Amylostereum complex

amylostereum complex damage, caused by sirex woodwasp
Amylostereum complex – Sirex noctilio F.

The woodwasp, Sirex noctilio, and the associated pathogenic fungus, Amylostereum areolatum, are native to Eurasia and North Africa (USDA APHIS & Forest Service 2000) and have been introduced in New Zealand, Australia, South America (USDA Forest Service 1992), and North America (Lang 2006; USDA APHIS 2007; Canadian Forest Service 2005). The woodwasp was caught in a trap in New York in 2005, but not identified until early 2006. The woodwasp is now present across much of New York State, parts of Ontario, and neighboring areas such as eastern Michigan, northern Pennsylvania, and a few counties in Ohio and Vermont. In the upper Midwest, wood could jeopardize decades of careful management of Jack pine (Pinus banksiana) stands aimed at ensuring survival of the highly-endangered Kirtland’s warbler. Federal and state agencies spend about $2.5 million annually to manage Jack pine stands in Michigan to the benefit of the warbler (Hogrefe pers. comm.).

The woodwasp injects fungus in the tree when the female lays her eggs. This insect-disease complex would threaten any pine trees in the lower 48 states, especially Monterey pine (P. radiata) and loblolly pine (P. taeda), as plantations of these species growing in foreign countries have been severely damaged (USDA APHIS & Forest Service 2000). Other pines that are highly vulnerable to the Sirex woodwasp are other species in the Southeast (shortleaf, slash, and Virginia pines—P. echinata, P. elliottii, P. virginiana), midwest (Jack pine), and across the West (lodgepole, ponderosa, and Jeffrey—P. contorta, P. ponderosa, P. jeffreyi). (USDA APHIS 2007). In New York, the woodwasp has attacked pine (P. sylvestris L.), red pine (P. resinosa), and white pine (P. strobus).

All important softwood timber trees of the southeast vulnerable to the woodwasp. According to the USDA Forest Service, if no action is taken to contain the woodwasp, it could spread across the entire southern pine region in 55 years or less (USDA Forest Service 2006). The resulting damage could range from $2 billion to $11 billion.

Before the woodwasp outbreak was discovered, experts were aware that its larvae are often found in solid wood packing material or other wood articles shipped from both its native and introduced ranges (Tribe 1995); the insect has commonly been intercepted by APHIS inspectors. The woodwasp can spread rapidly by natural means (USDA Forest Service 1992).

A control agent (the parasitic nematode Beddingi(=Deladenus) siricidicola) been applied by the Southern Hemisphere countries as part of integrated management programs that also include stand management (Pfister pers. comm. February 2010). APHIS scientists have been utilizing the nematode for both its ability to survive the winter and its host specificity. (Williams 2008; Williams 2009).

Application of biocontrol to protect pines in the Southeast or West will be complicated. The woodwasp infestation’s leading edge must be tracked carefully as the leading edge is the location where biocontrol application will prove most effective in preventing both spread and damage– and so far detection technology is imprecise. The biocontrol program must be coordinated with active silvicultural management of the pine stands. The ability of the nematode to reduce woodwasp numbers can be impeded by tree mortality due to drought or attacks by other insects, and by the presence of bluestain fungi. American pines are regularly attacked by other insects and bluestain fungi are common here. Finally, care is needed in selection of the strain of nematodes, rearing conditions, and techniques for inoculation of trees

Adoption of federal and state regulations governing movement of known or potential vectors for moving the woodwasp to other parts of the country has been delayed by lack of funding for a control program and disagreements within USDA over the proper form for the regulations (Dunkle, pers. comm.). In FY2009, Congress for the first time provided funding for the program – $1.5 million; but this is not sufficient to support a regulatory program. Funding is instead being used for detection and monitoring of woodwasp populations and further testing of the biocontrol agent. North Carolina has adopted its own external quarantine to protect its vulnerable pine resource.

USFS scientists and managers developed a conservation priority-setting framework for forest tree species at risk from pest & pathogens and other threats. The Project CAPTURE (Conservation Assessment and Prioritization of Forest Trees Under Risk of Extirpation) uses FIA data and expert opinion to group tree species under threat by non-native pests into vulnerability classes and specify appropriate management and conservation strategies. The scientists prioritized 419 tree species native to the North American continent. The analysis identified 15 taxonomic groups requiring the most immediate conservation intervention because of the tree species’ exposure to an extrinsic threat, their sensitivity to the threat, and their ability to adapt to it. Each of these 15 most vulnerable species, and several additional species, should be the focus of both a comprehensive gene conservation program and a genetic resistance screening and development effort.  The woodwasp, Sirex noctilio is not known to be a threat to any of these 15 most vulnerable species. 


Canadian Forest Service. 2005. Forest Health Update. Sirex woodwasp Sirex noctilio F. November 30.

Lang, S.S. 2006. Invasive wasp, Southern Hemisphere forest devastator, found to be “well-established” in upstate New York. Cornell Chronicle Online. February 24.

Michigan Department of Agriculture. 2007. New Invasive Insect Confirmed in Michigan. July 16.

Potter, K.M., Escanferla, M.E., Jetton, R.M., Man, G., Crane, B.S., Prioritizing the conservation needs of US tree spp: Evaluating vulnerability to forest insect and disease threats, Global Ecology and Conservation (2019), doi:

Tribe, G. D. 1995. The woodwasp Sirex noctilio Fabricius (Hymenoptera: Siricidae), a pest of Pinus species, now established in South Africa. African Entomol. 3: 215-217.

United States Department of Agriculture Animal and Plant Health Inspection Service and Forest Service 2000. Pest Risk Assessment for Importation of Solid Wood Packing Materials into the United States. USDA APHIS and Forest Service. August 2000.

USDA Agriculture Animal and Plant Health Inspection Service. 2007. Organism Pest Risk Analysis: Risks to the Conterminous United States Associated with the Woodwasp, Sirex noctilio Fabricius, and the Symbiotic Fungus, Amylostereum areolatum (Fries: Fries) Boidin. May 2007

United States Department of Agriculture Forest Service. 1992. Pest Risk Assessment of the Importation of Pinus radiata and Douglas-fir Logs from New Zealand, Miscellaneous Publication No. 1508, October 1992.

United States Department of Agriculture Forest Service. 2006. Economic Analysis of the Potential Impact of Sirex noctilio, With Emphasis on Pines in the Southeastern United States. January 2006.

Williams, D. 2008. 19USDA Interagency Research Forum on Invasive Species. Annapolis, MD. January 8-11, 2008.

Williams, D. 2009. 20th USDA Interagency Research Forum on Invasive Species. Annapolis, MD. 13-16, 2009.