Powderpost beetle

An adult powderpost beetle

Adult powderpost beetle.

Powderpost beetle larvae reducing parts of timber to a flour-like powder

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

General information

The powderpost beetle is one of the most important timber borers found in Queensland. The larvae can reduce susceptible timber to a fine, flour-like powder. The beetle can attack seasoned timber causing significant structural damage, often with considerable financial consequences.

For property owners and manufacturers, preventative measures are less costly than treatment.

Scientific name

Lyctus brunneus

Description
  • The adults are up to 7 mm long, dark-brown, shiny, flattened and elongated.
  • Adults have a distinct head and the terminal segments on their antennae appear to be clubbed.
  • The larvae are cream-coloured with brown head and jaws and three pairs of small jointed legs.
  • Larvae, on hatching, are about 0.5 mm long and straight-bodied but later become C-shaped.
Similar species
  • Lyctus discedens (the small powderpost beetle)
  • Lyctus planicollis
  • Lyctus parallelocollis
  • Tristaria grouvellei
  • The Malayan powderpost beetle Minthea rugicollis, which was often found in rainforest hardwoods imported from South-East Asia, is now established in Queensland.
Distribution
  • Powderpost beetle attack in susceptible timber is very common in tropical and subtropical climates in Queensland.
Life cycle
  • Female beetle lays 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 may take from 2-12 months to mature, depnding on temperature, humidity and food supply.
  • Fully-grown larvae tunnel towards the surface and create oval cells within which they pupate.
  • Mature beetles emerge after 2-3 weeks through circular holes (1-2 mm diameter), creating small piles of frass on the timber surface.
  • rRe-infestation is common for up to five years after tree-felling, until the food resource is depleted.
Damage
  • Powderpost (and all lyctine) beetles attack only the sapwood of certain hardwoods and do not attack softwoods.
  • Susceptible timbers must contain enough starch to nourish the developing larvae.
  • The heartwood is never infested, although adults may emerge through it.
  • Most infestations occur in logs or sawn timbers drying at the saw-mill.
  • Infestation may not be noticed until the timber is in-service and adults begin to emerge.
  • Infested timber contains galleries packed with fine, powdery frass.
  • The infested area may be reduced to powder within a shell of wood, perforated by emergence holes.
  • Small piles of smooth, floury frass may be found outside the timber.
  • Infestation may occur anywhere where susceptible timber has been used (for example, in subfloor areas, living space, roof space, or in furniture and artefacts).
  • In new houses, emergence holes may appear in the lining materials (for example, in plasterboard and panelling) and joinery. Such holes are made by adults emerging from the hardwood framing beneath.
Management
  • Damage is best avoided when sapwood from susceptible timber species is removed by the supplier, or by using non-susceptible timber.
  • Where the damage is not significant structurally, control measures may not be needed except where appearances are important.

Further information

To find which timbers have sapwood that is susceptible to powderpost beetle (Lyctus), visit Timber Answers.

Last updated 09 May 2013