Key Takeaways
- Powderpost beetles destroy wood from the inside out — the fine sawdust (frass) you see is a sign damage has already been done.
- More common in Atlantic Canada than termites; found in hardwood floors, structural timbers, and old furniture.
- Active infestations can be treated; old, inactive damage doesn’t require action but should be documented.
- Your home inspector can identify signs of activity; a pest specialist confirms and treats.
Termites get most of the attention when it comes to wood-destroying insects, but in Atlantic Canada the bigger practical concern is usually powderpost beetles. I find evidence of them fairly regularly — in sub-areas, in hardwood flooring, in structural timbers, in antique furniture. They're quiet, slow-moving, and easy to overlook. And because they spend most of their lives hidden inside the wood they're eating, they can cause significant damage before anyone knows they're there.
If you're buying an older home, or a home with a crawl space or older hardwood floors, it's worth understanding what you're looking for.
There's more than one kind
When people say "powderpost beetles" they're usually talking about one of three groups, and they behave somewhat differently. It's worth knowing the distinction because it affects where you look, what you find, and how you respond.
True powderpost beetles (Lyctinae)
These are the ones most people mean. They attack hardwoods only — oak, ash, hickory, walnut, mahogany — because they lay their eggs inside the large pores that hardwoods have and softwoods don't. Bamboo articles and furniture are also commonly infested. The frass (the fine dust they produce) is the consistency of talcum powder or baking flour — almost impossibly fine. Exit holes are very small and round, about the size of a pinhead.
The good news with true powderpost beetles is that they prefer wood with a high starch content, and as wood ages and dries out, the starch diminishes. Wood with a moisture content below about 8% is generally too dry for infestations to take hold. Most infestations in furniture or flooring were introduced in the wood before it reached the home — in the lumber yard, the millwork shop, or the furniture manufacturer.
Deathwatch beetles (Anobiidae)
Deathwatch beetles are a bigger concern structurally, because they're not as fussy about their wood. They'll attack both hardwoods and softwoods, and they're particularly fond of older, slightly damp structural lumber — the kind you find in sub-areas, basements, and the lower framing of older homes. They need wood with a moisture content above about 14% to thrive, which is why you find them where moisture problems exist.
Their frass is slightly grittier than the true powderpost variety — more like fine sand than powder. They also leave small pellets packed into their tunnels, which is a useful identification clue. Exit holes are slightly larger. And, famously, adult deathwatch beetles communicate by tapping their heads against the walls of their tunnels at night — which is where the name comes from. In old houses, before modern insulation, that faint ticking sound was audible in quiet rooms, and became associated with sitting beside the dying.
False powderpost beetles (Bostrichidae)
False powderpost beetles are less common in residential settings but can appear in tropical hardwoods like lauan or Philippine mahogany, sometimes used in panelling or furniture. Their exit holes are notably larger than the other two groups, and their frass is packed tightly into the gallery rather than falling out — which is why it can be harder to spot from a distance. A distinguishing characteristic: if you try to blow or dislodge the frass from the hole, it resists. With true powderpost beetles, it falls out easily.
How to spot evidence of an infestation
The most reliable signs, in order of what I look for:
- Exit holes. Small, clean, round holes in the surface of the wood are the clearest indicator. They're created when adult beetles chew their way out of the wood after completing their larval stage. The size varies by species — roughly 1–2 mm for true powderpost, slightly larger for deathwatch and false powderpost. Fresh holes look clean-edged; old holes may be discoloured or filled with debris.
- Frass on or below the wood. Fine powdery dust collecting on surfaces below infested wood, or spilling from the exit holes, is a strong indicator. With true powderpost beetles it genuinely looks like flour or talcum powder. With deathwatch, it's slightly coarser — more like fine sand. Either way, if you see pale dust accumulating under a joist or beam, look up.
- The ballpoint pen test. To help tell the species apart once you've found holes: try inserting the tip of a ballpoint pen. If only the very tip fits, it's likely a true powderpost beetle. If the tip and part of the pen body fits, probably deathwatch. If the whole pen tip fits easily, likely false powderpost.
- Frass texture test. Collect a small amount of the powder. Rub it between your fingers. If it feels as fine as talcum powder, it points to powderpost or deathwatch. If the frass is packed into the hole and difficult to dislodge, that suggests false powderpost (Bostrichidae).
- Active vs. old infestation. Fresh frass is pale and powdery. Old frass darkens over time. If the holes are dark and the frass is discoloured, the infestation may be old and no longer active — especially in very dry, well-maintained wood. That doesn't mean the damage isn't there; it just means treatment may be less urgent.
What I look at during an inspection: Sub-area framing, sill plates, and floor joists are my first stop. Then any exposed structural members in a basement or unfinished space. Hardwood floors with small unexplained holes, antique furniture, and any wood that's been stored or installed in a damp environment. Exit holes in wood that's been painted or finished are sometimes easier to spot — the clean round holes stand out against a flat painted surface.
