Does kerosene kill borer? (and turps, and fly spray)
Three things most garages already have, tested against how borer lives in timber.
Facts and prices checked 5 November 2026
Kerosene can kill a borer larva it soaks into directly, but it doesn't stop an infestation. It evaporates, leaves no lasting protection, and most larvae sit too deep for it to reach. Turpentine behaves the same way, and fly spray only kills an adult beetle you happen to hit. This answer belongs to our guide on homemade borer treatments, part of borer treatment in Auckland.
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Why do people use kerosene on borer?
People use kerosene on borer because it's an old habit, it's cheap, and it does soak into dry timber. Older generations brushed it onto floorboards and furniture, and some borer treatments really were mixed with it. The habit stuck even though the kerosene was mostly the carrier, not the part doing the killing.
That carrier role still exists. One manufacturer's borer concentrate can be diluted with kerosene instead of water, and its directions note the smell lasts for days when you do. The active ingredient in that product is permethrin, an insecticide. Kerosene on its own has none.
Does kerosene kill borer larvae?
Kerosene kills a borer larva only if enough of it reaches the larva in its tunnel. Brushed on the surface, it soaks into the outer wood and then evaporates. Larvae deeper in the timber are untouched, and the next eggs land on wood with nothing left to stop them. Borer larvae can live inside timber for up to about four years, so a treatment that lasts days misses almost all of them.
| What you use | Reaches larvae deep in the wood? | Leaves lasting protection? | Main risk |
|---|---|---|---|
| Kerosene, brushed on | Barely | No | Flammable, strong fumes indoors |
| Kerosene, squirted into holes | Some, near the holes | No | Flammable, stains finishes |
| Turpentine | Barely | No | Flammable, fumes |
| Fly spray | No | No | Sprays insecticide into living spaces |
| Residual borer treatment on bare timber | Catches each new generation | Yes, for years | Follow the label |
| Borer injector in flight holes | Yes, in finished timber | Yes | Follow the label |
Does turpentine kill borer?
Turpentine doesn't kill borer any better than kerosene. It's a solvent, it evaporates, and it leaves nothing behind to stop the next generation. It can kill a larva it soaks into directly, and that's all. Like kerosene, it's flammable and gives off fumes, so it's a poor choice on floors, framing or furniture inside a lived-in house.
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Does fly spray kill borer?
Fly spray kills an adult borer beetle if you spray it directly, but it does nothing to the larvae in the wood. The adults you see near windows are already on their way out, and many have laid eggs. Fly spray is made to be sprayed into the air, not to soak into timber, so it leaves no protection on the surface either.
Seeing beetles near a window is still useful information. It tells you the borer is active somewhere nearby, during the flight season, and that's the time to treat the bare timber properly.
What should you use instead?
Use a product made for borer: a residual treatment brushed or sprayed onto bare timber, and an injector for flight holes in painted or varnished wood. The residual treatment stays on the surface for years, so each new generation of adults and eggs meets it. Fix damp at the same time, because borer favours timber with some moisture in it.
The order that works for a DIY job:
- Confirm the borer is active. Fresh, pale holes and new dust after cleaning are the signs.
- Strip finish where you can, because a surface treatment only works on bare wood.
- Apply a residual borer treatment, two coats if the label says so, and keep children and pets away until it's dry.
- Inject flight holes in painted or polished timber.
- Check again next flight season for new holes.
Our page on how to treat borer covers each step, and the product safety notice covers the precautions.
Questions people ask
Is kerosene safe to use on borer inside the house?
Kerosene isn't a good choice inside a lived-in house. It's flammable, the fumes linger for days, and it can stain finishes and soft furnishings. It also doesn't protect the timber once it evaporates. A water-based borer treatment made for indoor timber avoids most of those problems.
Does diesel or petrol kill borer?
Diesel and petrol have the same problems as kerosene, and worse. They're flammable, smelly and harmful to breathe, and they leave no useful protection. Neither is a borer treatment. Don't use either on house timber or furniture.
Can I mix my own borer treatment with kerosene?
Only if the product's label says so. At least one borer concentrate sold in New Zealand allows kerosene as the diluent instead of water, for longer-lasting protection, but warns that the smell stays for days. The insecticide in the concentrate does the work. Kerosene by itself isn't a borer treatment.
Will fly spray stop borer coming back?
No. Fly spray kills the beetle you hit and nothing else. It doesn't soak into the wood or stay on the surface, so the larvae keep feeding and the next generation comes out on schedule. A residual borer treatment on bare timber is what stops it coming back.