Pest profile

Sirex Woodwasp

Sirex noctilio · Hymenoptera: Siricidae[3]

The sirex woodwasp is an invasive horntail from Europe, Asia and North Africa that lays eggs in stressed pines along with a fungus and venom that can kill the tree; it was first found established in North America in 2004.[1][2]

Female sirex woodwasp with dark blue body and orange legs
Female sirex woodwasp with dark blue body and orange legs. (c) Tania Walisch, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Woodwasps are large, robust, wasp-like insects without a narrow waist, about 1 to 1 1/2 inches long, with a spike at the tail end.[2]
  • Sirex noctilio has a black body and entirely black antennae; females are dark metallic blue with a long egg-laying tube, and most specimens have reddish-brown thighs.[2]
  • Females leave a characteristic drip of resin where they drill through the bark.[2]

Look-alikes

Look-alikeHow to tell them apart
Native horntailsMost native woodwasps attack dead or dying wood and are not major pests; the fungus and venom that kill trees set Sirex noctilio apart.[2]

Where it lives

A female caught in Oswego County, New York, in 2004 first showed it was established in North America; it is now the most abundant woodwasp in pine in northeastern North America. Maryland's Department of Agriculture monitors for it.[1][2]

Biology and life cycle

It usually has one generation a year, sometimes two in cold areas; adults emerge in late summer, live one to two weeks and don't feed.[2]

Females drill through the bark into the sapwood of physiologically stressed pines to lay eggs.[2]

Damage and signs

  • It develops mainly in pines and occasionally in fir, larch, spruce and Douglas-fir.[2]
  • It is considered one of the 10 most serious forest insect pests worldwide and has caused major losses in Southern Hemisphere pine plantations.[1][2]
  • It is commonly detected in wood packing material.[1]

Health risk

None to people or pets.[1][2]

Control

Prevention

Thinning to keep pine stands vigorous and following state rules on moving firewood reduce risk.[2]

Biological control

In the Southern Hemisphere, a parasitic nematode (Deladenus siricidicola) and parasitic wasps are used for biological control.[2]

Common questions

Is the sirex woodwasp in the US?
Yes; an established population was first detected in New York in 2004.[1][2]
How does the sirex woodwasp kill pines?
Females inject a fungus and venom along with their eggs, which can kill stressed trees.[2]
How can I help stop its spread?
Don't move firewood; follow state firewood rules.[2]

Sources

  1. University of Maryland Extension, “Sirex Woodwasp.” extension.umd.edu/resource/sirex-woodwasp (accessed 2026-10-15)
  2. University of Florida IFAS Extension (Featured Creatures), “Sirex Woodwasp, Sirex noctilio (EENY-671).” ask.ifas.ufl.edu/publication/IN1154 (accessed 2026-10-15)
  3. iNaturalist, “Sirex noctilio taxon page (order and family).” www.inaturalist.org/taxa/202629 (accessed 2026-10-06)

Updated 2026-10-15. Built from sourced records. Spot an error? Tell us.