Drywood termites are experts at staying out of sight. They live inside wooden structures, quietly feeding and expanding their colonies where homeowners may not notice them until damage is already underway. But their hidden lifestyle also depends on a vulnerable biological process: molting.
Researchers at the University of California, Riverside have shown that bistrifluron, a chemical that blocks the formation of new termite exoskeletons, can destroy drywood termite colonies by interfering with the insects’ ability to grow. The findings were published in the Journal of Economic Entomology. In laboratory testing, the treatment killed about 95 percent of a colony without the mammal toxicity concerns linked to many traditional termite control methods.
A Safer Way To Target Termites
“This chemical is more environmentally friendly than ones traditionally used for drywood termite infestations,” said Nicholas Poulos, corresponding author of the paper and a doctoral student in UCR’s Department of Entomology. “It’s specific to insects and can’t harm humans.”
The reason the chemical is so targeted comes down to the termite body plan. Humans have bones inside their bodies. Termites wear their support system on the outside in the form of an exoskeleton. That outer shell is built largely from chitin, a tough natural material also found in fungal cell walls, fish scales, and the beaks of squids and octopi.
For insects, chitin is essential. It gives the exoskeleton strength, helps shield the body, and provides anchoring points for muscles. When termites grow, they must shed their old exoskeleton and build a new one. Drywood termites go through this process about seven times during their lives.
Bistrifluron interrupts that step. Instead of poisoning termites in a broad, fast acting way, it prevents them from making the chitin they need for their next protective shell.
“Once the termites reach a certain stage, they have to molt. They cannot avoid that,” said Dong-Hwan Choe, UCR entomology professor and senior paper author. “With a lethal dose of this chemical, they’ll try to shed their old exoskeleton but won’t have a new one ready to protect them.”
Termites Spread the Treatment Themselves
The effect is not instant. The researchers saw that bistrifluron first made the termites less active and reduced their feeding. Over time, the chemical blocked successful molting, and the insects died.
The 2025 study tested three chitin synthesis inhibitors against the western drywood termite, Incisitermes minor. Bistrifluron worked faster than chlorfluazuron and noviflumuron at the tested rates. In one no choice test, bistrifluron produced 99 percent mortality over 60 days. In a choice test using a 0.1 percent rate, it produced 96 percent mortality over the same period.
The most important part may be how the chemical travels. After termites fed on treated wood, they passed material to other members of the colony. In transfer tests, even when only 5 percent of termites had been exposed, the groups reached 100 percent mortality by day 90. The study reported that food material moved from exposed donor termites to unexposed recipients within 24 to 48 hours.
That finding fits with newer UC Riverside work highlighting how western drywood termites share food and essential gut microbes through proctodeal trophallaxis, a mouth to anus feeding behavior that is difficult to observe because the insects live almost entirely inside wood. Those hidden social behaviors can make infestations hard to detect, but they may also help treatments spread once termites contact treated material.
“It’s been successfully used on subterranean termites, which are also important structural pests,” Choe said. “But native western drywood termites are also important, especially in California.”
A Slower Collapse With Big Advantages
Once drywood termites consume the treated wood, the compound can move through the colony as termites interact. Full colony collapse takes roughly two months, making it slower than some conventional methods. But the tradeoff could be worth it: lower toxicity, more targeted action, and the potential for a localized treatment that does not require tenting an entire home.
“We believe this method of spot treatment can kill a larger colony and spread more easily than current termite control methods,” Choe said. “You don’t have to apply too much to get a very good result. The chitin synthesis inhibitors show promise as localized treatment for drywood termites.”
Traditional fumigation remains a major burden for homeowners. It can be toxic, disruptive, and stressful. People often have to bag food, leave the house, and wait before returning. It also does not prevent termites from coming back later.
“Low-impact strategies like this one will become an attractive option in many cases. Furthermore, the chemical may stay active in the wood for some time, potentially providing protection from future infestations,” Choe said.
A Chemical Lure Could Make Treatment Stronger
The UCR team has also explored another clever way to improve termite control: using scent to draw termites toward treated wood. In earlier work, Choe’s lab studied pinene, a pleasant smelling chemical released by forest trees. To western drywood termites, pinene can signal food.
When termites follow that scent into insecticide treated wood, the treatment becomes more effective. A 2025 patent application from UCR describes the use of pinenes to improve localized insecticide injections against western drywood termites. It states that adding pinene to localized treatments killed termites more quickly and increased final mortality compared with insecticide alone. The application also suggests that pinene could allow wider spacing between drill holes and may reduce the time, labor, and amount of insecticide needed for treatment.
“We saw significant differences in the death rates using insecticide alone versus the insecticide plus pinene,” said Choe. “Without pinene, we got about 70% mortality. When we added it in, it was over 95%.”
Making It Practical for Homes
The bistrifluron study used acetone to dissolve the chemical before applying it to wood. That worked for the research, but it is not ideal for real world use because acetone is flammable and has a strong odor.
“We are working to make it more feasible for practical application in real life scenarios,” Poulos said.
That next step matters because western drywood termites are a serious structural pest. They are native to northern Mexico and California, and they are especially important in California. The species has also been introduced to other regions, including Hawaii, New York, Florida, Canada, China, Japan, Korea, and Australia, according to the 2025 study. Movement of lumber and other wood products helps transport termites, while their concealed lifestyle inside wood makes them difficult to manage.
Climate change may add to the problem. As temperatures shift, the termites may be able to expand into places that were once less suitable for them.
“As we move lumber around the world, the termites are constantly transported to new locations. If they find the climate there acceptable, the problem will spread,” Choe said. “In areas where these termites are common, it’s just a matter of time before homes are infested, so this study is a good initial step toward alternative strategies for controlling them.”