Mixtures of an insecticide, a fungicide and a herbicide induce high toxicities and systemic physiological disturbances in winter Apis mellifera honey bees

• Published in: Ecotoxicology and environmental safety Vol. 203; p. 111013
• Main Authors: Almasri, Hanine, Tavares, Daiana Antonia, Pioz, Maryline, Sené, Déborah, Tchamitchian, Sylvie, Cousin, Marianne, Brunet, Jean-Luc, Belzunces, Luc P.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 15.10.2020; Elsevier
• Subjects: Animal biology; Animals; Bees - physiology; Cocktail effects; Dioxolanes - toxicity; Drug Synergism; Ecology, environment; Fungicides, Industrial - toxicity; Glycine - analogs & derivatives; Glycine - toxicity; Glyphosate; Herbicides - toxicity; Insecticides - toxicity; Life Sciences; Neonicotinoids - toxicity; Neurons and Cognition; Nitro Compounds - toxicity; Pesticide mixtures; Pesticides - toxicity; Physiological state; Pollination - drug effects; Psychology and behavior; Synergy; Triazoles - toxicity; Winter honey bee; Pesticide mixtures; Winter honey bee; Synergy; Cocktail effects; Physiological state; Cocktail effect
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2020.111013

Multiple pesticides originating from plant protection treatments and the treatment of pests infecting honey bees are frequently detected in beehive matrices. Therefore, winter honey bees, which have a long life span, could be exposed to these pesticides for longer periods than summer honey bees. In this study, winter honey bees were exposed through food to the insecticide imidacloprid, the fungicide difenoconazole and the herbicide glyphosate, alone or in binary and ternary mixtures, at environmental concentrations (0 (controls), 0.1, 1 and 10 μg/L) for 20 days. The survival of the honey bees was significantly reduced after exposure to these 3 pesticides individually and in combination. Overall, the combinations had a higher impact than the pesticides alone with a maximum mortality of 52.9% after 20 days of exposure to the insecticide-fungicide binary mixture at 1 μg/L. The analyses of the surviving bees showed that these different pesticide combinations had a systemic global impact on the physiological state of the honey bees, as revealed by the modulation of head, midgut and abdomen glutathione-S-transferase, head acetylcholinesterase, abdomen glucose-6-phosphate dehydrogenase and midgut alkaline phosphatase, which are involved in the detoxification of xenobiotics, the nervous system, defenses against oxidative stress, metabolism and immunity, respectively. These results demonstrate the importance of studying the effects of chemical cocktails based on low realistic exposure levels and developing long-term tests to reveal possible lethal and adverse sublethal interactions in honey bees and other insect pollinators. •Pesticide combinations are more toxic to honeybees than individual pesticides.•Increased concentrations of pesticides are not always linked to increased toxicity.•Pesticides modulate feeding behavior through an increase in food consumption.•Pesticides individually or in combination induce strong physiological perturbations.•The response to exposure to pesticides is systemic and tissue-specific.