How to deal with woodworm

How to deal with woodworm

A peppering of tiny woodworm holes adds rather a distinguished note of character to old timbers, but doesn’t necessarily mean you have uninvited guests because the infestation could be long since dormant. In this article we look at what the term ‘woodworm’ encompasses, how to go about identifying the species, the damage woodworm can cause and the various treatments available.

Woodworm can be found in any part of your home where there is timber, if the right conditions exist for the infestation. Different species of woodworm have preferences for varying types of timber and situations, for instance: roof joists, skirting boards, floorboards or joists and furniture. Typically, though not exclusively, the woodworm also prefers damp conditions.

  • Not all woodworm needs specialist treatment so seek advice from more than one source
  • Ensure any timber contractors are PCA members
  • Always seek a guarantee for any work carried out
  • Woodworm holes can be filled with beeswax and turpentine (or left to add character!)

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What is woodworm?

Woodworm isn’t confined to one particular species; it actually refers to the larvae of any wood-boring beetle. The most common form is the Common Furniture Beetle (Anobium punctatum) but Deathwatch Beetle (Xestobium rufuvillosum) and House Longhorn Beetle (Hylotrupes bajulus) may also be present.

Typically beetles prefer damp conditions, specifically timber with a moisture content of 18% or more. Having found a nice damp spot, beetles lay their eggs and it’s their larvae that do the damage, burrowing beneath the surface of the wood eating their way up and down the timbers until pupating and hatching out, boring their way into the open air through “flight holes”. So the presence of holes actually indicates that there has been an infestation, not that there is still an infestation.

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What are the symptoms of woodworm?

To determine whether your woodworm are still active look out for the following activity around the holes in your woodwork:

  • fine powdery bore dust coming out of holes
  • adult beetles emerging from the holes (particularly during the April-September period when they emerge from the wood to breed) or present in your house
  • presence of larvae when the surface of the wood is scratched away.

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How do I identify my species of woodworm?

Not all woodworm are harmful so the first step is identifying your species before deciding on treatment. Either visit the British Pest Control Association (BPCA) or take a trip to the library and read the book Recognising Wood Rot and Insect Damage in Buildings by Bravery et al. Below are some pointers on determining your type of guest:

  • The Common Furniture Beetle typically attacks softwood species leaving tiny holes measuring 1-2mm. Damp floorboards, loft timbers and old furniture are favourite destinations, particularly where the finish or polish has worn off.
  • The House Longhorn Beetle is rare in the UK but seems to like Surrey as various cases have been spotted there. The beetle favours roof timbers where it attacks the sapwood of exclusively softwood species, leaving holes that are significantly larger than the Common Furniture Beetle and causing severe structural weakness.
  • The Deathwatch Beetle loves wet, decaying hardwoods like oak, ash and chestnut, particularly those throughout southern England. The damage this beetle causes can be more extensive than first thought because the larvae tunnel towards the centre of the timber; also because it has a 10 year lifecycle.

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How is woodworm treated?

  • The Common Furniture Beetle rarely causes structural weakening so DIY treatment is recommended. Two coats of water-based, vapourless and odourless ‘boron’, either brushed or sprayed on, should do the trick.
  • The House Longhorn Beetle is a notifiable pest and requires professional treatment by a Property Care Association ( PCA).
  • The Deathwatch Beetle burrows deep so it can cause extensive damage and requires more than surface treatment. Advice from a professional surveyor is recommended before proceeding with treatment which typically involves injecting the wood with boron.

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How much does it cost to treat woodworm?

A blanket pesticide treatment for an average house costs between £500-£1,000 and Boron surface treatment for light to medium infestation costs around £28 per 25 square metres. Injectable gels and pastes are more expensive, so too are leave-in rods that remain in timber suffering dampness. Permethrin is a cheaper alternative to Boron but is toxic to fish and other pets so exercise caution.

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How do I prevent woodworm returning?

  • Keep humidity levels low and ensure good ventilation. A good investment is a timber moisture meter with a probe that inserts into the wood to determine moisture levels. A reading below 12% means a low risk of infestation.
  • Remove and replace affected wood to avoid woodworm spreading.
  • Install ultraviolet insect killers to kill emerging adult beetles between April-September.

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