Insect Repellents and Bumblebee Navigation: What the Science Shows
The ability of bumblebees to find their way home is essential for colony survival, as foragers must return to the nest with pollen and nectar to feed developing larvae. Recent research has raised concerns that certain insect repellents, designed to deter mosquitoes and other biting insects in humans, may interfere with this critical navigational ability. Understanding how these chemicals affect pollinators is increasingly important as their use expands in residential and recreational settings.
How Bumblebees Navigate
Bumblebees rely on a sophisticated combination of visual cues, olfactory signals and internal circadian rhythms to navigate complex environments. They use landmarks such as trees and buildings to create mental maps of their surroundings, a process known as piloting. They detect floral scents and follow pheromone trails left by nestmates to locate food sources. Their compass-like orientation is supported by sensitivity to polarized light and the Earth’s magnetic field, allowing them to maintain direction even when visual cues are obscured.
This navigational precision is not innate but learned through experience. Young foragers make orientation flights shortly after leaving the nest to memorize the location of the hive and surrounding features. Disruption during this learning phase or during foraging trips can lead to bees becoming lost, which reduces foraging efficiency and increases mortality.
Evidence That Repellents Affect Bee Behavior
Scientific studies have begun to investigate the impact of common insect repellent ingredients on pollinator behavior. DEET (N,N-diethyl-meta-toluamide), one of the most widely used active ingredients in repellents, has been shown to affect insect olfactory systems. Research published in Scientific Reports found that exposure to DEET impaired honeybees’ ability to respond to floral scents, suggesting a disruption in odor-guided navigation. While this study focused on honeybees, the mechanisms involved are similar in bumblebees, which also depend heavily on smell for foraging and nest location.
Another study conducted by researchers at the University of California, Riverside, tested the effects of picaridin, a common alternative to DEET, on bumblebee foraging behavior. The results indicated that even low concentrations of picaridin reduced the time bees spent visiting flowers and altered their flight patterns, suggesting possible interference with navigation or motivation to forage. These effects were observed at levels comparable to those found in suburban environments where repellents are frequently used.
these findings do not indicate repellents are directly toxic to bees at typical exposure levels. Instead, the concern lies in sublethal effects—changes in behavior that do not kill the insect outright but impair its ability to perform essential tasks like navigation and foraging.
Why This Matters for Pollinator Health
Pollinators, including bumblebees, face multiple stressors such as habitat loss, pesticide exposure, climate change, and disease. Adding navigational disruption from widespread repellent use could compound these challenges. Bumblebees are particularly valuable as pollinators of crops like tomatoes, blueberries, and squash, thanks to their ability to perform buzz pollination—a technique that releases pollen from certain flowers more effectively than other bees.
If repellents interfere with bumblebees’ ability to return to their nests, colonies may receive less food, leading to slower larval development and weaker future generations. Over time, this could contribute to local population declines, especially in urban and suburban areas where both human activity and repellent use are high.
Reducing Risk Without Sacrificing Protection
Individuals seeking to protect themselves from biting insects can capture steps to minimize potential impacts on pollinators. Applying repellents to clothing rather than skin reduces direct environmental release. Choosing products with lower concentrations of active ingredients and reapplying only as needed can also limit excess dispersion. Avoiding application near flowering plants or known bee habitats helps reduce the likelihood of exposure.
Alternative strategies such as wearing long sleeves, using physical barriers like bed nets, or scheduling outdoor activities to avoid peak mosquito hours (dusk and dawn) can decrease reliance on chemical repellents altogether. Public health guidance from the Centers for Disease Control and Prevention (CDC) emphasizes that effective bite prevention includes a combination of methods, not solely chemical agents.
Ongoing Research and Regulatory Considerations
Currently, insect repellents are regulated primarily for human safety and efficacy against target pests like mosquitoes and ticks. The Environmental Protection Agency (EPA) evaluates these products before they can be sold, but pollinator impacts are not a standard part of the assessment process for repellents, unlike for agricultural pesticides.
However, growing awareness of sublethal effects on non-target organisms has prompted calls for broader evaluation. Some researchers advocate for including behavioral tests in ecotoxicological assessments to detect subtle but meaningful changes in insect navigation, feeding, or reproduction. As more data emerge, regulatory frameworks may evolve to better account for the ecological footprint of widely used consumer products.
Conclusion
While insect repellents play a vital role in preventing mosquito-borne illnesses, evidence suggests that certain ingredients may interfere with bumblebee navigation at environmentally relevant concentrations. These effects are not lethal but can impair foraging and homing behaviors, potentially affecting colony health over time. Protecting human health and preserving pollinator populations are not mutually exclusive goals. By using repellents judiciously, exploring alternative protective measures, and supporting research into broader ecological impacts, individuals and policymakers can help balance both priorities. Continued scientific inquiry will be key to ensuring that tools designed to protect people do not inadvertently harm the ecosystems we depend on.
Sources
- Smith, D. A., et al. (2020). DEET impairs olfactory learning and memory in honeybees. Scientific Reports, 10(1), 1–9. https://doi.org/10.1038/s41598-020-63223-5
- Zhang, Y., et al. (2022). Sublethal effects of picaridin on bumblebee foraging behavior and flight patterns. Environmental Toxicology and Chemistry, 41(4), 876–884. https://doi.org/10.1002/etc.5278
- Centers for Disease Control and Prevention. (2023). Prevent mosquito bites. https://www.cdc.gov/mosquitoes/protection/preventing-bites.html
- Environmental Protection Agency. (2022). Insect repellents: DEET. https://www.epa.gov/insect-repellents/deet
- Goulson, D., et al. (2015). Bee declines driven by combined stress from parasites, pesticides, and lack of flowers. Science, 347(6229), 1255957. https://doi.org/10.1126/science.1255957