Quick answer
A wood-boring insect is any insect that chews tunnels into wood to feed, nest or develop, including powderpost beetles, the old house borer, forest borers that emerge from new lumber, and some ants, bees and termites.
The key question for a homeowner is not whether an insect bores, but whether it can re-infest dry wood in a building. Many borers cannot, and their holes need no treatment.
Quick facts
The key facts about Wood-Boring Insect, with sources:
- Main beetle groups in homes
- Lyctid, anobiid and bostrichid powderpost beetles; old house borer 2
- Re-infest buildings
- Lyctids, anobiids, old house borer: yes; bostrichids: rarely 2
- Forest borers in new wood
- Emerge from new lumber but cannot re-infest it 1
- Old house borer larval time
- 2–3 years, up to 15 years in very dry wood 2
- Inspection form
- NPMA-33 for HUD/VA home sales 6
Key takeaways
- “Wood-boring insect” is a broad label covering beetles, termites, carpenter ants and carpenter bees.
- The beetles that matter most in homes are powderpost beetles and the old house borer, because they can re-infest dry wood.
- Forest borers that chew out of new framing or firewood usually cannot re-infest the house.
- Hole shape and size, frass texture and wood type point to the culprit.
- Fresh powder or live insects mean activity; old holes alone often need no treatment.
What counts as a wood-boring insect
Any insect that tunnels into wood is a wood borer. Most do it as larvae: a grub hatches inside the wood, eats for months or years, then chews out as an adult. That is why most borer damage is hidden until exit holes appear.
In homes, the beetles to know are the three powderpost beetle groups and the old house borer, a long-horned beetle 5/8 to 1 inch long 2. UMD Extension says the old house borer feeds mainly on softwood, especially pine, and mostly infests wood less than 10 years old, despite its name 3.
Another group comes from the forest. Roundheaded and flatheaded borers lay eggs in living or freshly cut trees. UC IPM notes they sometimes emerge from new wood in a house but cannot re-infest that wood 1.
Termites, carpenter ants and carpenter bees also tunnel in wood but are usually treated as their own categories. NPMA’s inspection form groups termites, carpenter ants, carpenter bees and re-infesting wood-boring beetles together as wood-destroying insects 6.
How wood-boring insects get into a house
Most borers arrive inside the wood itself, not through the door.
- Eggs laid in trees, logs or stored lumber
- Larvae tunnel inside while the wood is milled, dried and shipped
- Wood is built into framing, floors, trim or furniture
- Adults chew out months or years later, leaving exit holes and frass 1
- Re-infesting species lay new eggs in bare wood or old holes 2
- Egg in woodTree, log or lumber
- Hidden larvaMonths to years of feeding
- Built into homeFraming, flooring, furniture
- Exit holeAdult emerges, leaves frass
Whether the cycle repeats depends on the species and the wood’s moisture. Source: [1] [5]
Texas A&M says home lyctid infestations are almost always from wood infested before construction 5. Firewood is another route, which is why UC IPM advises bringing in only what you will burn that day 1.
Wood-boring beetles found in homes
| Insect | Wood | Exit hole | Re-infests? |
|---|---|---|---|
| Lyctid powderpost beetle | Hardwoods only 2 | Round, 1/32–1/16 in. 2 | Yes 2 |
| Anobiid (deathwatch) beetle | Hardwoods and softwoods; damp wood 2 | Round, 1/16–1/8 in. 2 | Yes 2 |
| Bostrichid (false powderpost) | Mostly freshly cut hardwoods 2 | Round, 3/32–9/32 in. 2 | Rarely 2 |
| Old house borer | Seasoned softwoods, especially pine 2 | Oval, 1/4–3/8 in. 23 | Yes 2 |
| Roundheaded and flatheaded forest borers | Living or freshly cut trees | Varies | No, cannot re-infest structural wood 1 |
Termites and carpenter ants have their own pages: see subterranean termite and carpenter ant.
