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Sirex Woodwasp

French Common name: Grand hylésine des pins
Scientific name:  Sirex noctilio 
Order: Hymenoptera
Family: Siricidae

The Sirex Woodwasp (SWW; Sirex noctilio), native to Eurasia and Africa, was likely introduced to North America through wood packing material. The first detection of SWW was in the state of New York close to Lake Ontario in 2004 (Hoebeke et al., 2005).  SWW was found in Canada in 2005 (de Groot et al., 2006). The SWW is currently widespread throughout the Northeastern United States, and can be found in portions of southern Ontario and Quebec.

The SWW favours scots pine (Pinus sylvestris), a non-native tree species that is widespread in Northeastern North America. SWW is considered a serious threat to pine plantations as it can attack both healthy and stressed trees, although impacts have so far been limited in North America. Studies suggest that proper forest management can be effective at controlling the impacts and spread of this invasive pest.

Quick Tips:

-   Look for resin drops at the mid-bole (mid-trunk) level where they are commonly found after oviposition of SWW females.

-   Do not move firewood

Learn About the Sirex Woodwasp

The Insect

Physical Description

 sausage-shaped and white in colour.

Larvae: legless and creamy to yellowish white in colour. Larvae can reach about 30 mm long and have a visible spine (needle) towards the rear end of the body.

Pupae: initially creamy-white in colour, but gradually takes on the colour of the adult.  

Photo: Vicky Klasmer, Instituto Nacional de Tecnologia Agropecuaria, Bugwood.org 
Photo: William M. Ciesla, Forest Health Management International, Bugwood.org
Detail of the characteristic tailspine   Male pupa and gallery 

Adults: dark bodies and orange legs. Males have a metallic blue head and thorax, with an orange abdomen and front legs. Females have a metallic blue head and body with orange legs. In addition, females also have a spine (needle) at the end of the abdomen. Both the male and female SWW have a cylindrical body and a pointed abdomen.

Photo: Steven Valley, Oregon Department of Agriculture, Bugwood.org

Photo: Steven Valley, Oregon Department of Agriculture, Bugwood.org

 Sirex noctilio female lateral  Sirex noctilio male


Life Cycle

The lifecycle of SWW, from egg to adult, takes one to two years to be completed depending on climate conditions. Adult SWW can be found between July and September in Quebec and southern Ontario. Female SWWs drill holes into the outer sapwood and lay eggs.  Depending on its size, a female lays 25-450 eggs in its lifetime.  With the eggs, the SWW injects spores of the fungus Amylostereum areolatum and a toxic mucus.  The fungus and the mucus weaken the tree, aiding larval development.  The larvae go through 6-12 instars, over a period of 10-11 months. The variation in the number of instars may be related to host tree suitability. Mature larvae pupate close to the surface of the bark, and adults usually emerge after three weeks. Adult SWW survive off of resources acquired as larvae, reproduce and die within 3-4 days.

Host Trees

Unlike native woodwasps in Canada which only attack stressed trees, the SWW also attacks healthy trees. When SWW populations are low, they tend to attack trees that are dead or dying, but attack healthy trees as their numbers increase. 

Potential SWW hosts include:

Pine species (Pinus) - main host
-  Spruce (Picea),
-  Fir (Abies),
-  Larch (Larix),
-  Douglas fir (Pseudotsuga).

Many of these potential host species occur in plantations throughout Canada, and are threatened by the SWW. 

Signs and Symptoms

Signs and symptoms of SWW include:  

  • Resin dripping from oviposition sites (places on the trees where eggs are laid) mainly concentrated in the mid-bole (mid-trunk) level of the attacked tree

  • Wilted foliage ranging from yellow to reddish -brown in colour.

  • Larval galleries found under the bark. The galleries are usually packed with frass (insect excrement) and chewed wood.

  • Round exit holes ranging between 3 and 8 mm in diameter on the bark of the tree trunk.

  • Heavily infested trees usually die.

Photo: Dennis Haugen, Bugwood.org Photo: Vicky Klasmer, Instituto Nacional de Tecnologia Agropecuaria, Argentina,Bugwood.org Photo: Dennis Haugen, Bugwood.org
Round exit holes Sirex Woodwasp Damage Resin drops from oviposition wounds


The SWW is native to Asia, Europe and Africa. It has been introduced to Canada, the U.S. as well as New Zealand, Australia, Uruguay, Argentina, Brazil, Chile, China and South Africa.

