Taxonomic name: Sirex noctilio (Fabricius, 1793)
Common names: avispa barrenadora de los pinos (Spanish), avispa taladradora de la madera (Spanish), Blaue Fichten (German-Germany), European woodwasp (English), Holzwespe (German-Germany), horntail (English), sartfottreveps (Norwegian-Norway), sirex (Portuguese), Sirex wasp (English), Sirex woodwasp (English), sortfodet træhveps (Danish-Denmark), steel blue (English), steel-blue (English), svartfotad vedstekel (Swedish-Sweden), vespa-da-madeira (Portuguese), wood wasp (English), woodwasp (English)
Organism type: insect
Sirex noctilio (or Sirex woodwasp) is a high risk invasive species native to Europe and parts of Asia that has proven devastating to many commercial pine plantations, with mortality rates as high as 80%. It is capable of inflicting billions of dollars in damages. International, national and state agencies have conducted much research on Sirex noctilio and remain focused on its control and containment.
Sirex noctilio is a Siricid woodwasp, or Horntail. Adults have a long cylindrical body lacking the typical narrow petiole "waist", two sets of transparent wings, and a spear-shaped plate (cornus) at its tail. Females are generally larger measuring about 15-35mm long, having a metallic blue head and body, orange legs, and a pointed projection at the tail to protect the ovipositor. Males measure about 13-32mm and have a metallic blue head and thorax, an orange abdomen with a dark tip, and orange front and thickened, black rear legs. Larvae are creamy white with a cylindrical body, identifiable head, three pairs of short legs and a spine at the posterior end (Zondag, 1977; King, 2005).
Please see PaDIL (Pests and Diseases Image Library) Species Content Page Wasps: Sirex woodwasp for high quality diagnostic and overview images.
natural forests, planted forests
The female sirex woodwasp bores deep into living trees and deposits eggs with its ovipositor along with a symbiont fungus (Amylostereum areolatum) and toxic mucus. The mucus inhibits the defences of the tree, allowing the white rot fungus to grow. The larvae then bore galleries throughout the tree, feeding on the fungus. Sirex noctilio is primarily attracted to stressed, sick, and suppressed trees with intermediate moisture content. Some softwoods (conifers) and all species of pine are believed to be at risk of infestation (Madden, 1974; Madden, 1981; NYSDEC, 2007).
Sirex noctilio along with its obligate symbiotic fungus Amylostereum areolatum pose a serious threat to the pine industry. It has been known to devastate pine stands causing as much as 80% mortality. The USDA Animal and Plant Health Inspection Service (APHIS) added S. noctilio to its Regulated Plant Pest List and it was rated a "very high risk" pest in pest risk assessment for North America. In its native ranges, S. noctilio is considered a secondary pest. Expansive monoculture tree plantations, favourable climate, and lack of natural predators and hyperparasites render invasive ranges highly susceptible to infestation. The sirex woodwasp lays its larvae in conifers primarily Pinus spp. along with its symbiotic fungus A. areolatum and a toxic mucus which facilitates the growth of the fungus. The mucus causes foliage to wilt and yellow, providing good conditions for A. areolatum to grow and spread throughout the tree. The fungus causes the tree to dry out by disrupting water movement. The combined effect of the mucous and fungus most often kills the tree.
Even if the host tree survives, its wood is often degraded value because of resin accumulations or killed zones. Healthy trees are known to resist oviposition by flooding holes with resin or by producing polyphenols that prevent fungal growth. Understandably, ovipositing S. noctilio females prefer stressed trees. Research indicates that their sensillae, inner surfaces of the valvulae (sensory receptors on the ovipositor) are capable of determining the tree's levels of resin and moisture content. As they prefer intermediate to low moisture and will withdraw their ovipositor if they pierce a resin duct. S. noctilio almost always attacks trees stressed by factors such as drought, overcrowding, physical damage, unrelated fungal infection, or simply inundation with other ovipositions. Infested trees are identifiable by yellow or reddish-brown tree crowns, beads of resin dripping down the bark from oviposition sites, larval tunnels and frass in the wood, and exit holes 3-8mm in diameter. All species of Pinus are considered viable hosts as well as some members of genera Abies, Larix, Picea, and Pseudotsuga. Notable host species include: Monterey pine (Pinus radiata), loblolly pine (Pinus taeda), slash pine (Pinus elliottii), Scots pine (Pinus sylvestris), Austrian pine (Pinus nigra), maritime pine (Pinus pinaster), Eastern white pine (Pinus strobus), ponderosa pine (Pinus ponderosa), red pine (Pinus resinosa), Mexican pine (Pinus patula), jack pine (Pinus banksiana), Carribbean pine (Pinus caribaea), lodgepole pine (Pinus contorta), shortleaf pine (Pinus echinata), longleaf pine (see Pinus palustris in IUCN Red List of Threatened Species), pitch pine (Pinus rigida), Jeffrey pine (Pinus jeffreyi), and Chiapas white pine (Pinus chiapensis) (Zondag, 1977; APHIS, 2007; Bean, 2005; Morgan, 1968; Wingfield, 2001; Pollard, 2006).
