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ARS Home » Southeast Area » Stoneville, Mississippi » Pollinator Health in Southern Crop Ecosystems Research » Research » Publications at this Location » Publication #405034
Research Project: Ecological Assessment and Mitigation Strategies to Reduce the Risks of Bees to Stressors in Southern Crop Ecosystems

Location: Pollinator Health in Southern Crop Ecosystems Research

Title: Feeding toxicity of abamectin on honey bees (Apis mellifera)

Author
item Zhang, Weiqiang
item Zhu, Yu Cheng
item Lau, Pierre
item Zeigler, Amy

Submitted to: Entomology Society America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/14/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pesticide exposure is one of the major stressors affecting honey bee health. This study investigated the short- and long-term effects of an insecticide, abamectin, on honey bee health. A formulated abamectin, Agri-Mer® SC (AM), was used in our feeding study at three concentrations of abamectin: 20, 44, and 100 ppb. We also tested the effect of pure abamectin and used proper controls in this study. Honey bees were monitored for 21 days after the administration of the pesticide. Our data showed a dose- and time-dependent toxicity of AM and pure Abamectin on honey bees; for example, after exposure to 100, 44, and 20 ppb of the a.i. of AM, bees started to die at 6 h, 12h, and 24-48 h, respectively. The average mortality rate upon exposure to AM on Day 1 was 0.17% (20 ppb), 2.1% (44 ppb), and 23% (100 ppb), whereas on Day 7 was 18.2% (20 ppb), 59% (44 ppb), and 93% (100 ppb). For the 100 ppb treatment groups, all bees died within 14 days. (Note: the data was from three independent experiments with 516-520 bees in each treatment group). Pure Abamectin produced a similar toxic effect on honey bees as AM did. Our study helps gain insight into how abamectin exerts toxicity on honey bees and find new ways to improve honey bee health.

Technical Abstract: Pesticide exposure is one of the major stressors affecting honey bee health. This study investigated the acute and long-term sublethal effects of abamectin on honey bee. Agri-Mer® SC (AM, formulated abamectin), pure abamectin, and a negative control were administered orally to 4-day-old honey bee workers through sucrose solution spiked with study chemicals. A cage containing 20 bees was treated as a replicate. Treated bees were monitored daily for 21 days. Our data showed a dose- and time-dependent toxicity of AM and pure abamectin on honey bees; for example, after exposure to 100, 44, and 20 ppb of the active ingredient of AM, bees started to die at 6 h, 12h, and 24-48 h, respectively. The average mortality rate upon exposure to AM on Day1 was 0.17% (20 ppb), 2.1% (44 ppb), and 23% (100 ppb), whereas on Day 7 was 18.2% (20 ppb), 59% (44 ppb), and 93% (100 ppb). For the 100 ppb treatment groups, all bees died within 14 days. Abamectin is a Class 6 insecticide acting by modulating chloride channels in insects. Since chloride channels are major ion channels affecting the water and fluid homeostasis in the gut of many species and several chloride channels have been identified in the honey bee gut, the toxicity of abamectin on honey bees could be attributable to, at least in part, its adverse effect on honey bees’ digestive system. Further study is needed to investigate this possibility and find ways to minimize adverse impact of abamectin on honey bee health.