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Attacks the sapwood of all softwood and European hardwood timbers, such as oak and elm
Infests timbers with moisture contents typical of most well ventilated roofs and suspended ground floors but such infestations are usually only of moderate severity and low activity. A severe active infestation indicates a dampness problem.
Dies out in internal joinery, staircases and mid-floors when central heating is installed in existing buildings.
Rarely causes structural weakening except in small-section timbers in particularly damp conditions and in the sapwood edges of floorboards which can be severely tunnelled.
freshly cut exit holes and recently ejected bore dust, although dust may have been shaken from timbers by foot traffic (eg on stairs), and
insect larvae extracted by probing the tunnelled timber. In practice, the larvae are difficult to find.
Identification of the insect causing the damage is important, not only in deciding if any wood preservative treatment is necessary but also in deciding if any other action is needed. Table 1 identifies and classifies insect damage in building timbers into three damage categories so that unnecessary treatment can be avoided.
Infestations commonly cause structural damage, particularly where the timbers affected contain a large proportion of sapwood. In buildings constructed from about 1920 onwards, damage can be significant, but in older buildings where timbers tend to contain lower proportions of sapwood, the significance of damage is usually less.
Assess damage by thorough probing, drilling or sounding as the house longhorn beetle usually leaves a sound skin of wood over the damaged timber.
Attack can be difficult to assess for structural damage as it is often localised in built-in timbers, such as joist ends, or as substantial cavities deep in the centre of large timbers.
Augment surface probing by rigorous probing of timbers where they enter potentially damp walls, by ‘sounding’ with a hammer, and by drilling or probing into large timbers showing evidence of exit holes not associated with sapwood edges.
Damage by Lyctus powderpost beetle normally falls into two categories:
Timbers more than about 20 years old . Any infestation will be extinct. The sapwood edges of large-section hardwood beams in older properties may be damaged, but this is not generally of structural significance.
Timbers less than 20 years old. Hardwood fittings and plywood components may be severely damaged and will usually require replacement.
Weevil infestations of decayed damp timber require no specific remedial measures beyond those necessary to eradicate the fungal decay. Very extensive infestations may cause temporary annoyance to building
The usual treatment is by brush or spray application of a liquid formulation. Pastes are also effective, but their extra cost may be justifiable only where the attack is severe and where timbers are of large dimension or of impermeable species.
The 'treat all timbers' approach is intended to ensure that no further emergence holes will appear elsewhere.
Essential to thoroughly inspect timbers, remove all powdered sapwood and assess the residual strength of damaged timbers.
Expert guidance should be sought on the need for replacement (any replacement timber should be pretreated with an appropriate wood preservative).
Remedial treatment using either organic-solvent liquid or paste is appropriate. Emulsion-based formulations are not recommended because of the potential structural consequences of continued larval activity.
With this insect it is justifiable to completely treat all timbers in, for example, a roof or floor even if only a few members show active damage.
Assess the need for replacement or repair. Special attention is required with timbers set into external walls (such as bearing ends of beams)
Eliminate the causes of dampness and dry out the building, together with application of an insecticide. Drier conditions alone will significantly reduce the scale of an infestation. Insecticides are normally used to speed the eradication process.
Spraying has to be supplemented by injection into emergence holes and holes drilled into large-dimension timbers. Pastes are suitable for localised damage.
Where there is no structural weakness insecticidal smokes can reduce the infestation. A minimum of 10 annual treatments will be required.
In modern properties the presence of paint or varnish finishes on infested items usually makes insecticidal treatments impractical and replacement of the timber is generally the more cost-effective option.
Hardwood block or strip flooring can present particular problems in treatment, especially when laid into bitumen adhesive. Such floors are normally laid with susceptible sapwood faces to the underside, making effective insecticidal treatment almost impossible. Even if any surface finish is first removed. upper heartwood faces are usually impermeable. There is also a risk of staining as a result of leaching of the bitumen by any solvent in the treatment fluid.
In-situ fumigation under a polyethylene sheet may be the only effective method of treating such floors.