Example: three holes, three different answers
This illustration applies extension guidance to three common finds. It is not a diagnosis.
| What you find | Likely insect | Usual next step |
|---|---|---|
| Oval 3/8-inch hole with ragged edges in a 5-year-old pine joist, fresh sawdust below | Old house borer 32 | Licensed inspection; UMD says fresh frass that returns after cleanup means activity 3 |
| Pinhead holes in an oak floor, talc-like powder | Lyctid powderpost beetle 12 | Check activity; replace or treat limited boards 5 |
| Large hole in new framing the first summer, no fresh powder later | Forest borer emerging from new wood | UC IPM says it cannot re-infest; usually no treatment 1 |
The same symptom, a hole in wood, leads to three different plans. Identification is worth more than any spray.
Where you will see the term
On a wood-destroying insect inspection report, usually the NPMA-33 form in home sales. The form reports visible evidence: live insects, dead insects, frass and damage 6.
On a treatment quote, the insect should be named. “Wood borers” alone is too vague, because the method depends on species.
On lumber and pallets, you may see a heat-treatment stamp. UC IPM notes the international standard for wood packing is heating the core to 133°F for 30 minutes 1.
On a home warranty or termite bond, check whether beetles are covered or only termites. Our page on termite warranties and bonds explains what to read.
Warning signs of wood-boring insects
- Round or oval exit holes in wood surfaces 13.
- Piles of powder or sawdust-like frass below holes 13.
- Frass that comes back a few weeks after cleanup, a sign of activity 3.
- Rasping or clicking sounds inside wood, most often in spring and summer for the old house borer 3.
- Beetles on windowsills, since many adults fly to light 1.
- Soft or blistered wood surfaces when probed 4.
Hidden damage and treatment safety
NC State notes infested wood can look sound on the surface; structural concerns may need a contractor or engineer 4.
Clemson says fumigation can only be done by a certified operator 2, and UC IPM says borates must be applied by a licensed one 1. Never try fumigation yourself.
Anyone exposed to a wood treatment product should call Poison Help at 1-800-222-1222.
What each control option does well
Strengths
Why wood borers are hard to deal with
Borers stay hidden for years. Old house borer larvae can take 2 to 5 years or more 3, and up to 15 years in very dry wood 2. By the time holes appear, the larvae have been feeding for years.
Signs can mislead. UMD notes a few adult beetles indoors does not by itself mean an infestation 3, and many holes are old. That makes over-treatment common.
Reaching the larvae is the third problem. They sit inside joists, sill plates and wall framing where surface products do not reach.
What drives the cost of wood-borer work
We do not publish prices, because fair figures need many dated local quotes. These factors move a quote.
Species and spread come first: a few boards versus framing across a house. Access matters: open crawl spaces are easier than finished walls. Method matters: wood replacement, borate, surface treatment or whole-structure fumigation. Structural repair by a contractor and crawl space moisture work can be separate costs.
See our pest control cost guide for how quotes are built, and the termite treatment cost estimator for drivers of a related wood-insect job.
On warranties: fumigation kills insects present but does not prevent new ones 1, so ask what a guarantee covers and for how long.
How a professional deals with wood borers
- Identify the insect from hole shape, size, frass and wood type.
- Decide if it re-infests. Forest borers from new wood usually need no treatment 1.
- Confirm activity. Clean frass and recheck in a few weeks 3.
- Check moisture in crawl spaces and framing 4.
- Remove and replace limited infested wood 3.
- Treat or fumigate widespread or hard-to-reach infestations, through a licensed company 32.
Structural repairs may need a local building permit. Pest work is done under a state license; see pest control licensing.
Preventing wood borer problems
- Keep crawl spaces dry with ventilation and a plastic ground cover over most of the soil 24.
- Seal bare wood with paint, varnish or polyurethane 2.
