Woodworms: detection, prevention & treatment

Need to get rid of woodworms? Here is everything you need to know about detecting and treating woodworms at home or in the garden.

The woodworm can be a destructive pest. Actually beetle larvae, woodworms feel particularly at home in damp wood, where they survive for many years, surrounded by their favourite food. Here, we describe measures you can take to prevent woodworms entering your home, and outline methods for dealing with an infestation.

Note: If you are fighting woodworm, be sure that the wood can tolerate it. High quality furniture or wooden instruments are easily damaged. Always consult a professional if you are unsure.

Woodworm: profile and characteristics

Woodworms are the larvae of the common furniture beetle (Anobium punctatum). An adult beetle is 2.5 to 5 millimetres long and slightly hairy, with a neck shield that protects its head. The beetles can fly and will spread quickly, so be warned. However, they tend to prefer their larval wood most. It is the larvae that eat wood; adult beetles merely look for a partner and reproduce. The grubs hatch from 0.5mm long eggs and quickly burrow into their wooden home. There will develop through several stages. Depending on the conditions, development can take anywhere from one year to eight years.

Contrary to what you might think, woodworms do not consume any old wood. In fact, they are connoisseurs of hardwood, preferring the wood’s softest areas. This is why trees are spared their inner wood, which is harder than the outer layers. In fact, woodworms differentiate between springwood and summerwood. Springwood grows faster and is therefore softer for the woodworms to chew on.

Recognising a woodworm infestation

Woodworms avoid fresh wood. Apart from that, all wooden furniture, utensils, window frames, roof trusses and ornaments are fair game. And you shouldn’t have any difficulty spotting an infestation. If you suspect woodworms are afoot, check for small holes. Woodworm holes are usually 1 to 2mm in diameter and sporadic. In some cases, woodworms might even have penetrated your objects entirely. Unfortunately, these holes won’t help you determine if the larvae are still present or have moved.

To find out if woodworms are still occupying your possessions, look for sawdust. If you find some, put a sheet of paper (the darker the better) directly under the hole. If any new sawdust lands on the paper, this is a sure sign that woodworms are still at work. This may take a few days, so be patient. Some have said that you can hear the chewing sounds of woodworms if it is quiet enough. However, we never have!

If you do have an infestation, it is time to get to work; whole chair legs can go missing if woodworms are left to their own devices.

Preventing woodworms

Of course, the best way to minimise woodworm damage is to prevent woodworms from ever entering your wood in the first place. Some preventative measures are easy to implement – others can be costly. One easy solution is to keep your wood warm and dry. Heated rooms are best, as the moisture levels are normally very low. Woodworms only survive in wood if it has a residual moisture content over 10%. Cellars, attics, churches, empty buildings and sheds are all susceptible to an infestation.

For wood left outside:

• never lie it directly on the ground.
• protect it from moisture with a waterproof varnish.
• apply preventative, organic insecticide.

A simple glaze that protects the wooden surface should do the trick. Expensive, poisonous chemicals should only be used in extreme circumstances; they tend to damage the environment.

Treating woodworms

In principle, treating a woodworm infestation is fairly simple. So simple in fact, that countless remedies are available online. Some suggest using vinegar; others espouse ammonia solution or petroleum. Though these products may well solve your infestation problem, they will also leave your wood stained and odorous. Here, we present two environmentally-friendly methods to treat an infestation: effective on woodworms and gentle on wood.

Treating woodworm with heat

This method is used by the professionals. It relies on the fact that woodworms die at 55°C, but wood and lacquer tend to be fine. Simply place your wood in an oven for three hours and you will be woodworm free! Larger pieces can go in a sauna if you have one. For most people, however, direct sunlight is a fine alternative. During summer, cover your larger pieces in airtight, black foil, and let them roast. Be sure to use a thermometer, as temperatures can quickly rise above 50°C under foil. Again, three hours should be enough, unless you are dealing with particularly thick wood (more than 6cm), in which case they may need a little longer. And if the sun doesn’t suffice, try placing your wood in a car or greenhouse under the sun.

Important: Cool down the wood slowly (preferably overnight) underneath the foil. If you immediately remove the foil, the wood may crack. The same applies if you are using an oven or sauna.

Treating woodworms with alcohol

For this method, use pure, isopropanol alcohol. It is cheap and will evaporate without leaving any residue. For larger objects, the alcohol might evaporate too quickly, so only use alcohol with your smaller pieces. In fact, if too much alcohol evaporates, you will be left with a highly explosive isopropanol-air mixture. So be sure you are in a well-ventilated room or outside. Your wood will withstand this method well, but certain lacquers and surface treatments can be damaged. If you are unsure whether your wood is treated or not, try applying a small amount of alcohol to an inconspicuous area of the wood.

To apply the alcohol, brush it all over the wood. Apply as much as possible as quickly as possible, especially over any holes. Wrap the wood tight in plastic film and allow the isopropanol to sink into the wood for three days. If your wood is not too thick (less than 3cm), the alcohol should have made short work of the woodworms, and you can remove the film.

Using damaged wood

Woodworm damage is not only ugly; it can be dangerous. With large enough infestations, wood damage can harm the object’s physical integrity. A leaking roof or compromised foundations may be the result of woodworms. In this case, seek professional advice. DIY methods are ineffectual for thick, roof beams and pest control services will be able to provide comprehensive advice. They may suggest using gas treatments, which are only available with the right equipment.

Woodworms look very similar to chafer grub larvae. Know how to tell the difference? Have a read of our article to find out.