Tremex fuscicornis (Tremex wasp)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Natural enemies
- Notes on Natural Enemies
- Plant Trade
- Wood Packaging
- Environmental Impact
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Tremex fuscicornis (Fabricius, 1787)
Preferred Common Name
- Tremex wasp
Other Scientific Names
- Sirex camelogigas Christ
- Sirex fuscicornis Fabricius
- Sirex struthiocamelus Villers
- Tremex juxicernis Walker
- Tremex simulacrum Takeuchi
- Urocerus fuscicornis Latreille
- Xyloecematium fuscicornis Heyden
- Xyloterus fuscicornis Boie
International Common Names
- Spanish: avispa taladradora de la madera
Local Common Names
- Finland: ampiaspuupistiäinen
- TREXFU (Tremex fuscicornis)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Arthropoda
- Subphylum: Uniramia
- Class: Insecta
- Order: Hymenoptera
- Family: Siricidae
- Genus: Tremex
- Species: Tremex fuscicornis
Notes on Taxonomy and NomenclatureTop of page Fabricius originally described this wood wasp as Sirex fuscicornis in 1787 and it has undergone a number of changes in nomenclature since its original description.
DescriptionTop of page Eggs
Siricidae wasp eggs are cylindrical, creamy-white and approximately 1 mm long.
The mature larvae are on average 3 cm long. However, some individuals can reach 4 cm. They are creamy-white, with short antennae, distinct mandibles and three pairs of rudimentary legs that are approximately 0.5 mm long. The last abdominal segment has a distinct, dark spine.
The pupae are on average 3 cm long and white when they first form. They become darker prior to adult development. The pupae have distinct antennae and fully developed legs.
The adult males are completely black, including the antennae and legs. The wings are amber and much darker than the wings of the female. The females are larger than the males with a dark head and thorax. The abdomen has bands of alternating black and amber, with a long ovipositor on the last abdominal segment (Baldini, 2002; CSIRO, 2002).
DistributionTop of page T. fuscicornis is widely distributed across the broadleaf forests of Eurasia (Smith, 1978). This insect has become established in Australia and Chile (Baldini, 2002; CSIRO, 2002).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.Last updated: 23 Apr 2020
Risk of IntroductionTop of page Adult Siricidae are strong fliers and capable of flying several kilometres in search of suitable hosts. The immature stages are easily transported in wood products via international trade. The Chilean introduction of T. fuscicornis is believed to have originated from wooden crates infested with larvae and pupae, probably originating from China (Baldini, 2002). Further localized, human-assisted dispersal of this insect could be via infested fuel-wood, tree trimmings and other wood products.
A major concern in South America is that because Fagus spp. (beeches) are hosts within this insect's natural range, southern beeches, Nothofagus spp. are potential hosts. Several species of Nothofagus are important economic and ecological components of approximately 12 million ha of natural forests in central and southern Chile (Baldini, 2002). A similar situation exists in the Andean region of central and southern Argentina.
HabitatTop of page Within its native geographic distribution, T. fuscicornis confines its attacks to stressed or recently killed trees. In places where it has been introduced and becomes established, it can attack vigorous trees.
Hosts/Species AffectedTop of page T. fuscicornis attacks various species of broadleaf trees. Within its geographic range, it is recorded from a number of hosts including Fagus spp., Populus spp., Ulmus spp., Alnus spp., Quercus spp., Acer spp. and Prunus spp. (Smith, 1978). It has not been recorded on Pinus sp. or other conifers.
T. fuscicornis was introduced in Australia after 1996 and its hosts include poplars, Populus spp. and willows, Salix spp. In Chile, where it has recently become established, T. fuscicornis attacks Populus alba (white poplar), Populus deltoides (eastern cottonwood), Populus nigra (black poplar), Salix babylonica (weeping willow), Salix humboldtiana (Humboldt willow), Acer negundo (box-elder) and Robinia pseudoacacia (black locust) (Baldini, 2002).
Host Plants and Other Plants AffectedTop of page
Growth StagesTop of page Vegetative growing stage
SymptomsTop of page The symptoms of attack by T. fuscicornis in dead and dying trees are limited to the presence of round adult emergence holes, approximately 5 to 6 mm in diameter, in trees where this insect has completed its life cycle. Attacked trees develop thin or chlorotic foliage and ultimately die.
List of Symptoms/SignsTop of page
|Leaves / wilting|
|Leaves / yellowed or dead|
|Stems / internal feeding|
|Stems / visible frass|
|Whole plant / plant dead; dieback|
Biology and EcologyTop of page Life History and Habits
T. fuscicornis is a wood wasp in the family Siricidae. Wood wasp larvae bore into the wood of trees and live in a symbiotic relationship with wood-decaying fungi, which partially break down the cellulose before the larvae can use it for food. The genus Tremex contains several species of wood wasps that are indigenous to Eurasia and North America, and infest broadleaf trees. The pigeon tremex, Tremex columba, is found in North America, where it is widely distributed in Canada and the USA. It infests dead or weakened broadleaf trees. This insect is considered to be the most abundant member of the Siricidae in North America (Drooz, 1985; Smith and Schiff, 2002).
