How Termites Attack Wood: A Scientific Approach
The Wood Guide · Reference
ReferenceTermites and wood
Termites don't eat wood because they like the taste. They eat cellulose, and they can only do that thanks to micro-organisms in their gut.
- Cellulose is the target
- Rare in Belgium
- Some species are avoided
Termites don’t eat wood, they eat cellulose
Wood is largely cellulose: long chains of sugar molecules. For almost every animal it is indigestible. For a termite it is food.
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Use the arrows or the bars to move through · Isoptera, the termites.
What termites actually do
A termite cannot digest cellulose on its own. The micro-organisms in its gut do that work.
Wood consists largely of cellulose, and cellulose is indigestible for almost every animal. Termites have protozoa and bacteria in their gut that break the cellulose down into sugars the insect can absorb. Without that symbiosis, a termite in a wooden beam would simply starve.
That immediately explains why some wood species are left alone. Tropical hardwoods contain extractives — resins, oils and phenols — that are toxic or repellent to that gut flora. The wood is no harder to bite; it has been made indigestible.
In Belgium and the Netherlands, termites are not an everyday concern. They rarely occur here, and the classic wood-destroying organisms in our region are woodworm, longhorn beetles and above all fungi. Building in southern Europe or the tropics is a very different story.
Small round exit holes of one to two millimetres with fine bore dust below point to woodworm, not termites. It is the most common insect attack here, and the approach is quite different.
- What they eat
- cellulose, digested by gut flora
- Why some species are avoided
- extractives disrupt that gut flora
- In Belgium and the Netherlands
- rare
- Common here
- woodworm, longhorn beetle, rot fungi
- Recognising termites
- tunnels in the wood, soil-tube-like passages
- Recognising woodworm
- round holes of 1–2 mm with bore dust
- Best protection
- keep it dry and off the ground
To be fair: no wood species is fully termite-proof. Even species known to be resistant are attacked when they stay damp for long periods or when sapwood has been included — sapwood does not contain the protective extractives. If you rely on natural resistance, you also need to look at the actual wood you buy, not just the species name.
How the infestation progresses
- Looking for moistureTermites need moisture. They look for wood that is in contact with the ground or that stays permanently damp because of a leak.
- Gaining accessSome species build tunnels of soil and saliva up a wall to bridge dry ground. Such tubes are the clearest sign.
- Eating from withinThey work along the soft earlywood rings and leave the outer layer intact. That is why an infested beam often still looks normal from the outside.
- SpreadingAs long as there is moisture and cellulose, the colony carries on. Damage is usually only discovered when the wood sags or sounds hollow.
Tap along a suspect beam with a screwdriver. If it sounds hollow in one place while the rest sounds solid, something is wrong — whether termites, woodworm or rot. Then probe: if the screwdriver goes straight into the wood, there is loss of cross-section.
Which wood species resist
| Species | Resistance | Why |
|---|---|---|
| Teak | high | high content of oils and extractives |
| Azobé | high | extremely dense and rich in extractives |
| Iroko | high | naturally durable heartwood |
| Robinia | good | the European class 1 species |
| Oak (heartwood) | moderate to good | tannic acid acts as a deterrent |
| Spruce and pine | low | few extractives; treatment needed |
| Sapwood of any species | low | does not contain the protective substances |
Where termites are a real risk, wood choice is combined with structural measures: wood that never touches the ground, metal barriers between foundation and woodwork, and pressure-treated wood in the most exposed zones. None of these measures works on its own — it is the combination that counts.
What you can do yourself
Keep wood dry
Moisture is the common condition for termites, woodworm and fungi alike. Repairing leaks and providing ventilation solves more than any product.
Wood off the ground
Posts on post bases, cladding with a cavity, and nothing lying directly on soil.
Don't stack wood against the wall
Firewood or building material against the wall is an invitation — for insects and for moisture.
Choose heartwood
Ask for wood without sapwood for uses where attack is a risk. Sapwood is vulnerable in every species.
Check every year
Look at crawl spaces, beam ends in walls and the underside of wooden structures. That is where it starts, and where nobody looks.
If in doubt: have it inspected
Insect attack in a load-bearing structure is not a DIY diagnosis. Have it assessed before you remove anything.
Frequently asked questions about termites and wood
Do termites occur in Belgium?
Rarely. In our region, woodworm, longhorn beetles and rot fungi are the common wood-destroying organisms. Termites are mainly a concern in southern Europe and the tropics.
Why do termites eat wood?
For the cellulose. They cannot digest it themselves; micro-organisms in their gut break it down into sugars the insect can absorb.
Which wood species do they leave alone?
Species with a lot of extractives: teak, azobé, iroko and robinia. These substances disrupt the gut flora the termite depends on.
Is there wood that is fully termite-proof?
No. Even resistant species are attacked when damp for long periods, and the sapwood of every species remains vulnerable.
How do I tell woodworm from termites?
Woodworm leaves round exit holes of one to two millimetres with fine bore dust below. Termites leave tunnels and sometimes soil tubes against walls.
What is the best protection?
Keep it dry and off the ground. Moisture is the common condition for virtually all wood attack.
More in The Wood Guide
Durability classes, woodworm and which species hold up outdoors.
Have a question about your project? Just ask — we're happy to help.
Photos via Wikimedia Commons: Isoptera — Marco Vinci, CC BY-SA 3.0 · Block of wood eaten away by termites into a network of tunnels — Pratishkhedekar, CC BY-SA 4.0 · Reticulitermes banyulensis — Hans Hillewaert, CC BY-SA 3.0