Secret Scotland

If it's secret, and in Scotland…

Does Historic Scotland know that woodworm is a con?


A story about furniture (and fabric) preservation caught my eye tonight, as it mentioned woodworm.

The story referred to items within a traditional island home (known as a whitehouse), at Arnol on Lewis:

Staff at Historic Scotland hired a lorry from a local frozen food delivery company and froze the wood and textiles at -30C for four days. Historic Scotland said freezing has been used in the past to kill beetles, their eggs and larvae.

Rona Walker, Historic Scotland’s regional collections manager for the north, said staff had to act quickly to deal with the woodworm. She said: “There are a number of ways in which woodworm can be treated but for historical objects freezing is a popular choice. Freezing at low enough temperature ensures that all life stages of woodworm are eradicated.”

The thing about woodworm is that there is actually no such thing as a “woodworm”, and the term is a generic one, describing the effect of beetles with lay their eggs on, or just below, the surface of wood, usually damp and/or rotting wood, which them provides a handy source of food when the larvae hatch and feel like a meal. They then pupate and emerge as beetle, ready to start the process all over again.

Just to make things even more appetising, the dust seen around the holes they make in wood is not wood or “sawdust” as described by some, but the faeces the larvae excrete as they digest the wood. So, you really don’t want to blow it and get a face, nose, or mouth full of the stuff.

So, where does the con come from?

Some years ago, I came across a book filled with “Trade Secrets” about how to maintain and look after your house yourself, for a fraction of the cost charged by tradesmen, and without being taken for a ride by insurers. (Need I say this book is/was not addressed at any legitimate workers or insurance practices.) Notably, it was written by an ex-insurance underwriter who had seen all the tricks, and reckoned it was time the rest of us knew about them.

He wrote copiously about “woodworm” and the various chemical treatments and cures promoted by preservative companies.

He pointed out that the holes were generally ‘escape holes’ where the beetles had left the scene of their crime, and were no longer present. Provided the wood was dry, and kept dry, then the infestation should no longer continue, nor should it recur. Treatment with chemicals was unnecessary and generally pointless by that stage, as the beetles and larvae were gone and would only return if the wood was damp (and possibly beginning to rot.) Chemical treatments were a waste of money, as there were no creatures to kill, and pointless, since (despite manufacturer’s claims) they do not actually penetrate the wood to the depth of the larvae, or beetle. But it seems that insurance companies like to make people do things like this, and he suggested that they set up companies to sell the treatments, so effectively got the money they made people pay in order to get insurance. And then they got the premiums on top.

So, the bottom line is that once the breeding season is over, and the beetles have left, there is little more to do, other than prevent the beetle’s return to lay more eggs, and that means making sure things are dry.

Freezing is dubious, and from what I have read, needs weeks, not four days if it is to be effective.

But I wonder if it really works, after all, I understand entomologists freeze their bugs to preserve them, as they (the bugs, not the entomologists) and their eggs just go dormant, and unfreeze them later, at which point they come back to life. Some insects revive after cryogenic freezing, while many others survive freezing during the winter.

Better would be irradiation from a nuclear source. Bugs are tough, but it’s a myth that after a nuclear war, the cockroaches would be the only survivors. A big enough dose of radiation kills EVERYTHING. A few thousand rad would do the job nicely, and take only a few hours.

Perhaps less hazardous than irradiation would be the application of sufficient heat to cook the beetles, their larvae, and any eggs. It would help dry the wood (if not done too enthusiastically, avoiding charring or setting on fire) and discourage the return of the offending beetles. Frozen wood will cause condensation and damp, and that’s not so good,

(Ok, it looks like a ladybird, but when you need to use free imagery, you just have to make do with the nearest, and the life cycle is the same for beetles.)

Insect life cycle


June 23, 2013 - Posted by | Civilian | , , , ,


  1. The problem with woodworm is which I think you may have missed in this article is that the larvae can have lifespans of years. The Deathwatch Beetle for instance can exist for over 10 years in a large piece of wood. There are treatments available which you can spray / apply directly into boreholes these days to kill the larvae off which are recommended if you don’t want these creepy insects inside your wood!


    Comment by Jamie | Woodworm Treatment HQ | July 1, 2013

  2. The problem is you may have missed my repeating the revelation by an insider that woodworm treatment is largely a con. He’s not saying it is a con, just that it is usually pointless and of little real effect. Save your money, remove and deal with the cause of the infestation, and you don’t need the nasty costly treatment.

    Trouble is, most chemical treatments don’t penetrate far enough to really be effective, and all you have done is confirm the con of woodworm treatment in general. Once started, you’ll be shelling out for a promise for years, and you dare not stop, or it will be your fault the treatment failed, not the treatment co.

    Surface spraying will only penetrate a few millimetres into heartwood and then only if the surfaces are very thoroughly cleaned down before application. It has been argued that this is sufficient as it will kill the adult as it emerges, but what tends to happen is that the beetles avoid the treated areas and instead emerge, if at all, through joints and other untreated areas. The darkness and relatively stable environment of joints is in any case a favourite habitat of the insect, and any treatment that tends further to concentrate attack in joint areas should be avoided. No new flight holes appear, and the problem is thought to have been solved, but is in fact continuing, unobserved and unchecked. Further, by discouraging their emergence, the beetle’s only natural predator within buildings, the spider, is prevented from exercising any control, if it has not already been killed by the spraying.

    So, treatments could be said to do more harm than good – and we haven’t even touched on the effect of the chemical on people.

    Methyl bromide fumigation works well, but can’t be used in buildings. And more recent water based solutions are even worse at penetrating than their older predecessors.

    Heat treatment has even come in for criticism, as live larvae are still found at the scenes of fires where time/temperature exceeds treatment values to the extent of destroying wood.

    Keeping things dry, and ventilated, or sealing the wood with varnish and paint is best. Stop it before it gets started.

    Don’t take my word for this though.

    Go ask building conservation and preservation experts who give advice for free, but not anyone selling chemicals.


    Comment by Apollo | July 2, 2013

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