Relatively little is known about the life history and habits of T. fuscicornis in its native habitat. A report from Finland suggests that the symbiotic fungus associated with this insect may be Bjerkandera fumosa (Savela, 1998).
Some biological data are available from Chile where it has recently become established (Baldini, 2002). The females use their long ovipositor to deposit eggs in the cambium layer of host trees. The female simultaneously inoculates a phytotoxic mucus and a fungus, believed to be a species of Cerrena, into a tree. When the first-instar larvae emerge, they exclusively feed on the hyphae of the developing fungus. Later the larvae construct longitudinal, semi-circular galleries, which can run either upwards or downwards. The total length of a gallery is approximately 1 metre and it gradually increases in diameter as the larvae grow. Pupation occurs inside the wood at a depth of approximately 4 cm from the bark surface. Adult emergence occurs over an extended period from summer to autumn (October to May). Due to the prolonged period of adult emergence, it is possible to encounter all life stages during much of the growing season. The number of generations per year in Chile has not yet been established.
By comparison, the North American species, Tremex columba, which also infests broadleaf species, is believed to have one generation per year over most of its range. However, in New Brunswick, Canada, it has a minimum life cycle duration of 2 years. The fungus associated with T. columba is Daedalea unicolor [Cerrena unicolor] (Drooz, 1977; Smith and Schiff, 2002).
Natural enemiesTop of page
Notes on Natural EnemiesTop of page Little is known about the natural enemies affecting T. fuscicornis, probably because it is relatively uncommon throughout most of its natural range.
Ibalia drewseni, Ibalia leucospoides and Ibalia jakowlewi have been reported to attack the larvae of T. fuscicornis (Kierych, 1973; Pfeffer, 1983).
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Stems (above ground)/Shoots/Trunks/Branches||adults; eggs; larvae; nymphs; pupae||Yes||Pest or symptoms usually visible to the naked eye|
|Wood||adults; eggs; larvae; nymphs; pupae||Yes||Pest or symptoms usually visible to the naked eye|
|Plant parts not known to carry the pest in trade/transport|
|Fruits (inc. pods)|
|Growing medium accompanying plants|
|True seeds (inc. grain)|
Wood PackagingTop of page
|Wood Packaging liable to carry the pest in trade/transport||Timber type||Used as packing|
|Solid wood packing material with bark||Broadleaf species: lumber, crating, pallets, dunnage||Yes|
|Solid wood packing material without bark||Broadleaf species: lumber, crating, pallets, dunnage||Yes|
|Wood Packaging not known to carry the pest in trade/transport|
|Loose wood packing material|
|Processed or treated wood|
ImpactTop of page In their native habitats, the larvae of wood wasps bore into weakened and dying trees. They are usually considered to be of minor importance except for decreasing the value of lumber (Smith and Schiff, 2002). In its natural range, populations of T. fuscicornis are typically small and difficult to observe (Baldini, 2002). However, a report from the Ukraine indicated that outbreaks of this insect have occurred in birch and other broadleaf species (Kolomets, 1998).
In Chile, weakened, damaged or recently-cut trees are preferred. However, apparently vigorous trees of some hosts, such as Acer negundo, may also suffer attack. On vigorous trees, the first attacks occur on the branches. These cause dieback and weakening of the trees. The brood adults that emerge from the branches subsequently infest the main bole. All trees that are attacked are killed (Baldini, 2002). To date, extensive damage has occurred to windbreak and shelter-belt plantings (Baldini, 2002). The attacks are typically so heavy that a single poplar can produce 2000 individual brood adults (Baldini, 2002). Therefore, the wood is impossible to use for lumber or other wood products. Moreover, the rate of decay of infested wood is accelerated because of the action of the symbiotic fungi associated with T. fuscicornis (Baldini, 2002). Another significant impact has been the loss of poplar windbreak plantings around agricultural crops and fruit orchards. This exposes the orchards to high winds and results in reduced crop yields (Baldini, 2002).
Environmental ImpactTop of page T. fuscicornis is relatively uncommon within its geographic range and the ecological impact is negligible. In conjunction with its symbiotic fungus, it is probably a minor factor in the decomposition of dead trees. In Chile, up until now, attacks have been primarily confined to plantations of exotic species, and plantings in parks and gardens have been affected (Baldini, 2002). If this insect becomes established in natural forests and adapts to Nothofagus spp., which are important components of forests in southern Argentina and Chile, major ecological disruptions and loss of biodiversity could occur.
Detection and InspectionTop of page Wooden crating, pallets and dunnage should be inspected for larval galleries and insect life stages. The presence of round exit holes in logs or wood is used as an indication that wood wasps of the family Siricidae may have emerged from this material.
