Agriculture and Natural Resources

FSA7071

Invasive Woodwasp, Sirex noctilio: APotential Pest of Pines in Arkansas

The Sirex woodwasp, Sirex noctilio production is greater than $8 billion John D. Hopkins Fabricius (Hymenoptera:Siricidae), per year (USDA, APHIS, 2006a). Assistant Professor and is an exotic wood­boring insect that Even­aged pine stands and/or Extension Entomologist serves as a vector for the disease stressed pine trees are particularly at fungus, Amylostereum areolatum. risk. However, because North Together, this exotic wasp and American native pine ecosystems are Tamara Walkingstick Associate Professor and fungus can colonize a wide range of more diverse and complex than pine

Forest Extension North American pines and cause plantations in South America and

Specialist considerable tree mortality. Australia planted with southern North American species, predicting

Jim Lee Wallace the impact of S. noctilio is difficult. Invasiveness and Pest State Survey Coordinator Potential Silvicultural treatments aimed In South America, the insect has at maintaining tree vigor and forest caused upwards of 80 percent mortality health may help reduce the impact in plantations planted with non­native of S. noctilio on pine forests. North American pine species. In the Physiological stress factors, including fall of 2004, S. noctilio was trapped for storm damage, drought, competition the first time in the United States in and defoliators, can predispose trees New York state (Hoebeke et al., 2005) to attack by insects, including S. noc­ and has subsequently been found in a tilio. Maintaining tree health may number of counties in New York and reduce the risk to attack. However, Pennsylvania and adjacent areas in S. noctilio females will also oviposit Ontario, Canada. The mode of introduc­ into healthy trees, stressing the trees tion into the United States is likely to and predisposing them to future be through importation of infested attacks (Thayer, 2007, USFS, 2006). wooden crates, pallets and other wood packaging. S. noctilio is native to Europe, Asia and northern Africa, where it Although not discovered in the is generally considered to be a southern states yet, this exotic insect secondary pest. It was inadvertently pest poses a potential threat to the introduced into New Zealand, southeastern forest products indus­ Australia, Uruguay, Argentina, try, especially because all southern Brazil, Chile and South Africa. In pine species are vulnerable to attack. these Southern Hemisphere coun­ Softwood production in the United tries, S. noctilio attacks exotic pine States is a multibillion dollar indus­ plantations, most of which are Arkansas Is try that provides numerous commodi­ planted with North American pine ties. In the southern states where species, especially Monterey pine Our Campus pine production typically occurs in (Pinus radiata) and loblolly pine large, even­aged, managed stands, (P. taeda). Pines are the main hosts the combined value of logs and bolts, of S. noctilio, and the insect can

Visit our web site at: lumber, veneer and pulpwood complete its life cycle on numerous

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University of Arkansas, United States Department of Agriculture, and County Governments Cooperating species within the pine genus is a spike­like projection which (Pinus), including P. attenuata, protects the ovipositor (egg­laying P. banksiana, P. brutia, tube) when not in use. The middle P. calabrica, P. canariensis, segments of the abdomen in the P. caribaea, P. contorta, P. densi­ adult male are orange­yellow, and flora, P. echinata, P. elliotii, the hind legs are thickened and P. halepensis, P. jeffreyi, P. muri­ almost wholly black. cata, P. nigra austriaca, P. nigra, Larvae are creamy white, leg­ P. palustris, P. patula, P. pinaster, P. pinea, P. ponderosa, P. radiata, less and have a distinctive dark P. sylvestris and P. taeda spine at the rear of the abdomen. (Appendix A; USDA, APHIS, S. noctilio can go through its 2006a). In the United States (New life cycle in as little as 10 months York), P. strobus (white pine) and but may take up to two years in P. resinosa (red pine) have served cooler climates. Males emerge as hosts for S. noctilio. Also, S. noctilio has been recorded on before the females. Male S. noctilio other conifers, such as larch (Larix engage in lekking behavior, in spp.), Douglas fir (Pseudotsuga which they fly in single­sex menziesii), spruce (Picea spp.) and swarms around the tops of trees; fir (Abies spp.). individual females fly into these leks to mate. Females that do not A prediction model for the mate lay eggs that produce all potential distribution of S. noctilio males, whereas mated females in North America found that many produce offspring of both sexes. areas of the United States, Canada Females can begin to lay eggs and Mexico were suitable for one day after adult emergence. establishment (Carnegie et al., 2006). S. noctilio can tolerate the Adults do not feed; instead, they climates found within the United live on fat stored in their bodies. States, and thus, APHIS expects The adult life span can last up to that the absence of suitable host 12 days, but females that deposit pines will probably be the factor all their eggs may survive for an most limiting the distribution of S. additional three to four days. noctilio. S. noctilio can likely Throughout their short life, establish wherever pines are found females deposit between 20 and in North America. 500 eggs, depending on the size of the female (larger females Native species of siricid generally lay more eggs). woodwasps are present in many ecosystems in North America, but In preparation for egg these native woodwasps differ deposition, females land on trees, from S. noctilio in that this non­ drill into the wood and assess the native species will attack appar­ suitability of the tree for oviposit­ ently healthy trees, whereas native ing. If the tree is unacceptable for siricids only attack trees that have oviposition, the female will fly to been weakened (USFS, 2005). another tree. If the tree is accept­ able, she lays a single egg and

