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Chronic High-Dose Neonicotinoid Exposure Decreases Overwinter Survival of Apis mellifera L.

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Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK S7N 5B4, Canada
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Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK S7N 5B4, Canada
*
Author to whom correspondence should be addressed.
Insects 2020, 11(1), 30; https://doi.org/10.3390/insects11010030
Received: 3 December 2019 / Revised: 20 December 2019 / Accepted: 28 December 2019 / Published: 31 December 2019
Overwinter colony mortality is an ongoing challenge for North American beekeepers. During winter, honey bee colonies rely on stored honey and beebread, which is frequently contaminated with the neonicotinoid insecticides clothianidin and thiamethoxam. To determine whether neonicotinoid exposure affects overwinter survival of Apis mellifera L., we chronically exposed overwintering field colonies and winter workers in the laboratory to thiamethoxam or clothianidin at different concentrations and monitored survival and feed consumption. We also investigated the sublethal effects of chronic thiamethoxam exposure on colony pathogen load, queen quality, and colony temperature regulation. Under field conditions, high doses of thiamethoxam significantly increased overwinter mortality compared to controls, with field-realistic doses of thiamethoxam showing no significant effect on colony overwinter survival. Under laboratory conditions, chronic neonicotinoid exposure significantly decreased survival of winter workers relative to negative control at all doses tested. Chronic high-dose thiamethoxam exposure was not shown to impact pathogen load or queen quality, and field-realistic concentrations of thiamethoxam did not affect colony temperature homeostasis. Taken together, these results demonstrate that chronic environmental neonicotinoid exposure significantly decreases survival of winter workers in the laboratory, but only chronic high-dose thiamethoxam significantly decreases overwinter survival of colonies in the field. View Full-Text
Keywords: thiamethoxam; clothianidin; sublethal; honey bee; winter; Canada thiamethoxam; clothianidin; sublethal; honey bee; winter; Canada
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Wood, S.C.; Kozii, I.V.; Medici de Mattos, I.; de Carvalho Macedo Silva, R.; Klein, C.D.; Dvylyuk, I.; Moshynskyy, I.; Epp, T.; Simko, E. Chronic High-Dose Neonicotinoid Exposure Decreases Overwinter Survival of Apis mellifera L.. Insects 2020, 11, 30.

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