Bistrifluron, an insect growth regulator developed and tested at the University of California, Riverside, wipes out termite colonies in lab trials while leaving the people who apply it unharmed, according to researchers who spent years testing it against the western drywood termite. The chemical works by blocking chitin synthesis, cutting off a termite’s ability to build a new exoskeleton each time it molts.
Nicholas Poulos, the doctoral student who led the testing in Dong-Hwan Choe’s entomology lab at UC Riverside, said the appeal of the compound is its narrow target. “It’s specific to insects and can’t harm humans,” Poulos said, describing a mode of action that leaves mammals’ biology untouched because people do not molt an exoskeleton.
Termites cause billions of dollars in structural damage across the United States every year, and drywood species are notoriously difficult to treat because colonies can sit hidden inside wall studs and roof framing for years before anyone notices the damage. A chemical that can be applied to a single infested beam rather than an entire house, as later coverage of the research framed it, is the kind of result that keeps getting recirculated among pest-control researchers long after the original study appeared.
More than 95 percent mortality in lab colonies
In choice tests, where termites could pick between treated and untreated wood, bistrifluron produced 95.7% mortality; when the insects had no alternative to the treated wood, mortality rose to roughly 99%, according to UC Riverside’s account of the results. Choe explained the mechanism in blunt terms: once a termite reaches a certain stage, it has to molt, and a lethal dose leaves it trying to shed an old exoskeleton with no new one ready underneath.
The effect also spreads through a colony without every termite needing direct exposure. Groups in which only 5% of termites were initially exposed to bistrifluron still reached 100% mortality by day 90, according to the peer-reviewed study Poulos, Choe and their co-authors published in the Journal of Economic Entomology. Termites pass food and fluids among nestmates through a behavior called trophallaxis, and the researchers found that habit was enough to carry a lethal dose from a small number of exposed workers to the rest of the group.
Bistrifluron was not the only chitin synthesis inhibitor the team tested. The published results describe it killing termites significantly faster than two other compounds in the same class, chlorfluazuron and noviflumuron, across both the choice and no-choice trials. That speed matters in practice: a slower-acting compound gives termites more time to detect and avoid a treated area before a lethal dose spreads through the colony.
An alternative to fumigating the whole house
Standard treatment for a drywood termite infestation today usually means fumigating the entire structure with sulfuryl fluoride gas. The University of California’s own pest-management guidelines note that residents must vacate a fumigated home for several days, that tarpaulins dragged across a roof during setup can damage it, and that fumigation leaves no lasting residue to prevent a future infestation, according to UC’s statewide integrated pest management program.
Bistrifluron points toward something narrower: a spot treatment applied to localized infestations rather than an entire home. Only a small amount is needed “to get a very good result,” Choe said, an efficiency that matters because the chemical is currently dissolved in acetone, a flammable, strong-smelling solvent that researchers acknowledge is not yet a practical off-the-shelf product.
That gap between a lab result and a shelf-ready product is not small. Getting an insect growth regulator into a form pest control technicians can apply safely and consistently, at a price that competes with fumigation, typically takes years of formulation work after the biology is proven. Manufacturers also have to register any new termiticide formulation with the Environmental Protection Agency before it can be sold, a process that runs on its own timeline separate from the underlying academic research.
A pest expanding its range
Western drywood termites are native to northern Mexico and California, but researchers who study them say the species is pushing farther north as the climate warms, according to trade reporting on the lab’s work. Choe has also pointed to global lumber shipping as a separate route by which drywood termites keep turning up in new places, since infested wood can carry a colony far from where it started.
Nothing about that timeline is settled yet.
The findings, first published online in March 2025 and drawing renewed attention from science outlets more than a year later, have not yet translated into a commercial product on pest control trucks. Choe’s lab has said bistrifluron has already found use against subterranean termites, a related but distinct structural pest responsible for the bulk of termite damage claims nationwide, which suggests a path toward market use exists even if the timeline for drywood applications remains unresolved.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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