Drywood termite treatment is a more surgical process than subterranean termite soil treatment. Because the colony lives entirely inside the wood, the treatment needs to reach the gallery network directly. Two DIY methods are effective for accessible infestations: foam injection, which delivers an insecticide into the gallery to kill workers and reproductives on contact, and borate surface treatment, which penetrates the surrounding wood and kills any colony members that consume or contact treated wood. Used together, they address both the active colony and the surrounding wood that the colony might migrate into.
This guide covers localized treatment for infestations in accessible wood such as attic framing, window frames, door frames, exposed structural members, and furniture. If your inspection has found active drywood termite colonies in multiple locations throughout the structure, or in areas inside finished walls or roofing that cannot be reached without demolition, whole-structure fumigation is the more reliable path. The criteria for making that decision are in the how to get rid of termites guide.
What You Will Need
For foam injection you need an aerosol termite foam product (Termidor Foam and BioAdvanced Termite Killer Foam are the most widely available DIY options) with an included or compatible injection nozzle, a drill with a 3/16 to 1/4 inch bit to match the nozzle diameter, a probe wire for gallery mapping, wood filler or wood putty, and sandpaper. For borate surface treatment you need a borate product such as Tim-bor or Bora-Care, a bucket for mixing, and a brush, roller, or pump sprayer for application. Chemical-resistant gloves and safety glasses are required for both treatments. Product comparisons, active ingredient details, and purchasing options are in the best termite foam guide.
Step 1: Locate the Frass and Identify the Kickout Hole
The frass pile is your starting point. Find the accumulation of dry, hexagonal pellets on the surface below the infested wood, then locate the kickout hole directly above it in the wood surface. The hole is small, typically about 1 mm in diameter, and may be sealed with a thin fecal membrane between clearing events. Mark it clearly with a pencil. This kickout hole is the point through which the colony has been pushing frass out of the gallery, and it serves as your primary injection entry point and the reference for determining gallery direction.
If the frass pile is under furniture or a window sill, check the underside and the edges of the wood component above it carefully before assuming the kickout hole is on the most visible surface. Drywood termite kickout holes are sometimes on the underside or back face of wood components where they are less exposed.
Step 2: Map the Gallery Direction and Extent
Drywood termite galleries run parallel to the wood grain, branching and widening as the colony grows. Insert a thin stiff wire into the kickout hole gently to determine the direction the gallery runs and roughly how deep it extends. Then use the handle of a screwdriver to tap along the wood surface in both directions from the kickout hole, listening for the change from a solid sound to a hollow sound that indicates gallery space beneath. This tapping test maps the extent of the gallery before drilling and tells you where to place your injection holes to maximize foam coverage through the network.
Step 3: Drill Injection Holes Along the Gallery Path
Using a drill and a bit sized to match your foam injector nozzle, drill holes into the wood at 6 to 8 inch intervals along the mapped gallery path. The first hole can be made directly through or immediately adjacent to the kickout hole if it is large enough for the nozzle. Angle each hole slightly toward the gallery center so the nozzle directs foam into the open gallery rather than into solid wood beside it. Clean cuts are easier to fill and seal after treatment, so use a sharp bit and avoid splintering the surface.
In attic framing and other structural lumber, drill into the exposed face or edge of the member. In window and door frames, drill into the interior face if possible to keep injection holes out of the most visible surface. In furniture, drill into the underside or back wherever possible.
Step 4: Inject Foam Through Each Hole
Insert the foam injector nozzle fully into the first drilled hole and depress the aerosol trigger in short bursts, waiting a second between each burst to allow the foam to expand before adding more. The foam expands significantly on contact with air inside the gallery, and overfilling a small gallery section will force foam back out of the injection hole before it has traveled far. Work in short bursts and watch for foam to appear at the adjacent hole, which signals that the gallery between those two points is filled. Move systematically along the gallery from one injection hole to the next until all mapped sections have been treated.
Pay particular attention to any branches in the gallery that the probe wire identified. Foam that reaches a branch junction will expand in both directions, but branches that extend beyond the treated zone should receive their own injection hole if the gallery mapping indicates they are extensive.
Step 5: Allow Foam to Cure and Seal All Holes
The foam requires time to cure after injection before the holes are sealed. Follow the product label for the curing time, which is typically 30 to 60 minutes. During this period, keep the area undisturbed. After curing, press wood filler firmly into each injection hole and into the original kickout hole until it is flush with the surrounding surface. Allow the filler to dry completely according to the product’s instructions, then sand smooth. The sealed surface can then be primed and painted or finished to match the surrounding wood.
Step 6: Apply Borate Surface Treatment to Surrounding Wood
Borate surface treatment addresses two things that foam injection alone cannot: the risk that the colony has gallery sections that the foam did not reach, and the surrounding wood that the colony might migrate into if any reproductives survived the foam treatment. Mix Tim-bor or Bora-Care to the label dilution rate in a clean bucket. Apply the solution generously to all accessible wood surfaces within approximately two feet of the treatment area using a brush, roller, or pump sprayer, working the solution into any cracks, joints, and end grain where penetration is deepest.
For attic framing treatments, extend the borate application to all exposed rafters, joists, and sheathing in the affected section. The borate remains effective in the wood indefinitely as long as the wood stays dry, making this a lasting preventive barrier around the treated area. Do not apply paint or film-forming sealant over the borate surface until the borate solution has dried fully into the wood, as surface sealers can trap moisture and reduce penetration.
Step 7: Monitor for Continued Frass Activity
Check the treated area for new frass daily for the first two weeks after treatment, then weekly for the following two months. If the injection holes were properly sealed, any new frass that appears indicates an active gallery section that the foam did not reach. Repeat the drilling and injection process for any new frass locations. A drywood termite colony that continues to produce frass after two injection treatments in the same area, or that begins producing frass in new locations adjacent to the treated zone, suggests either a larger colony than localized treatment can address or a second independent colony in the same piece of wood. In that case, review the decision criteria in the how to get rid of termites guide before investing in additional localized treatment.