exposure to agrochemicals and devastating pests and pathogens. Honey bees depend on plants for their nutritional needs. Pollen and nectar produced by plants, in addition to protein, lipids and carbohydrates, provide bees with a wealth of micronutrients including phytochemicals such as flavanols and alkaloids. The long-standing mutualism between plant and pollinators have enabled bees to coevolve benefits to such phytochemicals that are plant defense compounds. Earlier studies demonstrated that phytochemical supplementation to worker bees increased their longevity and pathogen tolerance. Testing the effects of phytochemicals on pesticide tolerance, a context dependent effect was detected in bees fed with 2 sub-lethal doses (1ppb and 10ppb) thiomethoxam, a neonicotinoid. At 1ppb phytochemical supplementation increased longevity but at 10ppb longevity was reduced suggesting a negative synergistic effect at the higher sub-lethal dose. Mortality (%) of forager-aged bees was higher than expected at 1ppb implying an effect of toxin accumulation in bees exposed to thiomethoxam during ontogeny. Given that phytochemical composition of pollen and nectar varies between plant species, our findings suggest that the negative impacts of agrochemicals on bees may vary across crops depending on the phytochemicals in pollen and nectar.

Technical Abstract: Nutrition, key to healthy populations of organisms, determines their responses to stressors. Habitat loss impacts availability and access to optimal nutrition, the effects of which are evident in the challenges faced by pollinators that feed on floral pollen and nectar. In addition to macronutrients, flowers contain phytochemicals that provide bees with secondary benefits such as increased longevity and pathogen tolerance. Our study aims to understand the role of phytochemicals in pesticide tolerance. Bees were fed with 2 sub-lethal doses (1ppb and 10ppb) thiomethoxam, a neonicotinoid, in sugar solution supplemented with 25ppm of caffeine, kaempferol, gallic acid or p-coumaric acid. The effect was context dependent—at 1ppb phytochemical supplementation increased longevity but at 10ppb longevity was reduced suggesting a negative synergistic effect. In addition, mortality (%) of forager-aged bees was higher than expected at 1ppb implying an effect of toxin accumulation. Phytochemical composition of pollen and nectar varies between plant species. Our findings suggest that the negative impacts of agrochemicals on bees may vary across crops depending on the phytochemicals in pollen and nectar. Understanding the phytochemical composition of individual crops is important for the use of appropriate agrochemicals that minimize harm to pollinators while effectively controlling pests.