Native range: Austria, Belgium, Canarias (Spain), Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Mongolia, Norway, Poland, Portugal, Romania, Russian Federation, Serbia and Montenegro, and United Kingdom
Known introduced range: Argentina, Australia, Brazil, Canada, Chile, New Zealand, South Africa, United States, Uruguay
Introduction pathways to new locations
Natural dispersal: Sirex noctilio is a strong flyer typically moving about 25 miles per year. However, some have reported it as capable of flying 100 miles (SSPR, 2006; Bean, 2005).
Transportation of habitat material: Sirex noctilio larvae and pupae may be transported along with timber, logs, and untreated lumber in any form thicker than 2.5 cm. Wooden packaging such as wooden crates, pallets, blocks, load boards, etc. is cited as a probable means of introduction to new locations (Davies, 2006; Keiran, 2004).
Local dispersal methods
Natural dispersal (local): Sirex noctilio is a strong flyer typically moving about 40 km. However, some have reported it as capable of flying 160 km (SSPR, 2006; Bean, 2005).
Transportation of habitat material (local): Sirex noctilio may also be dispersed locally by trasnport of timber, logs, and untreated wood products (Davies, 2006).
Preventative measures: Sirex noctilio is a high risk invasive species and many actions have been taken to prevent its spread. Restrictions on the movement of timber and firewood have been imposed in most invasive ranges. The USDA APHIS (Animal and Plant Health Inspection Service) inspectors remain vigilant and have successfully intercepted foreign siricids in international US ports on over 100 occassions. APHIS also has a Plant Protection and Quarantine (PPQ) division which is working hard to prevent further spread in the US by informing the public and wood industry and conducting extensive trapping surveys.
In 2002, United Nation FAO's (Food and Agriculture Organization) Interim Commission on Phytosanitary Measures imposed a global standard for treating wood packaging International Standard for Phytosanitary Measures No. 15 to stop the spread of invasives including S.noctilio. Although, implementation has proven difficult. Similarily, New York State the Department of Conservation has imposed recommended treatment protocols for all wood products over 2.5cm thick. Silvicultural management is another important means of preventing S. noctilio infestation. Since, the Sirex woodwasp attacks stressed trees, healthy and vigorous trees properly maintained by good silviculture practice, including routine survelliance, pruning, and appropriate watering and spacing of trees, will assist in preventing new infestations and to control present populations. Recently, aerial multispecteral imagaing technology has been employed to detect infected trees in large pine plantations of KwaZulu-Natal, South Africa. Another use of technology employs computer modeling by programs like CLIMEX to render a predictive modeling of potential invasive ranges (Hoebeke, 2005; NAPPO, 2007; Keiran, 2005; NYSDEC, 2006; Fernandez-Ahrex, 2005; Ismail, 2007; Carnegie, 2006).
