Borers are beetles that lay their eggs on timber. The eggs hatch and the pupae burrow their way into untreated wood. The larvae live in the wood, continuing to eat and tunnel their way through until they reach the adult beetle stage of their metamorphosis. At that stage, they burrow to the surface of the timber and fly out. They leave behind a neat little round or oval hole. Often fine or gritty sawdust will come out of the exit hole, called frass.

The tunnels weaken the timber and the 2 to 3 mm exit holes affect the appearance of the wood. They can attack untreated furniture or the timber structures in a house, including floorboards, joists and weatherboards.

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What do borers look like?

There are seven wood borer species in New Zealand. But the most common pest is an introduced species called the House Borer (Anobium punctatum).

House Borers are tiny beetles, only 3 to 4 millimetres long. They have a cylindrical red to brown coloured body with a hood over their thorax and head. The antenna is about a third of their body’s length and has three flattened segments at the end.

The larvae are a curved, white grub slightly bigger than the beetle, at about 7mm in length. The first eight segments have folds and the head is yellow with powerful jaws to chew through the wood.

What are the signs of active borer?

Exit holes and frass are signs you may have borer activity. The beetles like to emerge from timber in low light. So, look for holes under or behind furniture. Check the subfloor or any other places where the light doesn’t hit the wood.

In extreme cases, the tunnels, also called ‘galleries’, weaken the wood causing it to break. Dead beetles or crumbling corners around the wood edges are also sure signs you have a problem.

Eggs may be hard to spot, even though females can lay up to 100 eggs. They love untreated, rough sawn surfaces but will also lay eggs in old exit holes or crevices.

Adult beetles emerge in the warmer months and are airborne for about four weeks between November and March.

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How to prevent wood borers

Wood borers are attracted to damp wood, such as under the house. To prevent borers, make sure all leaks are sealed and the area is well ventilated. Don’t store material under the house, which can prevent air flow.

The southern side of buildings gets less sunlight, so are also more prone to borer attack. Keep an eye out for exist holes, especially if the timber stays damp on this side of the house.

If you purchase antique or second hand furniture, check for exist holes before bringing it home as it could introduce borers to your house.

The best preventative for borers is to paint or treat the wood.

Borer treatment

Furniture can be sealed and fumigated. Injecting the exit holes with an insecticide can also work. But fumigation in a house will only treat the flying beetles, not the larvae in the wood. If the damage is extensive, it may be best to remove the wood and replace it, as borers weaken the wood from the inside.

Your technician may apply a wood preservative to the timber. It is also a fungicide and insecticide and has no smell. Unlike many other insecticides, it lasts a long time in the timber and won’t break down. This means the beetle is treated before emerging from the wood.

Wood borers can cause severe structural damage to your home and economic loss. If you suspect you have wood borers, call us today for a free site inspection.

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