Longicorn borers

  • damage caused by two-hole borer
    The two characteristic oval-shaped larval tunnels in heartwood caused by the two-hole borer.
  • damage caused by bulls eye borer on rose gum
    Bulls-eye borer damage to a rose gum stem. The oval groove above the tunnel is characteristic.
  • ringbarking caused by longicorn borer
    Wounds caused by the ringbarking longicorn on a mature spotted gum stem.

General information

Adult longicorn beetles have narrow bodies up to 45 mm long, but are rarely seen. Their presence is more often associated with the damage they cause to tree stems.

Scientific name

Phoracantha solida, P. mastersi and P. acanthocera.

Description
  • adult beetles have narrow bodies, 30-45 mm long. Antennae are as long as or longer than the body
  • larvae are cream, 20-40 mm long with a reddish head and chewing mouthparts
  • initial signs include fine frass (similar to sawdust) around the base of the tree
  • kino bleeding is another early sign of longicorn activity.
Distribution
  • found in south eastern and northern Queensland
Hosts
  • spotted gums (Corymbia species)
  • blackbutt (Eucalyptus pilularis)
  • rose gum (E. grandis) and hybrids
  • Dunn's white gum (E. dunnii)
Damage
  • Initial symptoms may include frass, similar to fine sawdust around the base of the tree, resin exudation (kino bleeding), cracking and, eventually, bark sloughing around the attacked area.
  • Two-hole borer: Early damage is associated with kino bleeds and larvae may create small air holes through the bark. When fully developed, larvae bore into the heartwood to pupate. Falling bark at this stage exposes sapwood and oval-shaped holes packed with frass.
  • Ringbarking longicorn: Large wounds, associated with copious kino bleeding, are caused by larvae feeing under the bark. Larvae feed gregariously, over a large area of the stem. Girdling can kill saplings.
  • Bulls-eye borer: This leaves a characteristic oval-shaped groove around a central hole or 'bulls-eye'. The bulls-eye is usually hidden beneath the bark, when only splits in the bark are visible. When the beetle emerges, the bark falls, revealing the damage.
  • Wounds generally seal as the tree grows.

Further information

Last updated 15 October 2012