What is it?

The Death Watch Beetle (Xestobium rufuvillosum) is an indigenous British insect that infects the heartwood of large hardwood beams, such as oak, ash and horse chestnut.

This insect strongly prefers timber that’s also suffering from fungal decay, such as wet rot, so that the wood fibres have been softened and the nourishment within them has been made readily available to the Death Watch larvae. Death Watch Beetle will infect softwoods if they are well rotted and lie in contact with hardwood.

Because of the combination of fungal decay and infestation, evidence of Death Watch Beetle is a serious ‘ailment’ in a property that can cause significant structural damage and should be rectified urgently. However, because of its rather particular requirements for suitable accommodation, this sort of infestation is rare in normal domestic property and is generally only found in large old buildings such as churches and stately homes.

How to spot it

How to fix it

Death Watch Beetle often causes extensive damage to structural timbers which become hazardous and even prone to collapse. To make matters worse, tunnelling is generally done at the centre of the timber, leaving the exterior looking significantly less damaged than it is. There are therefore four key stages to eliminating this infestation:

• Establish the full extent of the spread and cut out structurally compromised timbers.
  Because a simple visual check to the outside of a timber cannot assess the internal damage, an alternative method must be used. Ultrasound is a very quick and non-invasive technology that accurately reveals the locations of any cavities inside a timber. Where tunnels are revealed, this wood should be cut away, especially if the timber is in anyway structural.
• Woodwork cut away should be replaced with new timbers that have been pre-treated with an effective preservative.
  Pressurisation, double vacuum methods or a 10-minute dip in an organic solvent preservative are effective measures to satisfy the requirements of British Standard BS 5268. Remember to re-treat any cut-ends or joints.
• The conditions that allow damp to develop should be counteracted by fixing any leaks.
  Ventilating properly and warming the affected areas up. Death Watch Beetle is inactive in wood that has a moisture content of less than 14%, so getting the wood to this level and keeping it there should be a priority.
• Keep moisture levels low on an ongoing basis.
  This is somewhat tricky in this country, so to prevent any future outbreaks of Death Watch Beetle, it is highly recommendable to treat any remaining woodwork with a boron-based insecticide and preservative. Several very thorough applications will be necessary.

• Surface sprays tend not to be particularly effective as they do not penetrate into the body of the wood, thereby forcing the larvae and beetles further into the woodwork to do yet more, unseen damage. Therefore, a glycol-based insecticide paste is recommended as this can disperse further through both damp and dry wood to create an effective barrier.

Further information and useful links

• Find a Damp Proofing Specialist near you
• Find a Water Proofing Specialist near you
• Find a Wood Worm Specialist near you
• Find a Masonry Repairs Service near you