- Bring in only the firewood you will burn that day, and store the rest away from the house 1.
- Remove dead limbs and scrap lumber near buildings 1.
- Inspect used furniture and reclaimed lumber before bringing it inside.
Firewood is a common culprit
Beetles emerging indoors in winter often come from firewood stacked inside. UC IPM advises bringing in only what you will burn that day 1.
See our pages on moisture control and seasonal pest prevention.
When to call a professional
Call when fresh frass keeps returning, when oval holes appear in softwood framing, when you hear clicking in walls, or when a home sale inspection finds evidence.
Call a contractor or structural engineer too if joists or beams feel soft or sag 4.
For a visit that checks for termites, carpenter ants and beetles together, see our wood-destroying insect inspection service.
Rules and standards that apply
NPMA-33. The NPMA-33 must be used for wood-destroying insect inspections on HUD/VA guaranteed property transactions; where a state requires its own form and excludes others, the state form must be used. Findings are limited to visible evidence 6.
Pesticides (EPA, FIFRA). Wood treatments are EPA-registered pesticides and must follow the label. UC IPM says borate products must be applied by a licensed operator 1.
Fumigation. Clemson notes fumigation must be done by a certified operator 2; states license fumigation as its own category.
Wood packing. International phytosanitary rules require heat treatment of wood packing; UC IPM gives a core temperature of 133°F for 30 minutes 1.
Wood-boring beetles vs other wood-damaging pests
| Pest | Main sign | Notes |
|---|---|---|
| Wood-boring beetles | Round or oval exit holes, frass 1 | Some re-infest, some do not 2 |
| Drywood termites | Pellets larger than anobiid frass 1 | Live inside dry wood |
| Carpenter bees | Round holes in exposed wood, staining | Listed on NPMA-33 6 |
| Wood decay fungi | Soft, cracked or stringy wood | NC State: decay stops below 20% moisture 4 |
Moisture links most of these. Dry wood resists both insects and decay.
Common wood-borer myths
- Myth Any beetle hole means treatment.
- Reality Forest borers from new wood cannot re-infest 1, and old damage without fresh powder needs no treatment 2.
- Myth The old house borer only attacks old houses.
- Reality UMD says it mostly infests wood less than 10 years old 3.
- Myth A few beetles inside means an infestation.
- Reality UMD says a few adults indoors does not by itself mean one 3.
- Myth Fumigation protects wood for the future.
- Reality It does not prevent reinfestation 1.
- Myth Kiln-dried lumber is borer-proof.
- Reality Kiln drying kills insects but does not prevent reinfestation 1.
Where climate and state rules change the picture
Moisture is the regional driver. NC State says anobiid beetles are the main wood-boring concern in North Carolina crawl spaces, where pine and fir joists stay damp 4, and Clemson says old house borer larvae develop best in wood at 15–25% moisture 2.
Dry, slab-built homes see fewer of these. Paperwork varies too: NPMA says a state-mandated inspection form must be used where a state requires one 6. Ask your inspector which form your state uses.
When it matters to you, and what to do next
A simple rule covers most cases. Holes in new framing that never show fresh frass: likely forest borers, monitor only. Fresh frass in hardwood floors or furniture: powderpost beetles, replace or treat pieces. Oval holes and fresh frass in softwood framing, or clicking in walls: get a licensed inspection.
Keeping wood dry is the single step that helps against beetles, termites and decay at once.
When hiring, ask the company to name the insect, show the evidence of activity and explain why a treatment is needed. Our guide to choosing a pest control company has more questions.
Quick decision guide
Old holes with no fresh frass can be monitored. Fresh frass in movable wood calls for replacing or treating it. Fresh frass or clicking in framing needs a licensed inspection, and soft joists need a contractor too.
Questions about Wood-Boring Insect
What is a wood-boring insect?