In 2005, SWW was found only in a few locations in southern Ontario but by 2010 it had expanded its range to cover almost all of southern Ontario reaching as far north as Manitoulin Island and was also in part of Quebec.  In the United States, as of 2011, the SWW has been confirmed in portions of New York, Pennsylvania, Vermont, Connecticut, Ohio, and Michigan.  



Since SWW has been recently introduced to Canada, studies about the complex interactions among insect spread and tree mortality are ongoing.  Initial studies show that the SWW prefers weak trees with a small diameter over healthy, large ones and that silvicultural treatments may be effective at managing SWW populations and minimizing its impact (Dodds, et al., 2010). 

Photo: Stanislaw Kinelski, Bugwood.org 

SWW damage to Scots pine 

Economic Impacts

Commercial industries surrounding pine trees are threatened.  The mucus causes foliage to yellow and wilt while the fungus disrupts water movement; the combined effect of both the mucus and fungus often kills the host trees, depending on their condition and resistance, and assists the development of the SWW larvae (GISD, 2017). The United States Department of Agriculture Forest Service estimates that if the SWW becomes established nationwide, it would cost about $2.8 - $17 billion in lost timber and pulpwood (NYIS). A study published in 2008 by Yemshanov, et al. estimated the possible physical and economic impacts of SWW on standing pine biomass in eastern Canada. The study projected medium term losses of up to $254.1 million per year after 20 years (at time of publishing) in Ontario and Quebec (Yemshanov, et al., 2008).

Ecological Impacts

The SWW has the potential to negatively impact wildlife, especially species that are dependent on pine trees as a habitat or food source. For example, the success of the endangered Kirtland’s warbler depends on sufficient jack pine habitat. In Michigan alone, federal and state agencies spend about $2.5 million yearly to manage jack pine stands for the endangered Kirtland’s warbler (Campbell, 2007). SWW could jeopardize this effort, and contribute to the species’ decline.

Photo: Joel Trick/USFWS

Male Kirtland’s warbler from Adams country,Wisconsin

It is important to note that economic loss could vary depending on the interactions among the insect, tree mortality, and forest harvest schedule (NRCan, 2012).

Social Impacts

SWW host trees in many places are an important part of the landscape’s integrity, aesthetics, and recreational value. 



The currently available monitoring traps and semiochemical combinations are considered to be generally ineffective (NRCan, 2012). A study by Haavik, et al. (2014) suggests that efficacy of traps could be improved with the use of different lures. Semiochemical baited traps are known to attract SWW, but an effective combination of attractants is yet to be determined (Boroczky et al. 2009, 2012; Cooperband et al., 2012 as cited in Haavik et al., 2014).

Respond & Control 

Silvicultural management can effectively prevent or mitigate the impacts of a SWW infestation (Dodds, et al., 2010). Silvicultural management practices such as thinning a forest to minimize overcrowding, removing weakened or dying trees, and routine surveillance have been proven effective in mitigating the attacks of SWW in North America (Dodds at al., 2014). 

Photo: Dennis Haugen, Bugwood.org

Silvicultural control: there is no apparent mortality in thinned section shown in the upper right corner of the photo

Chemical control for the SWW seems to be an option of concern due to the potential impacts on the environment and other organisms. There are no known effective compounds that are used for control SWW chemically.


The parasitic nematode, Deladenus siricidicola, has been found to be a successful biological control agent for the SWW in the southern hemisphere (Texas invasive species institute, 2014). The nematode sterilizes female wasps, causing them to lay infertile eggs and to spread the nematode populations wherever the eggs are laid. This nematode has been found in SWW in Canada (NRCan, 2012), but the strain is non-sterilizing in North America because it does not penetrate eggs (Yu et al. 2009 as cited in Haavik et al, 2016).  

A native parasitic wasp, Ibalia leucopsoides, has been found to expand its host range to include SWW (NRCan, 2012). Studies are ongoing to identify SWW natural enemies in Canada and their effects on SWW populations.

Photo: Ethan Angell, New York State Department of Agriculture & Markets, Bugwood.org Photo: William M. Ciesla, Forest Health Management International, Bugwood.org

 Ibaliid wasp (Ibalia leucospoides)
Culture of parasitic nematode




About the Sirex Woodwasp. Retrieved from http://hamiltoncs.org/forever-wild/sirex-noctilio/about-the-sirex-woodwasp/ on 01/12/2016

Borocaky, K., Zylstra, K. E., McCartney, N. B., Mastro, V. C., and Tumlinson, J.H. (2009) Monoalkenes as contact sex pheromone components of the woodwasp Sirex noctilio. Journal of Chemical Ecology. 35: 1202-1211.