Similarities to Other Species/ConditionsTop of page The adult wood wasps of the genus Tremex can be separated from other Siricidae by the presence of relatively shorter antennae with only 14 to 15 segments. The head lacks a genal carina behind the eyes, the female ovipositor is shorter than the forewing and the hind wing has an anal cell. The adults also lack long golden hairs that usually characterize members of the siricid genus, Eriotremex (Smith and Schiff, 2002). Most Tremex spp. are similar in appearance and difficult to identify to species level. A taxonomist, with expertise in the Siricidae, should carry out a species identification.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.At present, direct control methods are not available for this insect. The following measures are suggested in cases where the introduction and establishment of T. fuscicornis results in the death of healthy trees. These are based on pest management measures currently in place for Sirex noctilio, in areas where this insect has been introduced in Southern Hemisphere pine plantations.
Forests, shelter-belts and ornamentals can be kept in a vigorous condition through regular scheduled thinning and proper watering. Other cultural measures include the rapid removal of freshly-cut logs of broadleaf species from forested areas during timber harvesting operations. The storage of logs under water sprays, debarking or rapid processing should be used to prevent wood wasp attacks in sawmills.
Chemical control measures have not been developed for wood wasps of the family Siricidae.
The fumigation and exposure of lumber and other wood products to high temperatures would kill all life stages of this insect.
If T. fuscicornis is introduced and established in conifer forests outside its geographic range and causes losses, the introduction of insect parasitoids in a classical biological control programme would be a potentially viable tactic.
Siricids tend to respond to host attractants and are not known to produce attractant pheromones. Consequently, pheromonal control is not a viable pest management tactic.
A trap-tree technique, used to monitor for the presence of Sirex noctilio, should also be effective for T. fuscicornis. This involves the injection of an herbicide into suppressed trees, which stresses them and makes them attractive to attack.
Integrated Pest Management
In Chile, an integrated approach that uses a combination of cutting and destroying infested trees plus the introduction of natural enemies, is under development. Low-level populations can be detected by establishing trap-trees, which are injected with a weak herbicide to make them attractive to adult T. fuscicornis. The parasitoid, Ibalia leucospoides is being evaluated as a potential biological control agent. The use of a parasitic nematode, which is an effective control for the wood wasp, Sirex noctilio, is also being considered (Baldini, 2002).
ReferencesTop of page
Baldini U-A, 2002. Tremex fuscicornis: Un factor de daño para el recurso forestal y agrícola. Agronomia y Forestal, 16:11-13.
CSIRO, 2002. 1. Common names: Tremex fuscicornis (Fabricius). CSIRO Australia and AFFA, Australia. http://www.ento.csiro.au/aicn/name_c/a_3632.htm.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Heidemaa M; Voolma K; Suda I, 1998. Species composition and distribution of the horntails (Hymenoptera, Siricoidea) of Estonia. Metsanduslikud Uurimused, 29:124-131.
Midtgaard F; Stokland JN; Sverdrup-Thygeson A, 1994. Tremex fuscicornis (Fabricius) (Hymenoptera, Siricidae) a new woodwasp for the Norwegian fauna. Fauna Norvegica Ser B, 41:97.
Savela; M, 1998. Lepidoptera and some other life forms. Bjerkandera fumosa. FUNET, Finland. http://www.funet.fi/pub/sci/bio/life/fungi/gasteromycetes/polyporales/bjerkanderaceae/bjerkandera/index.html#fumosa.
Smith DR, 1978. Pars 14, Suborder Symphyta. In: an der Vecht J, Shenefelt RD, eds. Hymenopterorum Catalogus (Nova edition). The Hague, Netherlands: Dr W Junk, BV.
Smith DR; Schiff NM, 2002. A review of the siricid woodwasps and their ibaliid parasitoids (Hymenoptera: Siricidae, Ibaliidae) in the Eastern United States, with emphasis on the mid-Atlantic region. Proceedings of the Entomological Society of Washington, 104(1):174-194; many ref.
Baldini UA, 2002. (Tremex fuscicornis: Un factor de daño para el recurso forestal y agrícola). In: Agronomia y Forestal, 16 11-13.
CABI, Undated. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI
CSIRO, 2002. Common names: Tremex fuscicornis (Fabricius)., Australia: CSIRO Australia and AFFA. http://www.ento.csiro.au/aicn/name_c/a_3632.htm
Heidemaa M, Voolma K, Süda I, 1998. Species composition and distribution of the horntails (Hymenoptera, Siricoidea) of Estonia. (Puiduvaablaste (Hymenoptera, Siricoidea) liigiline koosseis ja levik Eestis.). Metsanduslikud Uurimused. 124-131.
Midtgaard F, Stokland JN, Sverdrup-Thygeson A, 1994. Tremex fuscicornis (Fabricius) (Hymenoptera, Siricidae) a new woodwasp for the Norwegian fauna. In: Fauna Norvegica Ser B, 41 97.
Smith DR, 1978. Pars 14, Suborder Symphyta. In: Hymenopterorum Catalogus, [ed. by an der Vecht J, Shenefelt RD]. The Hague, Netherlands: Dr W Junk, BV.
Distribution MapsTop of page
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