Longicorn borers
Bulls-eye borer damage to a rose gum stem - the oval groove above the tunnel is typical
© Queensland Government
Typical oval-shaped larval tunnels in heartwood caused by the two-hole borer
© Queensland Government
Wounds caused by the longicorn ringbarking a mature spotted gum
© Queensland Government
Adult longicorn beetles have narrow bodies up to 45mm long but are rarely seen. Their presence is established by the damage they cause to tree stems.
Scientific name
Phoracantha solida, P. mastersi, P. acanthocera
Other names
- Two-hole borer (P. solida)
- Ringbarking longicorn (P. mastersi)
- Bulls-eye borer (P. acanthocera)
Description
- Adults have narrow bodies, 30–45mm long.
- Antennae are as long as, or longer than, the body.
- Larvae are cream, 20–40mm long with a reddish head and chewing mouthparts.
- Fine frass (similar to sawdust) around the base of the tree is an early sign.
- Kino (blood-red sap) bleeding is also an early sign.
Distribution
- 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
- Early signs (all borers):
- frass (like fine sawdust) around the base of the tree
- blood-red sap seep (kino bleeding)
- cracking and, eventually, bark shedding around the attacked area.
- Two-hole borer:
- larvae may create small air holes through the bark
- adult 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 feeding under the bark
- larvae feed in groups, over a large area of the stem
- feeding that encircles saplings (girdling) can kill them.
- Bulls-eye borer:
- typical oval-shaped groove around a central hole or 'bulls-eye'
- 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.
Resources and research
- Carnegie, A, Lawson, SA, Smith, T, Pegg, GS, Stone, C, and McDonald, J 2008, Healthy hardwoods: a field guide to pests, diseases and nutritional disorders in subtropical hardwoods, Forest and Wood Products Australia, Victoria.
- Pests and diseases image library (PaDIL)
- Last reviewed: 12 Dec 2018
- Last updated: 12 Dec 2018