Active vs Historic Woodworm: How to Tell the Difference
Old woodworm holes are common and often harmless. Learn how to tell active from historic woodworm with simple dust, hole and beetle checks before you pay.
Most older homes have woodworm holes somewhere. Many of those holes come from beetles that died out long ago. Treating dead damage wastes money, so the first job is to find out whether the beetle is still active.
This guide shows simple checks you can do at home. It also explains what a surveyor does when the answer is not clear.
Why it matters
An active infestation keeps eating the wood. Each new generation lays more eggs, so the damage grows. A historic one has stopped, often because the timber dried out.
The two need different responses. Active beetle needs treatment, while old damage needs only a check on whether the wood is still strong.
Signs of an active infestation
Look for these clues:
- Fresh, pale dust that returns after cleaning
- Clean holes with sharp, light edges
- Live or freshly dead beetles in late spring and summer
- Damp timber, or timber that was recently damp
Fresh dust is the clearest clue. It appears only when larvae are working inside the wood.
Signs of a historic infestation
These clues point to old damage:
- Dull, dark holes, sometimes with paint or polish over them
- Grey, caked dust that does not return
- No beetles and no new holes
- Dry, stable timber
A simple test
Follow this test for a few weeks in summer:
- Vacuum all the dust from around the holes.
- Mark a few holes with a pencil, or fill them with a little filler.
- Cover the dusty spot with a sheet of dark paper.
- Check again after two to four weeks.
New dust on the paper, or fresh holes, prove the beetle is active. If nothing changes, the damage is probably old. Because beetles emerge mainly in warm months, the test works best from late spring to late summer.
When the answer is unclear
Some cases are hard to judge. A surveyor can probe the wood, measure moisture and look for live larvae. They may also advise you to monitor the timber for a season before you spend money.
Read our guide to the signs of woodworm for a full checklist. If you need a firm answer, a woodworm survey will give one.
Why damp matters
Beetle prefers damp wood. If the timber has dried out, the colony may fade by itself. For that reason, fixing leaks and clearing air bricks can end an infestation, or at least stop it spreading. The post on how quickly woodworm spreads explains more.
If it is active
Name the beetle, check how far the damage goes and choose a method. Our guide on how to treat woodworm walks through the steps. You can also request a survey to compare written quotes.
Local housing changes the risk. Read about woodworm treatment in London and woodworm treatment in Manchester to see what affects homes in each area.
To go deeper, read about the common furniture beetle and the spray treatment, because the right method depends on the beetle.