There are several types of timber borers in Australia, some serious and some not, so it is important to identify them if you think you have a problem. Borers are actually the larval form of different families of beetles.
While the adult beetles lay their eggs within the timber, it is the larval (grub) stage of borer beetle development that is the most destructive, as the grubs feed on the timber as they grow. Some beetles may spend several years in the larval stage causing significant damage. It is only after the borer have finished their pupal stage and metamorphose into a winged insect that you can see where they have been feeding on by the the flight holes they create when leaving the timber.
Here is a list of common types of borers in Australia:
Pinhole borers: They cannot survive in timber once it has dried out, so they normally leave before, or soon after, the timber is used for construction. You can identify them by the "flight holes" they leave behind. These holes will rarely have borer dust around them, since the insect is long gone or dead. These are relatively harmless because they do not leave as many holes as the more destructive species below.
Longicorns: These leave oval shaped holes 6-10mm in size as they emerge from framing timbers or wall linings. They are not a serious structural problem because they cannot breed in the timber and therefore cannot proliferate. The size and shape of their flight holes makes this borer easy to identify.
Auger beetles: Again these are fairly harmless. Auger beetles leave far fewer flight holes than the more destructive borers since they cannot proliferate in the timbers.
Lyctus Borer (Powder Post Beetle): These borers only attack the sapwood of certain susceptible species of hardwood timber. Sapwood is the living band of wood around the outside of the tree which is commonly used for decorative timbers like skirting boards, small dimensioned battens and timber trims. These timbers could be riddled with lyctids within three to five years of the house being built.
Lyctids can be recognised by their 2mm holes and large quantities of flour-like dust. Although not generally a problem structurally, they are certainly unsightly. If lyctid attack is visible, you could replace the affected timbers. Otherwise they do not need any special treatment.
Anobium Borer (furniture beetle) and Queensland Pine Borer: Anobiid borers are more serious and attack softwoods, especially varieties of pine. Like Lyctids, Anobiids are widespread throughout Australia. The Anobium punctatum species especially loves Baltic pine, occasionally used for floorboards and weatherboards.
Anobiids tend to channel along the grain of the wood, making 2mm pinholes and leaving large quantities of loose gritty dust with a texture of fine table salt. They are capable of eating for years. Be suspicious if your floorboards get spongy as this is a common area for them to attack. You will probably first notice the floor feeling spongy at one end of a large room (like the living room) because a big floor area will deflect more noticeably. Also be aware that second hand or antique furniture and old floorboards may contain borers so examine them well before introducing them into the house.
Anobiid damage must be attended to. Remove all borer-infested timbers and replace them with non-susceptible timbers. Borers thrive in damp conditions so reduce sub-floor humidity by removing debris, cleaning out vents and draining damp soil where necessary.
In some cases Anobiid-infested timbers need chemical treatment. It is recommended that only currently licensed members of your State's pest control association be contracted.
Treating borer affected timber.
Replacement of all susceptible timbers is always preferred should you sell your property in the future as it is likely that an inspector will report the borers as active. A chemical treatment can also be used to control and protect against furniture beetle or Queensland pine beetle. It is a lower cost option but is less effective. Chemical treatments over a number of consecutive years may be required.