Termites living inside a tree can be killed using chemical injections into the wood, bait stations placed around the base, or biological treatments like beneficial nematodes. The right approach depends on how far the infestation has spread and whether you’re trying to save the tree or remove it. Most active infestations in trees require direct treatment of the colony inside the wood, not just surface sprays.
Signs of Termites in a Tree
Before treating, confirm you’re actually dealing with termites. Look for mud tubes running up the trunk or along exposed roots. Subterranean termites build these pencil-width tunnels to travel between their underground colony and the wood they’re feeding on. Tapping the trunk may produce a hollow sound in areas where termites have eaten through the heartwood.
You might also notice small piles of wood-colored pellets (frass) near the base, which indicate drywood termites pushing waste out of their tunnels. Soft, crumbling wood at the base of the tree, swarms of winged termites near the trunk in spring, or visible damage where bark has fallen away are all reliable indicators. A tree can be heavily infested internally while looking relatively healthy on the outside, so probe any suspicious soft spots with a screwdriver to check the extent of the damage.
Foam Injection Into the Trunk
The most direct way to kill termites inside a tree is drilling into the infested wood and injecting insecticide foam. Foam formulations expand to fill internal cavities and tunnels, coating surfaces with a residual layer that kills termites on contact and through transfer between colony members. Two active ingredients commonly available in foam form are fipronil and imidacloprid. Fipronil-based foam (sold as Termidor Foam) and imidacloprid-based foam both work as fast-breaking foams that collapse quickly after application, leaving an even coating inside the wood.
To treat a tree this way, drill holes into areas where you’ve confirmed termite activity. Angle the drill bit to intersect galleries and hollow sections. Insert the foam applicator tip into each hole and apply for roughly 10 seconds or until foam begins to back-flow out of the hole. Hold the tip in place for about 5 seconds after you stop dispensing so the remaining foam in the applicator tube pushes into the treatment area. Seal the drill holes afterward with a tree-safe wound sealant or wooden plugs.
The key advantage of foam injection is that it treats the infestation directly where it lives. Fipronil in particular transfers between termites through physical contact, meaning workers that walk through the treated area carry the insecticide back to nestmates that never touched the foam themselves. This transfer effect can eliminate portions of the colony you couldn’t reach with the drill.
Bait Stations Around the Base
If the termites in your tree are subterranean (the most common type in North America), they maintain a colony underground and travel up into the tree to feed. Bait stations installed in the soil around the tree intercept foraging workers before or after they reach the trunk. The bait contains cellulose laced with a slow-acting insecticide that disrupts molting. Termites that consume it die within weeks when they attempt to shed their exoskeleton, a process they go through regularly.
Place bait stations about 1 to 2 feet from the base of the tree, spaced evenly in a ring. Commercial systems like Sentricon, Exterra, and Trelona Advance are designed for in-ground installation and are widely used by pest control professionals. The stations are checked periodically and refilled as termites consume the bait. Because the active ingredient works slowly, foraging termites share contaminated food with the rest of the colony before dying, which can collapse the entire colony over a period of weeks to months.
Baiting works well as a companion to direct injection. The foam kills what’s already inside the tree, while bait stations target the underground colony that sent the workers there in the first place. Without addressing the colony, surviving termites can simply return.
Beneficial Nematodes as a Biological Option
For a non-chemical approach, beneficial nematodes are microscopic worms that parasitize and kill insects in soil. The two species most commonly sold for pest control are Steinernema carpocapsae and Heterorhabditis bacteriophora. They’re available as commercial products formulated for use as soil drenches or sprays. You mix them with water and apply the solution to the soil around the tree’s base, where subterranean termites are active.
Nematodes have a solid track record against wood-boring insects in trees. Applications to trunks of dogwood infested with borers, for instance, have been shown to be quite effective. For termites, the nematodes enter the insects’ bodies, release bacteria that kill the host within 24 to 48 hours, and then reproduce inside the carcass to seek out more prey. Apply nematodes in the early morning or evening, since UV light kills them. Keep the soil moist for several days after application to help them survive and move through the ground. Soil temperature should be above 60°F for the nematodes to remain active.
Nematodes are less predictable than chemical treatments for large, established termite colonies, but they can reduce populations meaningfully and are safe for the tree, surrounding plants, pets, and people.
Liquid Soil Treatments
A liquid termiticide applied to the soil around and beneath the tree creates a chemical barrier that kills termites traveling between their underground colony and the trunk. Products containing fipronil, imidacloprid, or permethrin can be mixed with water and trenched into the soil in a continuous band around the tree’s root zone. This method works best for subterranean species and is often used alongside direct trunk treatment.
Dig a shallow trench (about 6 inches deep and 6 inches wide) around the tree at the drip line or closer to the trunk, pour the diluted termiticide into the trench, and backfill. The goal is to saturate the soil in the path termites use to reach the tree. Fipronil-based soil treatments can remain effective for years, creating long-term protection against reinfestation.
When the Tree Can’t Be Saved
A tree with extensive internal damage from termites may be structurally compromised even after the colony is eliminated. Termites eat the heartwood, which is the dense core that gives a tree its strength. If enough heartwood is gone, the tree becomes a falling hazard, especially in storms. Tap and probe the trunk at multiple heights. If large sections are hollow or soft, the tree may need to come down regardless of whether the termites are dead.
If you remove the tree, don’t leave the stump. Stumps are prime real estate for termite colonies, and an infested stump near your home creates a direct path to your foundation. Grind the stump below grade and treat the remaining wood and soil with a liquid termiticide to prevent the colony from simply relocating.
Preventing Reinfestation
Termites are attracted to moisture and decaying wood. Keep mulch pulled back at least a few inches from the trunk, since thick mulch traps moisture and gives termites cover. Remove any dead branches, woodpiles, or lumber stored near the tree. Improve drainage around the root zone if water tends to pool there.
Inspect the tree every few months for new mud tubes, fresh frass, or soft spots in the bark. If the tree is near your house, maintaining bait stations in the ground between the tree and the foundation adds a layer of early detection. Catching a new infestation early, before termites hollow out significant wood, gives you the best chance of saving the tree and keeping the colony from spreading to nearby structures.