Wood boring insect flight holes in roof rafter

Damage caused by that commonly referred to as woodworm is actually caused by a beetle larvae. These larvae hatch from eggs laid on the outer surface of timber, where once hatched they burrow into the wood, creating tunnels as they feast.

It can take up to five years for the grubs to reach maturity. Before which they form a pupae eventually emerging as beetles and leaving characteristic flight holes in the timber surface.

Timber damage from wood boring beetle should not always be cause for alarm. For instance some larvae can only feed on damp timber. Once the cause of damp has been rectified the food source, and thus the larvae, will be stopped. In some cases the pest may have been present in the timber prior to construction and the process of sawing, drying and treatment will have killed any larvae leaving only residual damage as evidence of their existence.

The type of timber, size of flight holes, type of dust, or “frass”, left behind and condition of affected timber are all indicators of the type of species and likely damage that can be expected.

In cases where beetle larvae are active they have the ability to cause structural damage and remedial insecticidal treatment is often required.
Damage can be caused to sapwood (the outer rings where sap rises in a tree) and heartwood (the inner rings or ‘heart’). Darker heartwood damage is less common due to the presence of chemicals acting as a natural repellent. Heartwood damage is considered serious as the structural integrity of timber is greatly reduced when heartwood is attacked.

The death watch beetle is considered a particular menace as it feeds off both heartwood and sapwood.

The beetle most commonly referred to as woodworm is the Common Furniture Beetle (Anobium Punctatum). This beetle’s larvae are found to be present in sapwoods of both softwoods and European hardwoods. Infestations are common throughout the UK. Attack is rare in dry wood and modern timber panels such as plywood. It is most common when timber is damp. Where timber is exposed to good central heating this type of larvae usually dies out. Unheated and humid areas of properties such poorly ventilated roof and sub floor voids are most at risk. The larvae live for 2-5 years. Tunnels are numerous and close knit. Bore holes are circular and up to 2mm in diameter. Beetles emerge in late Spring and Summer.

Although treatment can be undertaken through drying out of timber, insecticidal treatment of live infestation is often recommended in order to swiftly arrest the damage.