Glyphosate disrupts honeybee brains, foraging drops 13%

A study published on August 6, 2026, in the Journal of Experimental Biology reveals that glyphosate, the world’s most-used herbicide, disrupts honeybee foraging and brain chemistry. The research, led by Associate Professor Margaret Couvillon and Ph.D. student Laura McHenry from Virginia Tech’s Department of Entomology, found that exposure to glyphosate caused a 13 percent decline in foraging activity and altered neurochemicals in bees.

Honeybees are affected because they frequently encounter glyphosate while foraging in agricultural fields, gardens, and landscapes where the weedkiller is applied. The study notes that glyphosate is not usually fatal to bees, but the sublethal effects—comparable to drowsiness from an antihistamine—can impair their behavior. A 13 percent reduction in foraging, if colony-wide, could decrease pollination effectiveness, honey production, and threaten colony survival, according to Couvillon.

The findings matter because honeybees are critical pollinators, and glyphosate is widely used. The researchers detected chemical changes in amino acids and neurotransmitters in exposed bees, which may explain the behavioral shifts. This suggests that even non-lethal herbicide exposure can undermine colony stability, raising concerns about current usage practices.

The study, supported by a grant from the National Institute of Food and Agriculture and a graduate student grant from Virginia Tech’s Department of Entomology, involved training bees to visit feeders with and without glyphosate. After three days, the exposed bees showed the foraging decline and brain chemistry changes. McHenry, now a postdoctoral researcher at Penn State, emphasized the need for strategic regulatory choices to minimize harm.

Background research had assumed glyphosate was safe for bees because they lack the enzyme it targets in plants. However, this study challenges that assumption by demonstrating sublethal neurological effects. The researchers call for more work to understand how glyphosate-based weedkillers interact with bee biology under real-world conditions, given the frequent contact between bees and the herbicide.

Next steps include improved regulation, careful application strategies, and further research to protect pollinators. The study underscores that the consequences for bees may be more significant than previously understood, as glyphosate’s widespread use increases the likelihood of exposure and potential harm to colonies.