Glyphosate is the world’s most widely used herbicide, sprayed on everything from soybean fields to suburban lawns. A study published in the Journal of Experimental Biology now adds a specific, measurable cost to that ubiquity: honeybees exposed to sublethal doses of the chemical foraged 13% less after just three days, and their brains showed altered levels of the amino acids and neurotransmitters that govern behavior.
What the researchers did
A team led by Laura C. McHenry, then a Ph.D. student in Virginia Tech’s Department of Entomology (now a postdoctoral researcher at Penn State), worked with senior author Margaret J. Couvillon, associate professor of entomology at Virginia Tech, along with co-authors Roger Schürch, McAlister Council-Troche, Aaron D. Gross, Lindsay E. Johnson, and Bradley D. Ohlinger. The team set up two artificial feeding stations for free-flying honeybee colonies: one laced with a sublethal concentration of glyphosate, the other clean. Bees were trained to visit the stations and their foraging behavior was tracked over several days, after which the researchers analyzed brain chemistry — specifically the balance of biogenic amines, the signaling molecules that help regulate insect behavior, learning, and motivation.
What they found
Bees that fed at the glyphosate-laced station showed a 13% decline in foraging activity within three days, compared with bees at the untreated station. Their brains also showed shifts in amino acids and biogenic amines that were not present in unexposed bees — evidence that a sublethal dose, well below what would kill a bee outright, can still measurably disrupt the neurochemistry underlying foraging behavior.
The doses involved didn’t kill any bees or produce obvious signs of acute poisoning. That’s the point of the study: sublethal exposure is the realistic scenario for most foraging bees in agricultural and suburban landscapes, where glyphosate residues on treated plants are common but rarely at lethal concentrations. A behavioral change that’s invisible to a beekeeper — bees still leaving the hive, still visiting flowers — can still add up to a real cost at the colony level.
As Couvillon’s team notes, a 13% reduction in foraging is not a trivial number for a colony that depends on a constant flow of nectar and pollen. Fewer successful foraging trips can mean reduced pollination effectiveness for the crops and wild plants bees visit, and less stored honey for the colony to draw on, particularly during periods when forage is already scarce.
Why sublethal effects matter for pollinator health
Most regulatory testing for agricultural chemicals has historically focused on acute lethality — does a given dose kill the organism. Sublethal-effects research like this study asks a harder, more policy-relevant question: what does a chemical do to an organism that survives exposure at real-world field concentrations? Glyphosate itself is a herbicide, not an insecticide, and was long assumed to have limited direct biological effects on insects. A growing body of research, including this study, has been narrowing that assumption by looking specifically at behavior and neurochemistry rather than mortality alone.
For honeybees, which are managed pollinators responsible for a substantial share of global crop pollination, even modest reductions in individual foraging efficiency can compound across a colony and a season. That makes sublethal-effects data a meaningful input for beekeepers, growers, and the regulatory bodies that set label restrictions and buffer requirements for herbicide use near active hives.
Funding and disclosure
The research was supported by a competitive grant from the USDA’s National Institute of Food and Agriculture (NIFA), the federal agency that administers competitive agricultural and food-system research funding, along with a graduate student research grant from Virginia Tech’s Department of Entomology. That funding chain — a federal competitive award paired with an internal departmental graduate grant — is a common and clearly disclosed pattern in agricultural entomology research, and one that research offices tracking federal award compliance and acknowledgment language will recognize.
Publication timeline
The study, “Sublethal glyphosate exposure reduces honey bee foraging and alters the balance of biogenic amines in the brain,” was first published online in the Journal of Experimental Biology on 6 May 2025 and appeared in print in Volume 228, Issue 9 (May 2025), DOI 10.1242/jeb.250124. It received wider public attention starting in early August 2026 following renewed press coverage of the findings, including a Virginia Tech-sourced release picked up by ScienceDaily on August 4, 2026. The underlying science hasn’t changed since the 2025 publication — the current news cycle reflects a fresh round of coverage of an already peer-reviewed result, not a new study.
What to watch
The authors’ framing points toward two open questions worth tracking: whether the same sublethal foraging and neurochemical effects hold up across different glyphosate formulations and field-realistic exposure routes (contaminated pollen and nectar versus a controlled feeding station), and whether the 13% foraging decline translates into a measurable colony-level effect on honey yield or pollination service over a full season. Both are natural next steps for a research group that has already established the underlying behavioral and neurochemical signal.
Primary source: McHenry, L.C., Schürch, R., Council-Troche, M., Gross, A.D., Johnson, L.E., Ohlinger, B.D., and Couvillon, M.J. (2025). “Sublethal glyphosate exposure reduces honey bee foraging and alters the balance of biogenic amines in the brain.” Journal of Experimental Biology 228(9), jeb250124. DOI: 10.1242/jeb.250124.
