Risk Assessment of Effects of Essential Oils on Honey Bees (Apis mellifera L.)

Authors: Caren, Joel; Zhu, Yu Cheng; Read, Quentin; Du, Yuzhe

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2025
Publication Date: 3/12/2025
Citation: Caren, J.R., Zhu, Y., Read, Q.D., Du, Y. 2025. Risk assessment of essential oils toward honey bees (apis mellifera l.). Insects. 16:3. https://doi.org/10.3390/insects16030303.
DOI: https://doi.org/10.3390/insects16030303

Interpretive Summary: The impact of synthetic pesticides on non-target organisms has led to increased interest in environmentally friendly pest control methods, such as essential oils. To ensure these natural compounds are safe for pollinators, it is essential to assess their effects on honey bees. This study assessed the impacts of one commercially available essential oil mixture (EcoTec+) and four essential oil components (ß-bisabolene, cinnamaldehyde, 1,8-cineole, and eugenol) on honey bee workers in the lab. EcoTec+ increased a protective protein. Bisabolene decreased protective enzymes with no lethal effect. Cinnamaldehyde also caused decreased protective enzyme activity and displayed toxicity when ingested. Cineole only inhibited one of the four enzymes measured. Eugenol suppressed one protective enzyme and was toxic on contact. Collectively, the essential oils studied did not pose a significant danger to honey bees and seem to be a generally safe alternative to certain synthetic pesticides.

Technical Abstract: Toxicity of synthetic pesticides to non-target organisms has prompted a shift towards more en-vironmentally friendly agricultural pest control methods, including essential oils as possible bi-opesticides. Before these natural chemicals can be widely adopted for protecting food supplies and human health, it is crucial to evaluate their impacts on pollinators, such as honey bees. In this study, we examined the effects of one commercially available essential oil mixture (EcoTec+) and four essential oil components (ß-bisabolene, cinnamaldehyde, 1,8-cineole, and eugenol) on honey bee workers using feeding or spray treatment. We then assessed the responses of esterase (EST), glutathione-S-transferase (GST), acetylcholine esterase (AChE), and P450. EcoTec+ increased a P450 transcript, while bisabolene inhibited EST, AChE, and P450, without being lethal. Cin-namaldehyde exhibited toxicity when ingested, suppressing AChE and P450. Cineole inhibited P450 transcripts. Eugenol suppressed EST and was toxic on contact. Overall, the essential oils tested did not cause acute lethal toxicity to honey bees; however, their biochemical effects varied, mostly remaining sublethal. These findings suggest that these essential oils could be considered safe for use around honey bees.