Borocaky, K., Crook, D. J., Jones, T. H., Kenny, Zylstra, K. E., Mastro, V. C., and Tumlinson, J.H. (2012) Volatile profile differences and the associated Sirex noctilio activity in two host tree species in the Nothereastern United States. Journal of Chemical Ecology. 38: 213-221.

Campbell, F. (2007). | Woodwasp-Amylostereum complex. The Global Invasive Species Team. Retrieved from https://www.invasive.org/gist/products/gallery/sirno1.html on 12/06/2016

Campbell, F.(2010).Sirex Woodwasp Amylostereum complex - Sirex noctilio F. Retrieved from http://www.dontmovefirewood.org/gallery-of-pests/woodwasp.html on 28/11/2016

CFIA.(2012). Sirex noctilio (Sirex woodwasp) - Fact Sheet. Retrieved from http://www.inspection.gc.ca/plants/plant-pests-invasive-species/insects/sirex-wasp/fact-sheet/eng/1327690769701/1327690933257 on 28/11/2016

Cooperband, M. F., Boroczky, K. Hartness, A., Jones, T. H., Zylstra, K.E., Tumlinson, J.H  and Jones, G. H.(2012). Male-produced pheromone in the European woodwasp, Sirex noctili. Journal of Chmical Ecology. 38: 52-62.

de Groot, Nystrom, L.K., Scarr, T.A. (2006). Discovery of Sirex noctilio (Hymenopetra: Siricidae) in Ontario, Canada. Grt. Lks. Entomol. 39: 49-53.

Dodds, K.J, Cooke, R.R., and Hanavan, R.P. (2014). The effects of silvicultural treatment on Sirex noctilio attacks and tree health in northeastern United States. Forests, 5, 2810-2824

Dodds, K.J., de Groot, P., Orwig, D.A. (2010). The impact of Sirex noctilio in Pinus resinosa and Pinus sylvestris stands in New York and Ontario. Can. J. For. Res. 40: 212-223.

Global Invasive Species Database (2017) Species profile: Sirex noctilio. Downloaded from http://www.iucngisd.org/gisd/species.php?sc=1211 on 07-03-2017 [Accessed 1st September 2005].

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Haavik, J. L., Batista, E., Dodds, J. K., Johnson, W., Meeker, E. J., Scarr, A. T., and Allison, D, J. (2014). Type of Intercept Trap Not Important for Capturing Female Sirex noctilio and S nigricornis (Hymenoptera: Siticidae) in North America. Journal of Economic Entomology. 107 (3) : 1295 – 1298.

Haavik, L., Dodds, J. K., and Allison, D. J. (2015). Do Native Insects and Associated Fungi Limit Non-Native Woodwasp, Sirex noctilio, Survival in a Newly Invaded Environment?. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4598122/pdf/pone.0138516.pdf on 29/11/2016

Haavik, L., Dodds, J. K., and Allison, D. J. Suitability of Eastern Pines for Oviposition and Survival of Sirex noctilio F. 

Haavik, L., Dodds, J. K., Ryan, K., and Allison, D. J. (2016). Evidence that the availability of suitable pine limits non-native Sirex noctilio in Ontario. Agricultural and Forest Entomology, DOI: 10.1111/AFE. 12167

Hoebeke, E.R., Haugen,  D.A. and  Haack, R.A. (2005). Sirex noctilio: Discovery of a palearctic siricid woodwasp in New York. Newslett. Mich. Ent. Soc., 50: 24-25.

Natural Resources Canada. (2012). Bulletin 59: Population of a non-indigenous woodwasp found in pine trees in Ontario. Canadian Forest Service - Great Lakes Forestry Centre. Retrieved from http://publications.gc.ca/collections/collection_2013/rncan-nrcan/Fo122-1-59-2012-eng.pdf on 29/11/2016 

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Yemshanov, D., McKenney, D. W., de Groot, P., Haugen, D., Sidders, D., and Joss, B. (2008). An Assessment of Sirex Noctilio Spread and Potential Impacts on Pine Wood Supply and Harvests in Eastern Canada. USDA Research Forum on Invasive Species.