A termiticide is any chemical product designed to kill or repel termites. These products work by creating treated zones in soil, wood, or bait stations that termites either cannot detect or cannot survive passing through. Termiticides are the primary tool used to protect buildings from the billions of dollars in structural damage termites cause each year, and they come in two main forms: liquid barriers applied to soil and bait systems placed in the ground around a structure.
How Termiticides Kill Termites
Termiticides attack termites through several biological pathways, depending on the active ingredient. Most work by disrupting the nervous system. Some block specific receptors in the brain, causing uncontrollable nerve firing that leads to paralysis and death. Others interfere with energy production inside cells, essentially starving termites at the cellular level even when food is available.
A separate class of termiticide takes a slower, more targeted approach. These are chitin synthesis inhibitors, which prevent termites from building new exoskeletons. Termites molt throughout their lives, shedding their outer shell to grow. When exposed to a chitin synthesis inhibitor, a termite cannot complete this molting process and dies. This mechanism is slow enough that affected termites return to the colony and spread the chemical before symptoms appear. In laboratory studies, just 5.5 milligrams of one such compound, picked up by foraging workers in 24 hours, was enough to kill a colony of roughly 59,000 individuals.
Repellent vs. Non-Repellent Formulas
Older termiticides, typically based on synthetic pyrethroid chemistry, work as repellents. They create a chemical fence that termites detect and avoid. This keeps termites out of a structure, but it doesn’t eliminate the colony. The termites simply forage elsewhere.
Non-repellent termiticides are invisible to termites. Because termites can’t sense these chemicals in treated soil, they walk through the treatment zone and pick up a lethal dose on their bodies. Before dying, they transfer the active ingredient to other colony members through normal grooming and contact. This “transfer effect” means non-repellent products can suppress or eliminate entire colonies, not just redirect them. Non-repellent liquids are applied as a continuous band around a structure, leaving no gaps for termites to slip through. This combination of colony elimination and complete perimeter coverage is why non-repellent termiticides have largely replaced repellent ones in professional pest control.
Liquid Barriers vs. Bait Systems
Liquid soil treatments are the traditional approach. A termiticide is mixed with water and applied to the soil around and beneath a building’s foundation, forming a continuous chemical barrier. For new construction, the soil is treated before the concrete slab is poured. For existing buildings, professionals dig trenches along foundation walls or use specialized rods to inject the product into the ground, typically to a depth of at least four feet. Application rates are precise: one gallon of diluted product per 10 square feet of soil surface, or one and a half gallons when the fill material is washed stone.
Bait systems take a different approach. Stations containing cellulose (a food termites seek out) laced with a slow-acting toxicant are placed in the ground around a structure, usually about three meters apart. When foraging termites find a station, they feed and carry the bait back to the colony. Bait systems use far less chemical than liquid treatments and can kill entire colonies. Their main limitation is coverage: the gaps between stations leave openings that foraging termites can pass through without encountering the bait, so they don’t provide the same continuous physical protection as a liquid barrier.
For subterranean termites, many professionals now recommend combining both methods or choosing non-repellent liquids that offer the colony-killing benefit of baits with the unbroken perimeter of a liquid treatment.
Common Active Ingredients
The U.S. Environmental Protection Agency lists several active ingredients currently registered for use in termiticides. The most widely used include:
- Fipronil: A non-repellent that causes hyper-excitation of the nervous system. Known for strong transfer effects between colony members.
- Imidacloprid: A non-repellent that blocks nerve signal receptors, causing paralysis. Highly water-soluble, which affects how it moves through soil.
- Bifenthrin: A repellent pyrethroid that disrupts nerve function. Binds tightly to soil particles, so it stays in the treated zone longer.
- Chlorantraniliprole: Acts on muscle fibers rather than nerves, causing progressive paralysis over time.
- Chlorfenapyr: A “pro-insecticide” that converts into its toxic form inside the termite’s body, then shuts down energy production at the cellular level.
Other registered pyrethroids include cypermethrin, cyfluthrin, esfenvalerate, and permethrin. For bait systems, chitin synthesis inhibitors like hexaflumuron and noviflumuron are the primary active ingredients.
Professional vs. Over-the-Counter Products
Consumer-grade termiticides, such as those sold at hardware stores, contain much lower concentrations of active ingredients than professional products. They’re designed for surface spraying and small-scale use. The problem is that termite control depends on complete, unbroken coverage of treated soil, and without professional trenching equipment or sub-slab injection tools, it’s nearly impossible to achieve the saturation needed for an effective barrier. Termites will find and exploit any gap in coverage.
Professional termite treatment requires specific licenses. Applicators typically hold structural pest control operator licenses and qualified applicator certifications. These requirements exist because the products are more concentrated and the application methods, which include trenching around foundations, drilling through concrete slabs, and injecting chemicals under pressure, carry real risks if done incorrectly.
EPA Performance Standards
Before any termiticide reaches the market, it must meet EPA registration requirements that include extensive toxicity testing, ecological impact assessment, and environmental fate data showing how the chemical behaves in soil and water. The EPA also sets measurable performance standards for approved products. Liquid termiticides used for structural protection must prevent 95% of wood damage for at least five years. Bait systems must achieve the same 95% protection level for at least three years. Wood preservative treatments face the strictest bar: 100% prevention of damage for a minimum of two years.
Environmental Concerns
Termiticides are designed to persist in soil, which is what makes them effective but also raises environmental questions. Leaching, the movement of chemicals downward through soil with rainwater, is the primary pathway for environmental contamination. How much a termiticide leaches depends heavily on its chemistry and the soil type.
Bifenthrin binds strongly to soil particles and tends to stay in the upper layers where it’s applied. Imidacloprid, by contrast, has low soil binding and high water solubility, giving it a much greater potential to move into groundwater. A U.S. Geological Survey study conducted from 1999 to 2005 detected imidacloprid in 13% of groundwater samples in areas with sandy, well-drained soil. Fipronil falls somewhere between the two in terms of mobility.
Leached termiticides can be toxic to non-target organisms, including beneficial soil insects, aquatic invertebrates, and pollinators. This indirect accumulation can also enter food chains. Researchers at UC Riverside have been investigating more targeted alternatives, including bistrifluron, a chitin synthesis inhibitor that killed roughly 95% of drywood termite colonies in testing with no documented off-target effects on mammals. Because it works specifically on insect molting biology, it poses less risk to non-insect species. Practical delivery methods for this compound are still being refined.