Different beetles cause different damage
Woodworm is the everyday name for damage caused by the larvae of several types of beetle. They prefer different sorts of timber, so it is worth finding out which insect was responsible before paying for treatment.
Exit holes are evidence of past emergence
The familiar small holes show where adult beetles left the timber. They do not, by themselves, prove that larvae are still active inside.
Look for fresh evidence
Fresh frass, newly appearing holes, adult beetles and continuing damage are more useful signs of current activity than old dark holes that have been present for years.
Timber condition still matters
Some insect attack is mainly confined to sapwood and may have little structural significance. Other infestations, particularly where timber is already damp or decayed, can be more serious.
Useful technical sources
- Historic England — Timber Treatments and Pest Control
- Historic England — Timber Decay in Buildings and its Treatment
These links provide background guidance. A particular building still needs its own inspection.