Powderpost beetle

Adult powderpost beetle

Larvae of powderpost beetles can reduce susceptible timber to a fine flour-like powder

The powderpost beetle is one of the most significant timber borers found in Queensland. The larvae can reduce susceptible timber to a fine, flour-like powder.

The beetle attacks seasoned timber, causing significant structural damage and considerable financial loss. For property owners and manufacturers, prevention is less costly than treatment.

Scientific name

Lyctus brunneus

Similar species

Lyctus discedens (the small powderpost beetle)
L. planicollis
L. parallelocollis
Tristaria grouvellei
Minthea rugicollis (Malayan powderpost beetle, now established in Queensland due to presence in imported rainforest hardwoods from South-East Asia

Description

Adults are flat, up to 7mm long, dark-brown, and shiny.
Adults have a distinct head and the terminal segments on antennae appear clubbed.
Larvae are cream-coloured with brown head and jaws and 3 pairs of small jointed legs.
Larvae, on hatching, are about 0.5mm long with a straight body that later becomes C-shaped.

Distribution

Widespread in Queensland's tropical and subtropical climates.

Damage

Attacks only the sapwood of susceptible hardwoods and not softwoods.
Occurs in timbers that contain enough starch to nourish the developing larvae.
Heartwood is never infested, although adults may emerge through it.
Occurs in logs or sawn timbers drying at the sawmill.
May not be noticed until the timber is in-service and adults emerge.
Contains galleries packed with fine flour-like powder.
Infested areas may be reduced to powder within a shell of wood, perforated by exit holes.
Small piles of smooth, flour-like powder may be found outside the timber.
May occur anywhere that susceptible timber has been used (e.g. in subfloor areas, living space, roof space, or in furniture and artefacts).
Re-infestation is common for up to 5 years after tree-felling, until the food resource is depleted.
In new houses, exit holes may appear in the lining materials (e.g. in plasterboard and panelling) and joinery. These holes are made by adults emerging from the hardwood framing underneath

Biology

Female beetles lay up to 70 eggs in sapwood containing starch, which is essential for larval growth.
Eggs hatch after 14 days and the larvae create tunnels along the wood grain as they feed.
Larvae take from 2–12 months to mature, depending on temperature, humidity and food supply.
Full-grown larvae tunnel towards the surface and create oval cells within which they pupate.
Mature beetles emerge after 2–3 weeks through circular holes (1–2mm diameter), creating small piles of fine flour-like powder on the timber surface.

Monitoring and action

Avoid damage by having the supplier remove sapwood from susceptible timber species or by using non-susceptible timber.
Where damage is not structural, treatment may not be needed except to repair the timber's appearance.

Last reviewed: 12 Dec 2018
Last updated: 12 Dec 2018

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