Biological: Biological control agents have been the most popular and successful means of managing Sirex noctilio. Many species of parasitic wasps have been employed including: Megarhyssa nortoni, Rhyssa persuasoria, Rhyssa hoferi, Ibalia leucospoides, and Schlettererius cinctipes. Of these M. nortoni, R. persuasoria, and I. leucospoides have been the most effective, employed in New Zealand, Australia, South America, and South Africa. These wasps find S. noctilio larvae, then bore into the tree, paralyze them, and deposit their eggs on them. Sirex larvae are then consumed by the newly hatched parasite larvae. However, the most effective means of control has been from parasitic nematode Deladenus siricidicola (also =Beddingia ). This nematode has an almost perfectly designed life cycle to control Sirex woodwasps. Its first stage feeds on fungus Amylostereum areolatum while the second invades the larvae collecting in their reproductive organs. Females are sterilized while males spread the nematode further. This agent has been successful in South America, South Africa, Australia, and especially New Zealand in which few S. noctilio remain. The US is currently in experimental phases of introduction. The nematode may be raised in laboratory conditions and trees are inoculated with a gel medium in which they are suspended (Hurley, 2007; Haugen, 2005; Hocking, 1968; Bain, 2005; Bedding, 1974; SSPR, 2006).
Sirex noctilio larvae feed on a symbiotic fungus Amylostereum areolatum placed in host trees by ovipositing females. A phytotoxic fungus dries and kills tree cells allowing A. areolatum to spread. Larvae feed on this fungus throughout its normally one year developmental cycle. Adults do not feed but live off of stored fat, living only long enough to reproduce (Zondag, 1977).
Oviparous. Sexual, and facultative parthenogenetic. Mating of Sirex noctilio occurs in upper tree branches where males swarm on suitable days, which consists of temperatures of at least above 14° C, preferably above 30° C, sunny with intermediate to low humidity. This swarming behaviour by males is triggered by contact with other males and the presence of females. Individual females lay between 25-450 eggs. Mated females produce both male and female progeny, while unmated females yield only males. The typical ratio of males to females is approximately 10:1 (Morgan, 1968; Haugen, 2005). However sex ratio can vary greatly from almost 1:1 to well over 20:1 of males to females. It is possibly influenced by how established Sirex is in a particular area, but more work is needed to explain the major variation (B. Hurley, pers. comm.).
Eggs of Sirex noctilio are deposited in shafts drilled into the xylem of the host tree, along with a toxic mucus and arthrospores of the symbiotic fungus Amylostereum areolatum by female adults. Females excrete the mucus from glands and release arthrospores from their mycangium, pockets on either side of the fold between the first and second abdominal segments which carry the symbiotic fungal spores. They both travel down to the ovipositor where they are placed in the tree along with eggs. Female larva also possess these spores. Optimal eclosion (hatching) occurs after 10-12 days at about 25° C. Exposure to carbon dioxide, which is produced by the fungus, is shown to accelerated development and emergence from the egg. Larvae emerge and feed on the fungal mycelium by secreting saliva that dissolves nutrients so they may be ingested. They bore galleries throughout the tree leaving frass (waste) behind. S. noctilio typically goes through six or seven larval instars (phases), but they may have 5-12. The first instar moves about a centimeter up. In the second, they acquire mycelium nutrients and store it in hypopleural organs. By the end of the third, it will only have moved about 2cm. The fourth and fifth instars turn towards the heartwood at the center of the tree boring its way up a meandering path. It eventually turns toward the surface to pupate. The final gallery is usually about 12-15cm long. Natural development of most larvae takes 10-11 months, and mature larvae pupate close to the barks surface, emerging about 3 weeks later through holes about 3-7mm in diameter. About 25% of larvae don't emerge until the next season, taking two years to develop. Adults emerge sexually mature, males emerging first. Adults live a maximum of 12 days surviving on stored fat. Often, actively ovipositing females live only 3-4 days. (Madden, 1981; Haugen, 2005; Zondag, 1977, Borchert, 2006).
Reviewed by: Brett P. Hurley, Forestry and Agricultural Biotechnology Institute (FABI) University of Pretoria, South Africa
Principal sources: Hurley, B.P., Slippers, B., and Wingfield, M.J. 2007. A comparison of the control results for the alien invasive woodwasp, Sirex noctilio, in the southern hemisphere. Agricultural and Forest Entomology. Vol. 9: 159-171.
SSPR. 2006. SirexScience Panel Report. Indianapolis, IN.
Haugen, D.A. and Hoebeke, R.E. 2005. Pest Alert: Sirex woodwasp-Sirex noctilio F. (Hymenoptera; Siricidae). USDA Forest Service Northeastern Area State and Private Forestry, 11 Campus Boulevard, Suite 200, Newtown Square, PA 19073.
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Friday, 23 November 2007