Furniture
Borer in furniture, and how to keep the piece
How to tell whether borer in a chair, dresser or antique is still active, which beetle made the holes, and how injection, freezing and refinishing deal with it.
The short answer
Borer in furniture is usually treatable without losing the piece. First establish that it is live, from fresh pale dust and clean holes, because many old pieces carry holes from decades ago. Then match the method to the finish: bare timber takes a surface or borate treatment, polished and painted timber is injected hole by hole, and small items can be frozen. Large or valuable pieces, or a house full of them, warrant professional borer treatment.
At a glance
Matching the method to the piece
| Part of the piece | Usual finish | What reaches the borer | Watch for |
|---|---|---|---|
| Back panel, underside, drawer bottoms | Bare, unfinished timber | Residual or borate product brushed on | This is where borer usually starts |
| Polished or varnished faces | Shellac, varnish, oil, wax | Injector into each flight hole | Some products mark polish; test hidden first |
| Painted pieces | Paint | Injector into each flight hole | Fill holes only after treatment |
| Small items: frames, boxes, carvings | Any | Freezing at about minus 20 °C for a week | Inlays and mother-of-pearl can be affected |
| Antiques and veneered pieces | Original finish | Ask a furniture restorer first | Liquids can lift veneer and mark the finish |
Which borer is in the furniture?
The timber tells you. Pine, rimu and kahikatea furniture, which covers most colonial and mid-century New Zealand pieces, is attacked by the common house borer, Anobium punctatum, which leaves round holes of 1–2 mm and gritty dust. Oak, ash, elm and tawa pieces can carry the powderpost beetle instead, with smaller holes and dust as fine as talc, and only in the sapwood, the paler wood near the edge of a board.
The difference changes what you do next. Powderpost infestations almost always arrive in timber that was infested before it was made up, often imported hardwood, so holes appearing in a fairly new oak or ash piece point back at the maker or the seller rather than at your house. The common house borer is different: it can move between untreated pieces and the untreated timber of an older house, in either direction, which is why a live piece should not sit untreated beside a rimu sideboard.
How do you get rid of borer in furniture?
By the finish. Bare surfaces, the back panel, the underside, the drawer runners and the inner faces of the cabinet, take a residual or borate treatment brushed on, and those unfinished parts are where borer usually starts. Finished faces are treated through the holes with an injector, working every hole and then sealing it. If new holes appear after the next flight season, repeat on those.
Take the drawers out and treat the runners and the drawer bottoms separately, since they are almost always bare. Test any product on a hidden spot first, because some mark French polish and shellac. With antiques, veneered pieces or anything you would be upset to see marked, ask a furniture restorer for advice before any liquid goes near it. We have compared what injectors and sprays can and cannot reach if you are choosing a product.
Can you freeze borer out of furniture?
For smaller pieces, yes. Seal the item in plastic, hold it at about minus 20 °C for seven days, then let it warm slowly to room temperature before unwrapping, so condensation forms on the bag rather than on the wood. University of Kentucky entomologists describe this as killing every stage inside, eggs included, with no chemicals, but it leaves no protection behind, so treat or seal the bare surfaces afterwards.
It needs a freezer that genuinely holds minus 20 °C. Many home freezers do; check yours with a thermometer before relying on it, and for anything too big, ask a cold storage business. Inlays and mother-of-pearl can be affected by the cold, and ordinary veneers and finishes usually come through well. Heat is not the alternative it might seem, since it is not recommended for glued items. Furniture can also be fumigated, but that is work for a licensed fumigator and not a service we offer.
Bringing second-hand furniture home
Check a piece before it comes inside. Turn it over and look at the unfinished back, the underside and the drawer bottoms for holes and dust, then tap it firmly over a sheet of dark paper and see what falls out. If anything looks fresh and pale, keep the piece in the garage and treat or freeze it first. A live infestation in untreated furniture is one of the ways borer reaches a house.
Old holes with no dust are common in auction and online marketplace furniture, and they are not a reason to walk away. Ask the seller where the piece has been kept and whether anyone has seen fresh dust under it, and look closely at the joints and the feet, where dust collects. Bought in winter, a live piece may look quiet until its first summer indoors, which is when to look again.
Questions
Questions about borer in furniture
How long do woodworm live in furniture?
Woodworm is the larva of the common house borer, the beetle the British call the furniture beetle. It spends three to four years in the sapwood before emerging as a beetle that lives only a few weeks, and in a dry, heated room development can be slower still. So a piece can keep producing new holes for several years after it was last exposed to egg-laying beetles.
Will borer in my furniture spread to the house?
Only if the furniture has unfinished, untreated timber and the infestation is live. Beetles emerge in early summer and lay in bare wood or in old holes close by, while finished surfaces are generally safe from egg-laying. Treating or freezing the piece, then sealing its bare surfaces and filling the holes, takes away the risk to anything else in the room.
Can I fill borer holes in furniture?
Yes, once the borer is dead or the piece has been treated. Coloured wax or filler restores the look and stops beetles laying in their own exit holes. Fill the holes before treatment, though, and you hide the evidence of whether new holes are appearing, while the next generation will chew out through the filler anyway when it emerges.
Is an old piece with borer holes still worth keeping?
Usually. Historic holes are common in old New Zealand furniture and do not ruin it, and a piece with live borer can be treated before it joins the rest of your furniture. Questions about what a particular piece is worth belong with a dealer or a restorer rather than with us.
If you need someone
For a house full of it
More advice
Other things worth knowing
Is the borer in your house still active?
Most older Auckland houses have borer holes. How to tell live borer from old damage by the dust and the hole edges, and what it means if you are buying one.
Read this DIY treatmentTreating borer yourself, and what each product actually reaches
What borer bombs, surface sprays, hole injectors and home remedies such as vinegar or kerosene can reach inside timber, and when treating borer yourself is enough.
Read this Timber pestsBorer or termites?
Borer and termites both hollow out timber, but the dust, the holes and the next step differ. How to tell them apart in a New Zealand house, and when to call MPI.
Read thisNot sure what you are dealing with?
Describe it, or send a photograph. Identifying it correctly is our job, and it is what decides the treatment.