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When and How to Protect Your Home from Borer

Posted in Pest Advice on September 20, 2021

When to Protect Your Largest Investment - Your Home 

Your largest investment is likely to be your home, what if something was eating its way through your house?

There are maybe 7 species of wood-boring insect in New Zealand that attack the timbers of homes or other buildings. The most common of these is the Common House Borer (Anobium punctatum) also known as Woodworm and Furniture Beetle. A close relative is the New Zealand Native House Borer (Leanobium flavomaculatum). It is rarely distinguished from the Common Borer and may, in fact, be the more common. Both prefer to eat softer sapwood timber and don’t attack harder heartwood timbers. It is common to see many borer holes in a part of a weatherboard and not other parts; the attacked part will be the softer sapwood.

The life cycles of these insects are similar. Adult females lay up to 100 eggs on bare timber or in old flight holes. The eggs hatch after 4-5 weeks and the larvae bore through the wood, eating it and using yeasts in their stomachs to help break down cellulose in the wood. After 3-4 years the larvae will pupate in a chamber near the surface, then 4-8 weeks later the adult beetle exits the wood by eating its way to the surface creating a 'flight hole'. The adults mate and begin the life cycle over again. The flight holes are approximately 2 mm in diameter for Common Borer and 3-4 mm for native borer.

The two-toothed borer longhorn (Ambeodontus tristis) is larger but less numerous than the common and native borer above. But it can be a real concern in house timbers as its larvae will attack heart wood structural timbers and the larger holes they create can do more damage.


It is important that a thorough check of the timbers in your home is carried out to determine the extent of any infestation. It is frequently the case that a few flight holes are visible on the exterior of painted weatherboards, however, when the boards are examined more closely the interior of the timbers are badly damaged and many flight holes are present on the interior surface. Borer are more inclined to exit in dark spaces than on surfaces in light.

Treatment of timbers to remove borer infestation is the same for whichever species is present.

Treat the Wood (Any Time)

Direct treatment of wood is the best method of protection and can be applied at any time of the year. Treat any bare wood with Kiwicare NO Borer Total Wood Protection fluid. This oil-based timber treatment will penetrate deep into the timber and will kill borer larvae as they eat the wood and prevent adults from laying eggs on the surface. In normal circumstances, this will protect the wood for many years.

Inject flight holes with Kiwicare NO Borer Injection fluid. This comes in a handy aerosol supplied with a nozzle for fitting into the holes. The aerosol forces insecticide into the labyrinth created by the borer larva killing any larva in the labyrinth or nearby. It also prevents adult beetles from laying eggs in the flight hole.

Bomb the Borer (October-March)

During each flight season (October-May) set off Kiwicare NO Bugs Super Fumigator ‘borer bombs’ in living spaces, roof voids and sub-floor areas. These knockdown adult beetles that would lay eggs on the exposed timbers and give protection to the surface of the timbers.

Dry the Wood (All the Time)

Borer prefer timber that has some moisture in it. Ensure that your sub-floor is dry and well ventilated. Check for plumbing leaks and unblock all air vents. Check for leaks in the roof and if you have old terracotta or concrete tiles check that they are in good order. Unsealed these can act like sponges soaking up water and increasing the relative humidity of roof voids. Ensure tiles are sealed and not allowing water penetration.

This combination of treatment will protect your home and your investment for many more years.

For more information read the 1-2-3 Borer Control Programme.

David Brittain

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