Description and Biology then continues to move upward in a spiral pattern, drilling up to of Sirex noctilio four more holes and depositing The Sirex woodwasp is a the remainder of her eggs. relatively large insect, ranging Females, after ovipositing in one from 1.0 to 1.5 inches long, with metallic (iridescent) blue­black tree, may move on to additional body coloration. The adult female trees as long as their eggs and is steel­blue except for reddish­ energy reserves hold out. Mucus brown legs. Pointing backwards that is toxic to pine trees is from the underside of the abdomen injected during drilling. The mucus causes the foliage to wilt Larvae hatch from the eggs hole, which varies in diameter and yellow, creating ideal condi­ after a minimum of 9 days; how­ according to the size of the wasp. tions for the spread of fungus. The ever, the eggs may remain dor­ last hole is packed with spores of mant for several months, At low population levels, S. noctilio selects stressed and a fungus (Amylostereum areola­ overwintering in cooler climates. injured trees for egg laying; how­ tum). The fungus causes the wood The number of larval instars ever, at high population densities, to dry out, thereby creating a varies from 6 to 12, and the larval S. noctilio will select healthy trees. more favorable environment for stage generally takes 10 to 11 Foliage of infested trees initially egg hatching. After hatching, the months. Larval tunnels created in wilts and then may change color S. noctilio larvae feed on this fun­ the wood are tightly packed with from dark green to light green to gus. These effects together may very fine sawdust. Mature larvae yellow and finally to red during kill the tree. pupate close to the bark surface. The pupal stage lasts between 16 the three to six months following and 21 days. When a female wasp attack. In the northeastern United emerges from her pupal skin, she States, some trees struck by S. takes up fungal spores from the noctilio have wilted and the nee­ tree from which she emerges and dles have turned brown without stores them in a special organ in the gradual color change. Infested her abdomen. The adult wasp trees may have resin beads or bores its way out of the tree, leav­ dribbles at the egg­laying sites, but ing a characteristic round exit uninfested trees may also exhibit resin beads and dribbles as well.

Contact the Arkansas State Plant Board (501­225­1598) or your local county Extension office for more information.

Photo credits: Dennis A.

Haugen, USDA Forest

Service, Forest Health

Protection, St. Paul, MN.

References Carnegie, A.J., M. Matsuki, D.A. Haugen, B.P. Hurley, R. Ahumada, P. Kklasmer, J. Sun and E.T. Iede. 2006. Predicting the potential distribution of Sirex noctilio (Hymenoptera:Siricidae), a significant exotic pest of Pinus plantations. Annals of Forestry Science. 63:119–128. Hoebeke, E.R., D.A. Haugen and R.A. Haack. 2005. Sirex noctilio: Discovery of a Palearctic siricid woodwasp in New York. Newsletter of the Michigan Entomological Society 50(1&2):24­25. Thayer, Charles L. 2007. United States Associated with U.S. Forest Service, Northeastern Amylostereum areolatum (Fr.) the Woodwasp, Sirex noctilio Area State and Private Boidin Sirex­Fungus: Pest Fact Fabricius, and the Symbiotic Forestry. 2005. Pest Alert, Sirex Sheet. U.S. Department of Fungus, Amylostereum areola­ woodwasp – Sirex noctilio F. Agriculture, Animal & Plant tum (Fries:Fries) Boidin. July, (Hymenoptera: Siricidae). Health Inspection Service. 2006. Raleigh, NC. NA–PR–07–05, June, 2005. http://www.aphis.usda.gov/plant USDA, APHIS, 2007. Proposed U.S. Forest Service. 2006. Southern _health/plant_pest_info/sirex/ Program for Management of Forest Health and Research downloads/sirexfungus.pdf. the Woodwasp Sirex noctilio Update, Sirex noctilio in North Accessed date 11/20/2007. Fabricus (Hymenoptera: America. Summer 2006, Vol. 1, U.S. Department of Agriculture, Siricidae). Environmental Issue 1: http://www.fs.fed.us/ Animal and Plant Health assessment. http://www.aphis. r8/foresthealth/publications/ Inspection Service. 2006a. usda.gov/plant_health/ea/ southern_fhp_research_update/ Organism Pest Risk Analysis: downloads/sirex­ea.pdf. summer2006_vol1_1.pdf. Risks to the Conterminous Accessed date 11/06/2007. Accessed Date 11/20/2007.

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DR. JOHN D. HOPKINS is Assistant Professor and Extension Issued in furtherance of Cooperative Extension work, Acts of May 8 and Entomologist with the University of Arkansas Division of Agriculture, June 30, 1914, in cooperation with the U.S. Department of Agriculture, Cooperative Extension Service, Little Rock. DR. TAMARA Director, Cooperative Extension Service, University of Arkansas. The WALKINGSTICK is Associate Professor and Forest Extension Arkansas Cooperative Extension Service offers its programs to all Specialist with the University of Arkansas Division of Agriculture, eligible persons regardless of race, color, national origin, religion, Cooperative Extension Service, Little Rock. JIM LEE WALLACE is gender, age, disability, marital or veteran status, or any other State Survey Coordinator with the Arkansas State Plant Board, legally protected status, and is an Affirmative Action/Equal Little Rock. FSA7071­PD­1­08N Opportunity Employer.