The term woodworm is an inaccurate one, as 'woodworm' is actually a beetle infestation. The damage caused to the timbers is due to the feeding of beetle larvae.
The adult beetle lays its eggs in a crack or crevice within the timber and the larvae hatch soon after. The larvae burrow their way through the timber for many years before emerging as an adult beetle in the warmer Summer months, and when they in turn lay new eggs the infestation process begins again.
It is important to identify which infestation we are dealing with, as some infestations require no chemical treatment whilst others require more particular attention.
The different species of wood boring beetle larvae attack various types of timber. Some larvae live for less than a year while others live up to 11 years before hatching as an adult beetle. The most common infestations in United Kingdom are:
The common furniture beetle is responsible for around 70% of all infestations and attacks softwood and European hardwoods. The emergence hole is around 2 mm in diameter, and active infestation will often be accompanied with cream coloured bore dust. Severe infestation of timber will result in structural failure. Structurally unsound timber should be replaced and then Micra emulsion insecticide preservative applied via spray treatment.
The woodboring weevil will only attack decayed timber that has been attacked by wet rot. The beetle will travel down the grain of the timber forming plough like tracks. The replacement of the decayed timber (isolating it from any further moisture) is sufficient to eradicate this infestation, and no chemical treatment is required.
The deathwatch beetle attacks decayed hardwood and sometimes soft woods that are in contact with hardwood. The name derives from the ticking sound (rather like a watch) made by adult beetles tapping their heads against the walls of the emergence holes to attract a mate. This was often heard in coffins made of oak.
Deathwatch may be a secondary problem, as fungal decay must be present for an infestation to become established. Extreme damage to bearing end timbers can often be concealed in walls that are prone to dampness. It is critical to identify the correct species of decay and insect to eradicate this problem completely.
The house Longhorn beetle (also known as the Camberley Beetle) is the largest of all . An adult is around 12 mm long the larvae are 30 mm long.
The House Longhorn beetle comes from Africa, introduced by accident when returning troops brought it here in their packing cases. It originally established itself in the Camberley area, notably in roof spaces where people stored infested timber.
This beetle does considerable amount of damage to the timber with very little evidence of infestation. The emergence hole is similar to a 4 inch nail hole but underneath the thin veneer of timber are long tunnels filled with sawdust which when joined up cause extensive damage or complete disintegration of the timber.
Treatment : remove structurally unsound timbers and burn on site, then apply solvent based insecticide or paste. Infestations north of London should be reported to the Building Research Establishment, who maintain records of infestation is in the UK.
The powder post beetle attacks European and American hardwoods (principally oak and elm) that have large pores and high starch content not found in softwood.
It is commonly found in properties with newly imported block or stripped flooring or furniture products. Small pin-like holes with small piles of fine cream-coloured dust beside them can be seen.
Once the supply of starch is exhausted, infestation will cease. It is uneconomical and impractical to attempt chemical treatment to floor due to varnishes and mastics that will restrict the treatment being applied to the timber.