Pinhole borers attack moist wood, usually as logs in the forest and mill yard, but once the log has been converted to sawn timber their activity ceases, and only the holes in the wood remain to affect its appearance. They do not reinfest, and treatment is not required.
The beetles bore into the sapwood, and often into the heartwood, and the females lay their eggs at the ends of these galleries. The beetles have fungal spores associated with their bodies, which they leave on the inside of the galleries. These spores germinate, and the fungus grows on the moist internal walls of tunnels made by parent beetles.
When hatched, the larvae do not eat wood, but feed on the ambrosial fungus. Larvae are characterised by a fine scroll on the first body segment behind the head. When fully grown, the larvae pupate in the tunnels and emerge as beetles through the holes made by parents.
Often the wood surrounding the holes is stained, affecting its aesthetic appearance, but not its strength. When timber showing obvious pinhole borer holes is used for house construction, the insects are no longer present, and reinfestation cannot occur as the wood is dry. Although the strength of the wood is not significantly affected by the holes, their presence does reduce its acceptability where appearance is important.
- Strongly attracted to freshly felled logs, logging residues and occasionally very moist sawn timber
- Fungal spores are carried into the tunnels by the beetles
- Adults 1-6 mm long, cylindrical and stocky
- Rounded cowl shaped prothorax
- Feed on ambrosial fungus not wood
The spores germinate and the fungal hyphae provide food for the adults and larvae
Xyleborus perforans - Island pinhole borer
Dark staining around holes and galleries - "pencil streak"