Sirex wood wasp
Dr J. King
Sirex wood wasp is an introduced pest of Pinus radiata, P. taeda and some other Pinus species grown in plantations in Australia, P. elliotii is resistant to Sirex. The wasp is also a pest in New Zealand, South Africa and South America,
Photo (above) of the female sirex wood wasp
by courtesy of State Forests of New South Wales.
Female (above): metallic dark blue with orange legs
and a prominent ovipositor (egg-laying apparatus, 'sting').
Length variable, from about 15 to about 35 mm.
Photo of the male sirex wood wasp (above)
by courtesy of State Forests of New South Wales.
Male - head, front half of the body blue-black,
orange abdomen with a dark tip, and no 'sting'.
Length variable, from about 13 to about 32 mm.
Biology
Females are attracted to stressed, sick or suppressed trees. They use the ovipositor to drill holes in the tree, then lay eggs and deposit fungal spores and toxic mucus in the holes. The fungus and mucus act together, the mucus dries the tree tissues, providing the right conditions for the fungus to grow. The tree dies as the fungus spreads. Females also lay in fresh logs, stumps, and trash. The wasp larvae (immature stage) feed on the fungus in the wood. Their tunnels, often along the grain, are filled with pale, granular frass (waste), and may be stained light yellow by the fungus. Fully-grown larvae move close to the surface and cut a chamber where they pupate. Each new adult chews a round emergence hole about 4 mm- 7 mm across, depending on the size of the adult.
Sirex larva: creamy white with an obvious head,
three pairs of very short legs and a cylindrical body
with a characteristic dark spine at the rear end.
The life cycle takes about one year, but can be longer. Adults are present from late November to April, and most numerous in January-February.
Symptoms: externally on the tree or log
Symptoms:
- pale, then copper coloured dry foliage
- fine pin-holes (egg-laying sites) in the bark
- beads and trickles of resin around and below the pinholes
- cambium stained brown
Dead, standing tree with flight holes 4 - 7 mm in diameter
Symptoms: internally in the log and sawn timber
- Tunnels up to about 7 mm across with granular frass, and often stained light yellow
- larvae with characteristic spine present
- pupal chambers close to inner bark.
Infested timber may be prone to decay
The wasp can complete its development in and emerge from seasoned/sawn timber which has not been kiln dried to a core temperature of above 600C.
Further information
- Telephone the DPI&F Business Information Centre on 13 25 23 (Queensland residents; non-Queensland residents phone 07 3404 6999 or e-mail callweb@dpi.qld.gov.au ),
- Contact Dr Judy King, (07) 3896 9716, fax (07) 3896 9447 Email judy.king@dpi.qld.gov.au
This DPI&F Note is also published on the DPI&F's PrimeNotes CD-ROM.
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
Last reviewed March 2005
