Field guide to exotic pests and diseases: Wood wasp
Urocerus gigas (Linnaeus)
Wood wasp adult.
Source: Forest Research, New Zealand
Typical wood wasp circular holes.
Source: Forest Research, New Zealand
Identification: larvae 30mm long, creamy white, with a dark brown spine at the posterior end. Adults to 35mm long, with two pairs of transparent amber wings and a black abdomen with yellow-brown stripes. Females have an ovipositor up to 20mm long. Adults can be confused with other large native Australian wasps and Sirex noctilio.
Hosts: wood of pines and conifers, recently cut, fallen or severely weakened trees, and green timber.
Distribution: Asia, Europe, Chile, USA, Canada and Russia.
Detection:
Larvae: feed on fungus growing on wood within timber, make longitudinal tunnels 15-75cm long (usually tightly packed with frass) from sapwood to heartwood and back. Wood decay (white rot) may be also visible.
Adults: emerge in summer from circular exit holes up to 8mm diameter (this size may vary), pale halos often visible around holes; fly for considerable distances. Females usually lay eggs in weakened trees, often on freshly burned or cut logs. Adults occasionally emerge from timber used in houses or furniture; most likely to enter Australia in pine logs, packing material and unseasoned dunnage.
Potential impact: can kill weakened trees and degrade wood leading to structural damage.