The Handyman's Pocket Book: Furniture Beetle.

In the springtime it is a common occurrence for a man to discover a number of small holes in his furniture.  Generally it is accompanied by a little pile of dust, and the realisation comes that the furniture beetle or wood worm is at work.  It calls for immediate action, and here we describe the pests which may be at work and suggest remedies.  We are indebted to the Forest Products Research Laboratory for much of the information given.

Take two typical cases.  A man bought some oak utility furniture a year or so ago, and in the early summer noticed a number of small holes in the side framing of a sideboard.  He pulled it out from the wall to get a better look at the damage, and then found that the back was even more badly affected than the rest of the wood.  On the horizontal surfaces were little piles of fine dust around the holes, and it was then remembered that the floor had recently had a dusty appearance beneath the sideboard.

In the second case an early Victorian oak cupboard had been bought, and holes were again noticed during late spring or early summer, also with little piles of dust.  The back was of softwood and also showed a few holes, though it was not so badly attacked as the main oak structure.

Without actual identification all the indications are that these represent two distinct and separate kinds of pests.  Both have this in common, that they have the same grub - pupa (chrysalis) - beetle history, but they have no connection with each other.  In the first case the powder post or Lyctus beetle is probably at work; in the second it is the furniture beetle, and one is able to deduce this from knowledge of the habits of the two pests.

POWDER POST BEETLE (Lyctus).  This beetle attacks hardwoods, and it is always the sapwood for which it goes.  Comparatively recently seasoned wood is its preference - in fact if can generally be taken that wood which has been seasoned for more than ten years is immune.  Softwoods are entirely free from it.  It follows then that when wood worm is discovered in a newly made piece the probability is that it is the Lyctus beetle at work, especially as the furniture beetle prefers old wood to new.

A point to realize is that the timber may have been infected before being built into furniture.  Suppose you make, say, a table from some oak boards you have bought at a timber yard.  There might easily be no visible signs of infection in the boards themselves, but a year later you might find the tell-tale holes in the sapwood with their little mounds of dust.  Indeed, the menace in the timber yard is realized today, and some merchants make a practice of spraying their stacks with a solution of D.D.T., a process which has proved very effective.

The pest operates in this way.  The beetles deposit their eggs in the pores of the sapwood of hardwoods - they have an uncanny capacity for finding the sapwood.  The eggs hatch out within a fortnight and the grubs begin to tunnel into the wood.  They are so minute that it is impossible to detect either them or their borings with the naked eye.  As they eat their way into the wood they grow, and the tunnels they make grow larger in size.  For a year at least, the grub eats its way along in the thickness of the wood entirely out of sight and leaving no trace until ti eventually bores to within a short distance of the surface when it passes to the pupal or chrysalis stage, and then emerges as a beetle which bores its way out and flies off to begin the cycle of events all over again.  How it knows which way to go to reach the surface is a mystery.

If follows from this that when you discover newly made holes in the wood it is the flight holes you are finding, not places where the wood has been attacked and that the timber has been infected for at least a year.  It is then quite possible for you to buy infected wood at a yard, neither you nor the merchant realizing it, only to find that your furniture is worm eaten a year or so later.  One moral is never to use sap-wood - it is bad practice anyway.

FURNITURE BEETLE.  The life cycle of this pest is similar to that of the Lyctus but it takes about two years or longer in the process.  It is clear then that discovery of holes means that the wood has been infected for at least two years.  It preferences, however, are rather different.  It goes for softwoods as well as hardwoods, and attacks the heart in addition to sapwood, though some woods appear to be immune - mahogany for example.  Newly felled and seasoned woods too are seldom touched, older woods being chiefly attacked.

The beetle can fly so that infection can take place from one item to another even when they are not in actual contact, and also through an open window.  Sometimes they are seen crawling about on a windowsill during summer and people wonder what they are.  They measure from one-tenth to one-fifth of an inch in length and are of a reddish to blackish-brown colour.

REMEDY.  The two chief ways of destroying either the powder post or the furniture beetle is by direct contact with an insecticide or by fumigation with a poison gas.  The latter is a dangerous process which requires expert handling and is suitable only in certain cases.  Since the grubs breathe, they are destroyed by the fumes which penetrate into the holes providing that they are reasonably clear.  Items which can be placed bodily in an airtight chamber can be treated, and it is sometimes possible to fumigate a room by plugging up all holes.  It should be realized, however, that whilst the process may destroy existing life in the wood it does not prevent further attack, so that the application of a liquid insecticide is desirable after fumigation.  The work can only be carried out with safety by firms specializing in it.

For general use a liquid insecticide is more suitable.  There is no substance which is likely to be completely effective in a single application, but there are proprietary liquids which are successful over a period if persevered with.  The grubs eating the substances are killed, but the difficulty is that of reaching them.  One theory is that, since the beetle has eventually to cut its way through to the surface, it is bound to be killed if the entire surface is coated with the insecticide.  This, however, must be accepted with some reservation, because, whilst the grub eats and digests the wood as it bores its way, the beetle does not eat the wood; it merely bites its way out; and it is in the beetle state that the pest emerges from the wood.

As far as possible the liquid should be squirted into the holes.  The old type of fountain pen filler can be used, and some firms provide a special injector the nozzle of which can be inserted in the holes.  In any case, however, the entire surface should be wiped over with the liquid so that in the event of eggs being deposited the emerging grubs are bound to eat it if they are to reach into the wood.  Many of these proprietary insecticides are claimed to have no injurious effect on a polished surface.

It should be realized that it is unlikely that one application will be effective.  When the trouble is first realized the pest will have been at work for at least a year and, in the case of furniture beetle, for two years.  Furthermore, since the holes are made by the beetle in its flight from the wood, merely to put the liquid into the holes is rather like bolting the stable door too late.  The insect has already gone.  However, the tunnels frequently lead one into the other and grubs left in the wood may be reached in this way.  Furthermore, the beetle selects odd corners, cracks, and old flight holes in which to lay eggs, and the presence of the insecticide should sterilise eggs.  It is important, however, that the entire surface should be treated, particularly during late spring and early summer, and that the application should be repeated at intervals during that period for a couple of years.  A wise precaution is also to treat other woodwork items standing near.

Sterilization of furniture by heat is effective when practicable, but it is generally impossible, since the  wood itself is liable to deteriorate under the heat, and any glue of the animal type would be liable to soften.