Timber Borers
The two most common timber borers which attack the timber of buildings in Australia are the Anobium Borer (Anobium punctatum) commonly known as the “furniture beetle”, and Lyctus (lyctus bruneus) which is more commonly known as the “powder post beetle”.
THE ANOBIUM BORER
The Anobium Borer mainly attacks the sapwood of softwood species of timber e.g. Radiata and Baltic Pine. This attack usually occurs in those timbers in well established buildings. The adult female beetle lays her eggs in the cracks and crevices of the softwood timber, particularly softwood floor boards and occasionally softwood timber in the roof area. Apart from attacking softwood building components, Anobium Borer is also known for its attack of old hardwood items such as antique furniture, artifacts, icons etc.
The small larvae or grubs emerge from the eggs and initially channel their way along the grain of the timber and later change to move in all directions giving the damaged piece of timber a honeycomb appearance. The larva may feed in the timber for a number of years before changing into a pupa, remaining immobile for 6-8 weeks in this resting stage. The pupa then changes into an adult beetle which bores its way to the surface of the timber where it makes a round exit or flight hole approximately 2.0mm in diameter. The adult beetle then flies within a short distance of the timber from which it has emerged, its sole purpose being to mate with the opposite sex of the same species. The life cycle of the Anobium Borer is usually 2-3 years, however, it can extend to 5-6 years if the conditions are suitable.
The dust or “frass” produced by the borer is often seen in the vicinity of the flight hole, and is coarse and gritty and approximately the same texture as sand. Complete eradication of this borer can only be achieved by fumigation of the timber with registered fumigants, a procedure which, in most cases is impractical in respect of building timbers.
It is recommended that severely damaged timber be replaced with a timber species that is resistant to the Anobium Borer such as Cypress Pine. It is possible to treat the underside of less severely affected timber with a registered product which inhibits the reinfestation of the timber, but does not eradicate those borer larvae already in the timber.
It should be noted that even though there may be Anobium Borer damage to timber it is extremely difficult to define whether activity is present or not.
LYCTUS BORER
The Lyctus or Powder post Borer attacks the sapwood of certain hardwood or pored timbers known as Lyctus susceptible species.
The adult female beetle lays her eggs in the pores situated in the end grain of the sapwood of these particular susceptible species. The eggs change into small curved white grubs which tend to work along the grain of the timber, feeding mainly on the starch present in the timber. When fully fed the larva changes into the pupal or resting stage until, after a short period of time, it further changes into an adult beetle which bores its way out of the timber through small round holes approximately 2.0mm in diameter. The dust or “frass” associated with Lyctus Borer damage in timber is fine and flourlike. Under favourable conditions the Lyctus Borer may complete its life cycle in 4-5 months but normally there is only one emergence per year. It is usual for timber with susceptible sapwood to be attacked within the first year after milling and if the moisture content of the timber is between 8 and 25 percent the infestation will continue until all the starch in the susceptible timber has been consumed.
No treatment is recommended for Lyctus Borer infested timber. Legislation in NSW and QLD limits the amount of susceptible sapwood allowed to be present in framing timber to an amount, which, if it is infested with the Lyctus Borer will not affect the structural viability of the timber and hence the building.
Milled timber is not allowed to contain any Lyctus susceptible sapwood that has not been treated in an approved manner.
