Sirex woodwasp: what the agencies record

This page reports what the official source says. It is not legal advice: ask the office named here. It does not identify what is wrong with any tree and does not say what should be done about one. The Sirex woodwasp, Sirex noctilio, is a large wood-boring wasp from Europe, Asia and northern Africa that attacks pines. Each section names its source, all read on October 9, 2026. The parent page, insect pests of trees, compares it with the other pests on the list.

Origin and where it has spread

The University of Arkansas Division of Agriculture says the wasp is native to Europe, Asia and northern Africa, where it is generally a secondary pest, and that it was accidentally introduced to New Zealand, Australia, Uruguay, Argentina, Brazil, Chile and South Africa. It says that in those Southern Hemisphere countries it attacks pine plantations, mostly of North American species, especially Monterey pine and loblolly pine, and that in South America it has caused upwards of 80 percent mortality in plantations of non-native North American pines. Arkansas says it was first trapped in the United States in the fall of 2004 in New York, and that infested wooden crates, pallets and other wood packaging are the likely route in. Cornell Cooperative Extension says it was found infesting trees in central New York in 2005.

EPPO's Global Database, whose distribution page was last updated February 3, 2026, lists the wasp in the United States as restricted distribution, with New York recorded, Pennsylvania as restricted distribution, and Connecticut, Michigan, Ohio and Vermont as few occurrences. It lists Canada as restricted distribution with Ontario named, and Australia (restricted distribution), New Zealand (widespread) and the United Kingdom (widespread).

Hosts

Arkansas says pines are the main hosts and the insect can complete its life cycle on many pine species, naming among them jack, lodgepole, loblolly, longleaf, ponderosa, Monterey and Scots pine. It says white and red pine have served as hosts in New York, and that the wasp has also been recorded on larch, Douglas-fir, spruce and fir. Cornell lists jack, lodgepole, Monterey, pitch, ponderosa, longleaf, shortleaf, loblolly and slash pine as known North American hosts, says Scots, red and white pine are confirmed hosts in New York and jack pine is recorded in southern Ontario, and adds that all pines are likely susceptible.

Stages and life cycle

Stage	What the sources record
Adult	Arkansas: 1.0 to 1.5 inches long, metallic blue-black; the female has reddish-brown legs and a spike under the abdomen that covers the egg-laying tube; the male has an orange-yellow middle abdomen. Adults do not feed and live up to 12 days. Cornell: adults fly from the beginning of July through September in New York
Eggs	Arkansas: a female lays between 20 and 500 eggs, depending on her size; eggs hatch after a minimum of 9 days or may stay dormant for several months
Larva	Arkansas: creamy white and legless with a dark spine at the rear; 6 to 12 instars over generally 10 to 11 months; tunnels are packed with fine sawdust. Cornell: larvae are found only within the wood
Pupa	Arkansas: near the bark surface for 16 to 21 days

Arkansas says the life cycle can take as little as 10 months but up to two years in cooler climates. It says a female drills into the wood to test the tree, and if the tree is acceptable she lays eggs in a spiral of up to five holes and injects a mucus that is toxic to pines and a fungus, Amylostereum areolatum, which the larvae feed on. Cornell gives the same sequence and adds that a healthy tree with high resin pressure may receive only the fungus and mucus, without eggs.

Signs the sources list

Arkansas says foliage of infested trees first wilts and may change from dark green to light green, yellow and finally red over the three to six months after attack, and that in the northeastern United States some trees wilted and turned brown without the gradual color change. It lists resin beads at the egg-laying sites and notes that uninfested trees may also show resin beads. Cornell lists resin beads along the trunk and round, often grouped exit holes near branch nodes, and says dying and dead trees become apparent in late summer or early fall, with resin flow noticeable from late July. Both sources say adults leave a round exit hole.

Which trees are attacked

The two sources describe the choice of tree differently. Cornell says suppressed, overtopped or otherwise weakened trees are favored, with broken tops, stem damage and multiple stems also listed, and that larger dominant trees are attacked less often. Arkansas says that at low population levels the wasp selects stressed and injured trees, and at high densities it selects healthy ones. Arkansas adds that native North American woodwasps attack only weakened trees, while this species will attack apparently healthy ones. Cornell says that in its native range the wasp is generally a secondary species on dying or weakened trees, but that as an invasive it has caused economic losses where it became established on North American pines. Cornell states that eradication of the pest will not be possible.

Regulated status

EPPO's categorization page lists Canada as a quarantine pest from 2019, China as a quarantine pest from 2021, Paraguay on its A1 list from 1995, Iran on its A1 list from 2018, Türkiye on its A1 list from 2016 and the COSAVE regional body on its A2 list from 2018. Neither extension source names a quarantine for the United States. For where to send reports of unfamiliar pests, see the guides for the United States and Canada.

Management as the sources list it

Both extension sources tie risk to tree vigor and stand condition: Arkansas says treatments aimed at tree vigor and forest health may help reduce the impact, and Cornell describes overstocked stands with suppressed trees as more likely to be colonized. This page gives no stand-treatment steps or timings. Arkansas directs readers to the Arkansas State Plant Board or the county Extension office for more information.