Insect Repellents May Disrupt Bumblebee Navigation

A new study has found that common insect repellents containing the chemical DEET may interfere with bumblebees’ ability to navigate back to their nests, raising concerns about the unintended ecological consequences of widely used pest control products on essential pollinators.

Researchers from the University of Bristol and the University of Stirling conducted laboratory experiments showing that exposure to DEET at levels comparable to those found in suburban environments disrupted the bees’ memory and spatial orientation. The study, published in the journal Proceedings of the Royal Society B, revealed that bumblebees exposed to DEET were significantly less likely to return to their nests after foraging, even when the scent trail leading home remained intact.

“We found that DEET doesn’t just repel insects — it can impair the cognitive functions bees rely on to find their way home,” said Dr. Elisa Frasnelli, lead author of the study and a researcher in sensory ecology at the University of Bristol. “Even low, environmentally relevant concentrations caused measurable deficits in navigation, which could reduce foraging efficiency and colony survival over time.”

Bumblebees depend on complex learning and memory systems to navigate landscapes, using visual landmarks and scent trails to travel between flowers and their nests. The researchers tested the insects in a controlled maze environment, where bees had to learn a route to a food source and then return to their nest. Those exposed to DEET showed delayed return times and increased errors in route selection, suggesting the chemical interfered with hippocampal-like brain functions involved in spatial memory.

The study did not find that DEET killed the bees or caused immediate physical harm, but rather that it induced sublethal behavioral changes. This distinction is important, as sublethal effects — while not immediately fatal — can still undermine pollinator health by reducing food collection, increasing vulnerability to predators, and lowering reproductive success in colonies.

Declines in wild pollinator populations, including bumblebees, have been documented across North America and Europe in recent decades. While habitat loss, pesticide exposure, climate change, and disease are considered primary drivers, this research suggests that everyday consumer products like insect repellents may contribute to the problem in ways previously overlooked.

DEET, or N,N-diethyl-meta-toluamide, has been the active ingredient in most commercial insect repellents since the 1950s. It is considered safe for human use when applied as directed and is approved by regulatory agencies including the U.S. Environmental Protection Agency (EPA) and the European Chemicals Agency (ECHA). However, its environmental impact on non-target insects has received less scrutiny.

Previous studies have shown that DEET can affect mosquitoes, ticks, and other arthropods, but its effects on beneficial insects like bees have been less studied. This research adds to a growing body of evidence suggesting that chemicals designed to repel pests may also disrupt non-target species through neurobehavioral pathways.

The researchers emphasized that their findings do not suggest people should stop using insect repellents, particularly in areas where mosquito-borne diseases pose a public health risk. Instead, they recommend further investigation into safer formulations and application practices that minimize environmental exposure.

“We need to balance human protection with ecological responsibility,” said Dr. Frasnelli. “Future repellent design should consider not just efficacy against biting insects, but also the potential impact on pollinators and other beneficial insects that support ecosystem health and food production.”

The study’s authors call for more field-based research to determine whether these laboratory findings translate to real-world settings, especially in urban and suburban gardens where both human repellent use and bumblebee foraging overlap. They also suggest that product labeling could eventually include environmental impact information, similar to how some pesticides now carry warnings about bee toxicity.

As pollinator decline continues to threaten biodiversity and agricultural productivity, understanding the full range of anthropogenic stressors — including those from everyday consumer products — is critical for developing effective conservation strategies. This study highlights the need for broader ecological evaluation of chemicals before widespread use, even when they are deemed safe for humans.