How to get rid of borers in wood

Timber is one of New Zealand’s most valued building materials. It gives homes warmth, strength, and character — from polished floorboards and ceiling beams to treasured furniture. Yet this prized material is highly vulnerable to one of the country’s most destructive pests: borers.

Borers live inside wood, quietly eating away at its strength for years before leaving small exit holes and powdery dust. By the time you notice the signs, severe damage may already have been done. Left untreated, borers can weaken structural timber, damage antiques, and reduce property value.

This guide explains how to identify borer activity, why they’re a problem in New Zealand, and the most effective ways to get rid of them. We’ll also look at prevention strategies and the importance of professional treatment.

What are borers?

Borers are the wood-eating larvae of beetles. In New Zealand, several species attack both native and introduced timbers:

• Common Furniture Beetle (Anobium punctatum): One of the most widespread species, often found in softwoods used for flooring, furniture, and wall linings.
   
• Native House Borer (Leanobium flavomaculatum): Attacks both hardwoods and softwoods, particularly in older homes.
   
• Two-Toothed Longhorn Borer (Ambeodontus tristis): A larger species known for damaging structural timber, including beams and joists.

The beetle life cycle is the reason infestations are so destructive. Adult beetles lay eggs on or in cracks of timber. When the larvae hatch, they burrow inside the wood, feeding for three to seven years. During this time, they remain hidden, tunnelling deep into the timber. Eventually, they pupate and emerge as adult beetles, leaving small, round exit holes on the surface.

Because the larvae spend most of their lives inside the wood, infestations often go unnoticed until significant damage has already occurred.

Signs of a borer infestation

Spotting borers early is crucial for preventing significant damage. Some of the key indicators include:

• Exit holes: Small round holes, usually 1–2 mm wide, appear when adult beetles emerge. These are commonly seen in floorboards, skirting boards, and furniture.
   
• Frass (wood dust): Fine powder, often compared to sawdust, may be found near affected timber. Fresh frass around holes usually indicates active infestation.
   
• Weak or crumbling timber: Wood may feel soft, break easily, or sound hollow when tapped. In severe cases, floorboards may sag or collapse under pressure.
   
• Beetle sightings: Adult beetles may appear inside the house, especially in warmer months when they emerge to mate.

A professional inspection can help determine whether exit holes are old or part of an active infestation.

Why borers are a problem in New Zealand

New Zealand’s climate creates ideal conditions for borers. The combination of mild temperatures and damp conditions allows larvae to thrive inside timber. Older houses are particularly at risk, as many were built with untreated native timbers before chemical treatment became common.

Unchecked, borers can cause:

• Structural weakness: Joists, beams, and flooring can lose their strength, leading to sagging floors and safety hazards.
   
• Furniture damage: Antique and valuable furniture is especially vulnerable, with damage often impossible to repair.
   
• Financial costs: Repairing or replacing timber can be expensive, especially when structural components are affected.
   
• Ongoing infestations: Borers can spread to multiple areas of a property, making treatment more difficult over time.

Given the hidden nature of the damage, borers represent one of the most costly long-term pest issues in New Zealand homes and buildings.

How to get rid of borers in wood

Getting rid of borers is not as simple as treating the surface of the wood. Because larvae live deep inside, effective control requires treatments that penetrate timber and break the beetle life cycle.

1. Professional inspection

The first step is identifying the species and assessing the scale of infestation. A licensed pest control expert can determine whether holes are active and recommend the best treatment. Inspections often include checking underfloor areas, attics, and roof timbers that aren’t easily visible.

2. Replacing damaged timber

In cases where wood has been badly weakened, replacement may be necessary. Structural elements like beams and floor joists cannot always be saved if heavily infested. Replacing damaged timber ensures safety and prevents collapse.

3. Specialist treatments

Pest control companies use a range of proven methods, including:

• Surface sprays and gels: Applied directly to timber, these penetrate into the wood and kill larvae feeding inside. They also create a barrier to stop new infestations.
   
• Injection treatments: Insecticides can be injected into exit holes, targeting larvae deep within the wood.
   
• Fumigation: In cases of widespread infestation, fumigation may be required. This process fills an enclosed space with gas, penetrating timber and eliminating pests at all life stages.

Each method is selected based on the severity of the problem and the type of timber involved.

4. Reducing moisture and improving ventilation

Borers thrive in damp conditions. Improving airflow under houses, fixing leaks, and keeping timber dry make it less attractive for beetles to lay eggs.

5. Protecting furniture and valuables

Antiques and treasured wooden items require careful treatment. Professional pest controllers may use portable fumigation or other specialised techniques to preserve valuable items without causing damage.

DIY vs professional solutions

DIY sprays and treatments are widely available, but they rarely solve the problem. Most surface sprays do not penetrate deep enough to reach larvae, leaving infestations to continue unnoticed. Common mistakes include treating only visible holes or ignoring underfloor areas where borers are often most active.

Professional pest control offers several advantages:

• Accurate species identification.
• Treatments that reach deep inside timber.
• Long-term protection against reinfestation.
• Safe application by trained experts.

Given the cost of repairing damaged timber, professional treatment is usually the most effective and economical choice.

Preventing future infestations

Prevention plays a major role in protecting timber from borers. Steps you can take include:

• Using treated timber: When building or renovating, opt for wood treated against insect attack.
   
• Sealing timber surfaces: Paint, varnish, or polish creates a protective barrier that discourages beetles from laying eggs.
   
• Ventilation: Ensure good airflow in underfloor and roof spaces to reduce dampness.
   
• Regular inspections: Especially in older homes, annual or biennial inspections can detect infestations early.
   
• Seasonal checks: Summer, when adult beetles emerge, is the best time to look for new exit holes.

By taking preventative action, you reduce the risk of future infestations and extend the lifespan of your timber.

Professional borer control in New Zealand

Rentokil offers specialist borer control services across New Zealand. Our trained technicians carry out detailed inspections, identify the type of borer, and recommend tailored treatments to protect your property. With decades of experience handling local infestations, Rentokil uses proven solutions that reach larvae hidden deep inside timber.

From surface treatments and injections to fumigation for severe cases, our methods are designed to eliminate active infestations and protect against future damage. For homeowners and businesses alike, professional treatment provides reassurance that your property is safe and secure.

Conclusion

Borers are a silent but serious threat to New Zealand homes. Hidden inside timber, larvae can feed for years before exit holes appear — by then, the damage may already be severe.

Getting rid of borers requires more than surface sprays. It demands professional inspection, effective treatments that reach deep into the wood, and preventative measures to reduce the risk of reinfestation. By acting quickly, you can protect the strength and value of your property.

If you suspect borer activity in your timber, don’t wait until the damage is irreversible. Contact Rentokil NZ for an expert inspection and tailored treatment plan to keep your property safe for the future.