Location: Southern Horticultural ResearchTitle: Effects of coumaphos and imidacloprid on honey bee (Hymenoptera: Apidae) mortality in laboratory experiments
|GREGORC, ALES - Mississippi State University|
|ALBURAKI, MOHAMED - University Of Southern Mississippi|
|RINDERER, NICHOLAS - University Of Southern Mississippi|
|KNIGHT, PATRICIA - Mississippi State University|
|KARIM, SHAHID - University Of Southern Mississippi|
Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2018
Publication Date: 10/9/2018
Citation: Gregorc, A., Alburaki, M., Rinderer, N., Sampson, B.J., Knight, P., Karim, S., Adamczyk Jr, J.J. 2018. Effects of coumaphos and imidacloprid on honey bee (Hymenoptera: Apidae) mortality in laboratory experiments. Scientific Reports. 8:15003. https://doi.org/10.1038/s41598-018-33348-4.
Interpretive Summary: We designed laboratory bioassays that enabled us to compare the effects of two common insecticides on honey bee lifespan, feeding rate, mortality, and stress levels based on gene expression. Newly emerged worker honey bees were exposed to coumaphos and imidacloprid insecticides, as well as their mixtures. Coumaphos induced significantly higher bee mortality, which was associated with a increased physiological stress, particularly to the insecticide mixture, whereas, low doses of imidacloprid by themselves did not kill bees outright. A mix of coumaphos and imidacloprid did reduce bee feeding rate.
Technical Abstract: The main objective of this study was to bioassay comparatively the effects of two common insecticides on honey bee Apis mellifera worker’s lifespan, food consumption, mortality, and expression of antioxidant genes. Newly emerged worker bees were exposed to organophosphate insecticide, coumaphos, a neonicotinoid imidacloprid, and their mixtures. Toxicity tests were conducted along with bee midgut immunohistological TUNEL analyses. RT-qPCR assessed the regulation of 10 bee antioxidant genes linked to pesticide toxicity. We tested coumaphos at 92.6 ppm concentration, in combination with 5 and 20 ppb imidacloprid. Coumaphos induced significantly higher bee mortality, which was associated with a down regulation of catalase compared to coumaphos and imidacloprid (5/20 ppb) mixtures, whereas, both imidacloprid concentrations independently had no effect on bee mortality. Mixture of coumaphos and imidacloprid reduced daily bee consumption of patty to 10 mg from a coumaphos intake of 14.3 mg and (18.4 and 13.7) mg for imidacloprid (5 and 20) ppb, respectively. In the case of insecticide mixtures, only down-regulation of antioxidant genes were recorded along with noticeable midgut tissue damage, while intensive up-regulation was observed for antioxidant genes as well as less midgut apoptosis when bees were fed 20 ppb imidacloprid.