Furniture Beetle & Borer in Antique Furniture: What NZ Owners Need to Know

Borer is the question I get more than almost any other, usually with a photo of a piece full of small round holes and a message that says "is this a write-off?" Almost always, the answer is no. Borer is common in New Zealand — our climate and our love of old rimu, kauri and villa-era furniture make it almost unavoidable. It's manageable if you know what you're looking at.

After handling thousands of pieces, most with borer holes somewhere, here's what I actually check and what I'd tell a friend.

What Furniture Beetle & Borer Actually Are

"Borer" is the general NZ term for wood-boring beetle larvae that tunnel through timber, feeding on it from the inside, then emerge as adult beetles through small exit holes — that's what you're seeing on the surface. The tunnelling inside the timber is the actual damage; the holes are just where the beetle left.

Active vs Old Borer: The Key Tell

This is the single most useful thing to know, and most people never check it.

• Frass is the tell. Frass is the fine, powdery wood dust the larvae push out as they tunnel. If you see pale, fresh-looking dust around or under a hole, or dust that reappears after you've wiped it away, that's a sign of active borer.
• Old, inactive holes are usually darker, slightly weathered-looking inside, with no dust present and none returning after cleaning. Many antique pieces have old exit holes from decades ago with no ongoing activity at all.
• Do the wipe-and-wait test. Clean all visible holes and the surrounding area properly, then check back over a few weeks. New dust means it's active. No dust means it's most likely old damage.
• Tap and press test. Gently press a screwdriver or awl into the timber near the holes. Solid resistance is good. If it sinks in easily or the wood feels soft and crumbly underneath, the internal damage is more extensive than the surface suggests.

Is a Piece With Borer Worth Buying or Restoring?

Almost always, yes — with a few sensible checks first.

• Scattered old holes on solid, structurally sound timber are cosmetic. They don't affect the piece's usability and can even be part of its character. I wouldn't walk away from a good piece for this alone.
• Heavy clusters of holes concentrated in one area, especially on structural elements like chair legs, table frames or joints, are worth a closer look — that's where strength actually matters.
• Soft, crumbly, or hollow-sounding timber is the real red flag, not the holes themselves. That tells you the internal structure has been compromised, not just cosmetically marked.
• Price it accordingly. Borer damage, even active, is very often treatable and shouldn't scare off a fair offer — it should just factor into what you're willing to pay.

Basic Treatment Options

For most furniture-scale borer, treatment is straightforward and something a confident DIYer can manage:

• Borer treatment fluid, applied to the affected timber and worked into the exit holes, is the standard approach for common household-scale infestations. Follow the product instructions carefully, work in good ventilation, and treat the whole piece, not just the visible holes.
• Repeat treatment is often needed, since larvae can be tunnelling well below the surface. Check back over the following months for any fresh frass.
• Isolate the piece while treating. Keep it away from direct contact with other timber furniture until you're confident the activity has stopped.

For serious infestations — large areas of soft or collapsing timber, activity across multiple pieces, or any doubt about a piece's structural integrity — it's worth getting a professional pest assessment. A pest control professional can confirm the extent of an infestation and recommend proper treatment, particularly for anything approaching structural timber in a home rather than a single piece of furniture.

Once any active infestation is treated, repairing the affected timber — a replaced panel, a re-glued joint — is exactly the kind of job our restoration service can take on if you'd rather not do it yourself.

Preventing It Spreading to Other Pieces

• Quarantine new finds. Keep anything you're unsure about away from the rest of your furniture until you've done the wipe-and-wait check.
• Keep humidity down. Borer and general timber pests are more active in damp, poorly ventilated spaces — garages, sheds, and closed-up rooms. Good airflow makes your whole collection less hospitable.
• Check regularly. A quick visual check every few months on older pieces, especially ones stored in garages or basements, catches new activity early.
• Treat, don't ignore. If you find active frass, treat that piece before bringing anything new into the same space.

Borer is one of those things that looks alarming and usually isn't. Most of what I see is old, inactive, and purely cosmetic. Learn the frass test, price sensibly for what you actually find, and don't let a handful of small holes talk you out of a genuinely good piece. If you want a broader walkthrough on separating cosmetic issues from real structural problems before you buy, that's covered in our Dirt or Damage guide.

Related Reading

• Dirt or Damage: How to Tell Before You Buy
• Furniture Restoration in Auckland
• Is It Worth Restoring? An Assessment Guide
• The Treasured Legacy of New Zealand Rimu Furniture