Tiny holes in wood are almost always exit holes left by wood-boring beetles. The adult beetles chew their way out after spending months or even years as larvae feeding inside the wood. The size of the holes, the type of dust around them, and where you found them can tell you exactly which insect is responsible and whether the infestation is still active.
What’s Making the Holes
The most common culprits are powderpost beetles, a group that includes several species with slightly different habits. They leave small, perfectly round holes in the wood surface, often described as “shot holes.” You’ll typically notice them alongside fine powder (called frass) that the beetles push out as they emerge. Less commonly, drywood termites create tiny holes in wood, but their holes look and behave differently from beetle damage.
The good news: not every hole means you have a live problem. Some wood arrives with old holes from beetles that were killed during kiln-drying or milling. Reclaimed wood and antique furniture often have cosmetic holes with no active insects behind them. The key is figuring out whether something is still living inside.
Identifying the Insect by Hole Size and Dust
You can narrow down the species by measuring the holes and examining the powder around them. A magnifying glass and a toothpick are all you need.
- Pinhead-sized holes with flour-fine powder: Lyctid powderpost beetles. Their exit holes are roughly 1/32 to 1/16 inch across. The dust feels like talcum powder or baking flour, and it often collects in small piles beneath or beside the holes. These beetles target hardwoods like oak, ash, and walnut.
- 1/8 to 1/4 inch holes with coarser, packed powder: Bostrichid powderpost beetles. Their dust has a more meal-like texture and tends to stay tightly packed inside the holes and tunnels rather than spilling out. Female bostrichids also bore directly into wood to lay eggs, leaving holes with no powder at all.
- 1/16 to 1/8 inch holes with gritty powder: Anobiid powderpost beetles, which include the common furniture beetle. Rub the dust between your fingers. If it feels slightly gritty, like fine sand mixed with powder, you’re likely dealing with anobiids. These beetles are more common in softwoods and in damp environments like crawlspaces.
- 1/16 inch holes with no powder, but tiny pellets nearby: Drywood termites. Their “kickout holes” are about 1/16 inch in diameter, and they push out fecal pellets rather than dust. The pellets are distinctive: roughly 1/32 inch long, six-sided, blunt on one end and pointed on the other. If you tap the wood gently, more pellets may fall out. Finding pellets shaped like this is a sure sign of drywood termites.
Active Infestation vs. Old Damage
This is the most important distinction. Old holes in otherwise sound wood don’t require treatment. Active infestations do, and they’ll get worse over time as new generations of beetles hatch and re-infest the same wood.
Fresh exit holes have a light-colored interior. Poke a toothpick into a hole: if the inside looks clean and pale compared to the weathered wood surface, the hole is recent. Old holes darken over time as they oxidize. Fresh frass is another reliable sign. Powder that’s light in color and loose, streaming from holes or collecting on surfaces below, points to beetles that are actively emerging. Frass that looks yellow and caked is old and typically means the infestation has run its course.
The simplest test is to seal or vacuum all existing holes and powder, then check back in a few weeks. New powder appearing on a clean surface confirms live activity. Peak emergence for most wood-boring beetles runs from May through August, but in heated buildings you can find new holes year-round.
How to Treat Active Infestations
Treatment depends on what’s infested. A single piece of furniture is a very different problem from structural framing in a crawlspace.
Small Items and Furniture
Heat is the most reliable non-chemical option. Raising the wood’s core temperature to 60°C (140°F) and holding it there for 30 minutes kills all wood-boring larvae. USDA research found that the commonly cited standard of 56°C left some borers alive, but bumping the temperature to 60°C achieved complete kill. For small items, a heated chamber or even a car parked in direct summer sun (monitored with a probe thermometer) can work. Freezing also kills larvae, but requires sustained temperatures below -20°C for several days, which typically means a commercial chest freezer.
Structural Wood and Large Areas
Borate-based wood preservatives are the standard treatment for larger infestations. These products use a boron compound that penetrates the wood and kills larvae when they feed. For dry wood, two coats of a 10% solution applied by brush or spray is the typical approach. Wood with normal moisture content gets one heavier coat at a 15% concentration. For deeper penetration into heavily infested timbers, you can drill small holes and inject the solution directly into the wood. Coverage runs about 5 gallons of mixed solution per 1,000 square feet. Borates are low-toxicity for people and pets, and they also protect against future infestations as long as the wood stays dry.
Drywood termite infestations in structural wood often require professional fumigation, especially if the colony has spread through multiple areas. Spot treatments with borates or localized heat can work for isolated pockets.
Preventing Reinfestation
Moisture is the single biggest factor. Wood-boring beetles, especially anobiids, need a certain moisture level in the wood to survive and reproduce. Keeping wood dry, through proper ventilation, dehumidifiers in basements and crawlspaces, and fixing leaks, makes it inhospitable. Kiln-dried lumber is far less vulnerable than air-dried wood because the drying process kills any existing larvae and reduces moisture to levels most beetles can’t tolerate.
Sealing or finishing wood with paint, varnish, or polyurethane also helps. Female beetles can’t lay eggs on sealed surfaces, and emerging adults can’t re-infest treated wood. Unfinished wood in humid environments is the highest-risk scenario. If you’re bringing reclaimed wood or antique furniture into your home, inspect it carefully before it comes inside. Look for fresh frass, light-colored hole interiors, and any loose powder that suggests recent activity.