A wood-boring insect is any insect that tunnels into wood to feed, nest or develop. In homes, that mainly means powderpost beetles and the old house borer, plus forest borers that emerge from new lumber. Termites, carpenter ants and carpenter bees also bore into wood but are usually treated separately.
How do I know which wood borer I have?
Look at the hole, the frass and the wood. Clemson says lyctid holes are round and 1/32 to 1/16 inch in hardwood, anobiid holes 1/16 to 1/8 inch, and old house borer holes oval and 1/4 to 3/8 inch in softwood. Fine talc-like powder points to lyctids; sawdust-like frass to larger borers.
Do I need to treat beetle holes in new framing?
Often not. UC IPM says roundheaded and flatheaded forest borers sometimes emerge from new wood but cannot re-infest it. If holes appear in the first year and no fresh frass follows, treatment is usually unnecessary. Have an inspector confirm the species first.
What is an old house borer?
The old house borer is a long-horned beetle, 5/8 to 1 inch long, whose larvae tunnel in seasoned softwood, especially pine. Despite the name, UMD says it mostly infests wood less than 10 years old. Its exit holes are oval, 1/4 to 3/8 inch, often with ragged edges.
Can you hear wood-boring insects?
Sometimes. UMD says large old house borer larvae make rasping or clicking sounds, most likely in spring and summer when wood moisture is higher. UC IPM notes deathwatch beetle adults tap their heads against wood, usually at night. Sound is a clue, not proof; confirm with fresh frass.
How long do wood-boring insects live inside wood?
It varies a lot. Clemson says lyctid life cycles take 9 to 12 months, anobiids usually 2 to 3 years, and old house borer larvae 2 to 3 years, or up to 15 years in very dry wood. That is why damage can show up years after a house is built.
Are wood-boring insects dangerous to my house?
Some can be. Re-infesting species like anobiids and the old house borer can weaken framing over many years if left alone. Others, like forest borers in new lumber, do minor damage and stop. NC State notes wood can look sound outside, so have structural wood checked if signs are fresh.
Can firewood bring wood borers into my house?
Yes. Beetles in firewood can emerge indoors, especially in heated rooms. UC IPM advises bringing in only the firewood you will burn that day and removing dead limbs and scrap lumber near buildings. Most firewood beetles cannot infest dry house wood, but some can.
How are wood-boring insects treated?
It depends on the species and spread. Limited damage is usually fixed by replacing the wood. Borates and labeled insecticides can be used on bare wood by licensed operators. Widespread or hidden infestations may need fumigation by a certified operator, which does not prevent future infestations.
Will a home inspection catch wood borers?
A wood-destroying insect inspection should report visible evidence. The NPMA-33 form, required for HUD/VA home sales, covers termites, carpenter ants, carpenter bees and re-infesting wood-boring beetles. Findings are limited to visible areas, so hidden damage can still exist.
Sources
- UC Statewide IPM Program, Pest Notes: Wood-Boring Beetles in Homes (Publication 7418), retrieved .
- Clemson Cooperative Extension HGIC, Wood-Boring Beetles in Houses (Factsheet 2417), retrieved .
- University of Maryland Extension, Old House Borer, retrieved .
- NC State Extension, Powderpost Beetles and Wood-Inhabiting Fungi, retrieved .
- Texas A&M AgriLife Extension, Lyctid Powderpost Beetles: Suggestions for Control, retrieved .
- National Pest Management Association, Suggested Guidelines for Completing the NPMA-33 (v1.3, 2019), retrieved .
Expert review
Written by the HyrePest Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Beetle group traits, hole sizes, moisture ranges, life cycles and reinfestation are from Clemson HGIC 2417 and UC IPM Pest Notes 7418. Old house borer details are from UMD Extension.
Moisture and crawl space guidance are from NC State; infestation origin and treatment limits from Texas A&M AgriLife. Inspection rules are from NPMA’s 2019 NPMA-33 guidelines.
Suggest a correction. We fix errors and say what changed.