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Woodworm is a generic term used for the larvae of woodboring beetles that burrow into wood, causing damage to its structure over time, though the term is commonly used to describe the common furniture beetle (Anobium punctatum). The larvae enjoy nothing more than chewing their way through items such as floorboards, staircases, roof timbers and joists, but can equally infest smaller wooden items such as tools and furniture. They can cause the wood they infest to become riddled with holes, weakening its structural integrity and weight-bearing properties.
Agricultural buildings that come to the market for development have often been exposed to the elements, and this can contribute to factors that increase the risk of woodworm infestation such as high levels of moisture and fungal decay.
The damper wood becomes, the easier it is for larvae to bore through and live in it. Woodworm is less of an issue in wood with a moisture content of less than 8 to 12%, making wooden items and structures with a typical moisture content of around 15% a perfect breeding ground for woodboring beetles.
In most agricultural buildings where softwoods such as pine are present, common furniture beetle is normally the issue. However, where developers often hit issues after development is with timber frame buildings constructed of oak where there is or has been fungal decay. Water often runs down structural timbers into joints, providing perfect conditions for fungal decay and deathwatch beetle (Xestobium rufovillosum) infestation. If this risk is not taken seriously and the timbers are not dried and treated as required, beetle emergence can occur many years after the property is completed. By that time, the infested timbers will often be buried behind studwork, making the problem difficult to address. What is even worse for occupants can be the large numbers of beetles emerging in the spring and the knocking from within the timbers as adult beetles communicate with each other. It should be noted that replacement green oak timbers can already have infestations of deathwatch beetle and powderpost beetle (Lyctus sp) brought in from the forest, and these can continue to develop in situ.
There are five easy ways to spot an active infestation before it causes problems with your agricultural building conversion:
• Tunnels and fresh exit holes in wood:
Woodboring beetles leave wood upon maturity by tunnelling out of the timber, leaving small ‘flight holes’ in the surface. During ‘woodworm season’, it is not uncommon to notice these small, round holes (around 2mm) appearing in wood as adult beetles emerge – after which they can live for days or even months. These holes will look fresh, without paint or dust in the hole.
• Bore dust (frass):
Look out for small piles of frass around wooden surfaces, especially near flight holes. It is often spotted below the infested timber and, if found, it indicates that the woodboring beetle infestation is still active.
• Weak and crumbling wood:
If there are many tunnels and exit holes then it can cause wood to crumble, particularly around the edges of floorboards and roof joists. In the case of crumbling wood, the damaged section may need to be replaced.
• Live adult beetles:
Depending on the species, adult woodboring beetles typically emerge between April and September, so if spotted, they are a clear sign of an active infestation. Unfortunately, once they leave the timber, they will be looking to mate and start the whole process again.
• Larvae:
Woodworm larvae are rarely seen as they remain within the wood, but are small, fly, maggot-like larvae, curved in shape and usually a creamy white colour.
If you are unsure how to identify or treat a woodworm infestation, it is best to seek professional help. A certificated surveyor can ensure that your agricultural building conversion has a tailor-made treatment plan guaranteeing any woodworm infested areas are targeted and treated.
Typically, it is only possible to tell if there is an active infestation when damage to the wood has already occurred, so be sure to take immediate action. DIY products can help treat localised infestations and are suitable for smaller items, such as furniture.
For bigger and structural items, property care professionals have a range of treatments available. Early identification and gaining a full understanding of the extent of your woodworm issue is key to preventing it from developing into a more serious problem.
Although not the subject of this article, it is worth noting the problems caused by water-soluble salts, particularly nitrates from farm animal waste, that are common to agricultural buildings. As the building dries, these salts can disfigure surfaces and, being hygroscopic, will pull moisture into the masonry. There are ways of dealing with them during the development, such as lining the structure with a plastic membrane if this is acceptable. But if this is missed or left too late, it can become an expensive issue to remediate.
