Wood borer on damaged timber.
Wood borer infestations: detection and treatment
Discover the five types of wood borers most often found in the timber of houses and furniture in Australia; and information to assist in their detection and treatment.
26 March 2007 | Updated 14 October 2011
Lyctine borers (lyctid or powder post beetles) in the family Bostryciidae are the most common borer attacking seasoned hardwoods throughout Australia.
The main species of concern include:
- Lyctus brunneus
- L. discedens
- Minthea rugicollis.
These are dry timber borers, attacking wood when it has seasoned to moisture contents below 25 per cent.
Lyctines can attack only the sapwood of certain hardwoods, such as:
- some eucalypts
They cannot attack softwoods such as:
A list of lyctine susceptible timbers is provided in Australian Standard 5604.
The female beetle lays her eggs in the pores (vessels) and checks of hardwood timbers, and larvae feed upon starch and other nutrients in the sapwood. Therefore, if the sapwood has insufficient starch, or its pores are too narrow for the female’s ovipositor, the hardwood should be immune to attack.
An iodine test for starch is often used at sawmills to determine the susceptibility of timber. This spot test is described in Australian Standard 1604.1.
As attack by lyctine borers is restricted to sapwood (the trees outer band of living, sap-containing tissue), and as the sapwood band in most eucalypts is thin (25 mm or less), rectangular timber beams sawn from circular logs often lack sapwood, or include it along just one edge or corner.
Therefore, while many houses in the southern regions of Australia (Victoria, South Australia, Tasmania, Perth) have hardwood bearers, joists and scantling timbers, the extent of attack is normally inconsequential, and traditionally, treatment has been considered unnecessary.
The need to treat or immunise sapwood from lyctine beetles is greater in appearance grade products (for example, floor boards and architrave).
Also, the timber cut from plantation and regrowth forests tends to have higher proportions of sapwood, so that the need for immunisation in the southern states is increasing.