Woodworm is much feared by home-owners and landlords alike, and every year millions of pounds is spent on its eradication. But similarly to Dry Rot, there are alternative methods of treating it.
‘Woodworm’ are actually the larvae or grubs of several species of wood-boring insects, of which the common furniture beetle, anobia punctatum is most common in homes. The grubs are only about 6mm long and a little over 1mm wide. I have also come across the deathwatch beetle, xestobium rufovillosum, which has very short, fat grubs about 8mm long and 6mm wide when out of the wood.
There is some misinformation on the internet which claims that woodworm only affects new timber brought into the house already infected from the sawmill. The claim is that after a few years the infection will be gone so no treatment is necessary. This misunderstanding is down to confusion with other species of wood-boring insects that have this habitat.
Common woodworm prefer seasoned wood. Their larval stage is 3 – 4 years, which they spend burrowing through the softer, more nutritious sapwood. They will attack hardwoods and softwoods, but avoid the heartwood of all species. They are particularly fond of old-fashioned plywoods containing highly-nutritious animal-based glues, used in furniture in the earlier part of the 20th century, hence the name ‘furniture beetle’. Exiting adult beetles can mate and re-infect the same wood again.
Furniture beetle shows itself by boring 1 – 1.5mm exit holes in the wood. The exit holes for the rarer Deathwatch beetle are much bigger. Fresh exit holes are indicated by a fine dusting of wood powder. Without the dust, the holes may be very old and no indication of current infestation.
For many years the standard treatment has been spraying affected timbers with insecticides, sometimes with serious health consequences to workers and occupants. Fortunately the more highly toxic chemicals like Lindane and tributyltin oxide aren’t used much now, and less toxic treatments such as Borax have taken over. Still, the question is whether chemical treatment is justified at all. The chemical treatment may not penetrate the wood deeply enough to reach the grubs.
All animals require moisture, and wood-boring insects are no different. I have observed woodworm prefers damp homes and the damper the wood, the more heavy the infestation. Modern homes kept dry should have few problems with woodworm, as the wood effectively becomes a desert incapable of supporting the grubs.
Regarding treatment, in structural timbers, isolate sources of moisture such as damp walls / floors from the wood with a plastic DPM (Damp Proof Membrane). Reduce the humidity by installing efficient central heating and extraction systems for bathrooms and kitchens. If necessary get a dehumidifier. For furniture, move it away from outside walls, reducing condensation on the back. If it’s not precious just get rid of it. Alternatively it may be treatable by drying out completely then leaving in a very dry environment.
If you dry out the wood, you should rid yourself of the pest.