Why moisture is the key variable
For both true powderpost beetles and deathwatch beetles, moisture content of the wood is the single biggest factor in whether an infestation can establish and spread. True powderpost beetles need moisture above about 8%; deathwatch beetles need above 14%.
This means that a well-ventilated, dry crawl space is significantly more resistant to beetle activity than a damp one. It also means that addressing a moisture problem — improving sub-area ventilation, fixing a grading issue that sends water toward the foundation, repairing a leaking pipe — is as important a part of the fix as treating the wood itself. Treat the beetles without addressing the moisture, and the conditions that invited them in the first place remain.
What they actually do to wood
The larvae are doing all the damage. Adult beetles mate and lay eggs in pores, cracks, or the end grain of susceptible wood. The eggs hatch, and the larvae spend months to years — the life cycle varies from a few months to over three years depending on species and conditions — tunnelling through the wood and eating it from the inside out. When they're ready to emerge as adults, they chew a round exit hole through the surface.
The result is a network of tunnels packed with frass, which steadily reduces the structural integrity of the wood. In flooring, you get soft spots and surface holes. In structural framing, a heavily infested joist or sill plate can lose a significant portion of its actual wood fibre — what looks like a solid beam from the outside can be mostly hollow inside. I've opened up framing in older sub-areas where the wood crumbles when you press it. That's an extreme case, but it happens.
Treatment options
The right approach depends on how extensive the infestation is, where it is, and whether it's still active. Here's what the options look like:
Remove and replace infested wood
Where it's feasible, removing and replacing heavily infested structural members is the most definitive fix. There's no ambiguity about whether the treatment worked. This is often the right call for badly damaged sill plates or joists in a crawl space, particularly if a moisture problem is also being corrected at the same time.
Borate treatments
Borate-based products (sodium borate — sold commercially as Tim-Bor, Bora-Care, and similar products) are the most commonly used treatment for wood-boring beetles in residential settings. Applied to bare, unfinished wood, the borate penetrates into the wood and kills larvae on contact. It also remains in the wood as a long-term preventive barrier.
The critical limitation: borate treatments only penetrate unfinished wood. Painted, stained, or sealed surfaces won't allow adequate penetration. This makes them very effective in unfinished sub-areas and framing, but not useful for finished hardwood floors or furniture without stripping the finish first. A licensed pest control professional is the right person for this application.
Heat treatment
Raising the core temperature of infested wood to around 55°C (133°F) and holding it there for 30 minutes kills beetles at all life stages. This is used for localized treatments of structural materials and for wooden packing materials. It's effective but requires specialized equipment and professional application.
Freezing
Small infested objects — furniture, wooden decorative items, antiques — can be treated by placing them in a deep freezer at −18°C (0°F) for at least 72 hours. For thicker pieces (over about 5 cm), a longer treatment period may be needed to ensure the cold penetrates to the core. This is a practical, low-cost option for isolated items and doesn't involve chemicals.
Fumigation
Whole-building fumigation is the option for widespread, inaccessible infestations — particularly deathwatch beetles in structural framing where borate penetration isn't possible. It's expensive, requires vacating the property, and should be carried out by a licensed pest control operator. If fumigation is recommended, a new active infestation should be treated promptly once the fumigant clears.
Prevention
Most beetle infestations in homes were introduced in infested wood before it arrived on site. The wood was already infested at the lumber yard, the millwork shop, or in the furniture warehouse. Prevention, therefore, starts before the wood comes through the door.
- Inspect firewood before bringing it inside. Firewood is one of the most common ways beetles are introduced into a home. Look for exit holes and frass before stacking wood in or near the house. Store firewood outside and away from the structure.
- Inspect antiques and used furniture before bringing them in. Check for small round holes and fine powder on or below the piece. A light tap can sometimes dislodge frass from active exit holes. When in doubt, isolate the piece until you can have it assessed.
- Use kiln-dried lumber. Kiln drying kills all life stages of wood-boring beetles. Lumber specified as kiln-dried (KD) is beetle-free at the time of milling — though it can be re-infested if stored improperly before use.
- Keep the sub-area dry and ventilated. Address any moisture issues in crawl spaces: proper vapour barriers, adequate cross-ventilation, and no standing water. Dry wood is resistant wood.
- Remove dead wood near the structure. Dead tree limbs, old stumps, and wood debris near the foundation can harbour populations that eventually find their way into the building.
What I note in an inspection report
When I find evidence of wood-boring beetle activity, I note the location, the type of evidence observed (exit holes, frass, damaged wood), and whether it appears active or historical. I'll recommend further assessment by a licensed pest control professional or structural engineer depending on the extent and location of the damage.
What I won't say is that the wood is "fine" or "not structurally compromised" based on appearance alone — the real damage is inside the wood, and a visual inspection has limits. If you're buying a home with a history of beetle activity, or a home where the evidence is ambiguous, a specialist's assessment is money well spent before you close.
Reference document: Wood-Boring Beetles in Homes (PDF) — from the University of California Statewide Integrated Pest Management Program. Covers identification, life cycles, diagnostic tests, and management options for powderpost, deathwatch, and false powderpost beetles.