Tetropium fuscum
(brown spruce longhorn beetle)

Pictures

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Identity

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Preferred Scientific Name

• Tetropium fuscum (Fabricius, 1787)

Preferred Common Name

• brown spruce longhorn beetle

Other Scientific Names

• Callidium fuscum Fabricius, 1787

Local Common Names

• Finland: himmeä kuusijäärä
• Germany: Bock, Brauner Fichten-; Bockkäfer, Brauner Fichten-
• Norway: tofarg. granbarkbukk

EPPO code

• TETOFU (Tetropium fuscum)

Summary of Invasiveness

Top of page T. fuscum is believed to infest only dead and dying trees in its native range. However, populations were discovered in Nova Scotia, Canada (in 1990) infesting and reproducing in apparently healthy red spruce, Picea rubens (CFIA, 2003b). In the Nova Scotia infestation, hundreds of red spruce trees were infested, and many of these trees were dead at the time of investigation (Locke, 2001; CFIA, 2003b).

Taxonomic Tree

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• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Arthropoda
•             Subphylum: Uniramia
•                 Class: Insecta
•                     Order: Coleoptera
•                         Family: Cerambycidae
•                             Genus: Tetropium
•                                 Species: Tetropium fuscum

Description

Top of page Cherepanov (1988) published complete descriptions of the morphological features of the adults, larvae and pupae.

The adults are 8-17 mm long. The antennae are thin in T. fuscum, relative to congeners. They terminate beyond the middle of the male elytra, and over the first third of the female elytra (Bílý and Mehl, 1989). The terminal segment of the antennae is pointed in the females and rounded in the males (Cherepanov, 1988). The body of the adult is black, and the antennae, legs and elytra are reddish-brown with a whitish pubescence (Cherepanov, 1988; Bílý and Mehl, 1989). The basal part of the elytra is typically lighter in colour due to this pubescence (Cherepanov, 1988).

The oval eggs are 1 mm long and are white with a tinge of green (Locke, 2001; CFIA, 2003b). The larvae and pupae of Tetropium spp. are difficult to distinguish without technical expertise. The larvae of T. fuscum are whitish and a maximum of 28 mm long. The head capsule is reddish-brown and is a maximum of 3 mm in diameter (CFIA, 2003b). The whitish pupae are 17 mm long and 4 mm wide (Cherepanov, 1988; CFIA, 2003b).

Distribution

Top of page T. fuscum is native to Europe and northern Asia, where it is a secondary pest of coniferous trees. In 1999, it was determined that T. fuscum was established on apparently healthy trees in Nova Scotia, Canada. Scientists determined that the infestation had been present since at least 1990 but had been misidentified as Tetropium cinnamopterum (CFIA, 2003b). Other infestations of T. fuscum have since been discovered in Nova Scotia.

There are conflicting reports over the presence of T. fuscum in Siberia, Russia (Cherepanov, 1988; Bílý and Mehl, 1989).

Distribution Table

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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.

Risk of Introduction

Top of page T. fuscum has quarantine status in Canada, where it was reported to attack apparently healthy trees (CFIA, 2000).

Hosts/Species Affected

Top of page T. fuscum primarily infests Picea and Pinus (Bílý and Mehl, 1989), but Abies, Larix and hardwoods are also potential hosts (CFIA, 2003b). In North America, T. fuscum was reared from Picea rubens, Picea mariana, Picea glauca and Picea abies (Smith and Humble, 2000) and these trees were mainly over 10 cm in diameter at breast height (DBH) (Locke, 2001). In its native range, T. fuscum prefers mature stands (50 years old) of P. abies.

Host Plants and Other Plants Affected

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Growth Stages

Top of page Post-harvest, Vegetative growing stage

Symptoms

Top of page The larvae tunnel through the cambium and phloem of the tree, and eventually pupate in the xylem. This damage can girdle the tree, and lead to yellowing of the needles, and dieback of the crown and branches (Smith and Humble, 2000). The tunnels (a maximum of 6 mm in diameter) meander through the cambium and phloem, and are packed with frass and wood material (Smith and Humble, 2000). The mature larvae bore into the xylem of the tree to overwinter and pupate. This results in an L-shaped tunnel when a cross-section of the tree is taken (CFIA, 2003b). The infested trees tend to have a noticeable resin flow down the bark (Smith and Humble, 2000). Also, the adult exit holes (4 mm in diameter) are conspicuous in the bark of trees that have been infested for more than 1 year (Smith and Humble, 2000). Although the entire trunk of the tree is attacked by T. fuscum in North America, the populations in Europe and Asia appear to favour the lower parts of the trunk (Smith and Hurley, 2000). The galleries of Tetropium spp. are sometimes associated with wood-staining fungi in the genus Ophiostoma (Jacobs et al., 2003).

List of Symptoms/Signs

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Biology and Ecology

Top of page The biology of T. fuscum is similar to that of Tetropium castaneum (Bílý and Mehl, 1989). In the spring and early summer, the females lay eggs in the cracks and crevices of bark on susceptible trees (Smith and Humble, 2000; CFIA, 2003b). The eggs are typically laid singly but can occur in clusters of up to ten (CFIA, 2003b). In its native range, T. fuscum typically colonizes the lower parts of the trees, but in North American infestations, T. fuscum galleries were found up to 7 m high on the trunks of susceptible trees (Smith and Hurley, 2000).

After 10-14 days, the larvae hatch and begin to tunnel in the cambium and phloem of the tree (CFIA, 2003b). The larvae produce irregular galleries filled with frass in the living bark of the tree for about 2 months. They then tunnel perpendicular to the bark, 2-4 cm into the xylem, to pupate (CFIA, 2003b). Before pupation, the larvae turn 90º from their tunnel for 3-4 cm, resulting in an L-shaped tunnel when a cross-section of the tree is taken (CFIA, 2003b). The larvae overwinter 4 cm beneath the surface of the wood (CFIA, 2003b).

Pupation takes place in an oval pupal chamber in the xylem during the spring, around May (Bílý and Mehl, 1989; Smith and Humble, 2000; CFIA, 2003b). Wood-staining fungi, Ophiostoma spp. (most often Ophiostoma tetropii), are associated with infestations of Tetropium spp. in North America and throughout the world (Smith and Humble, 2000; Jacobs et al., 2003).

The adults eclose after 14 days, and survive for 3 weeks during June, July and August (Bílý and Mehl, 1989; CFIA, 2003a). The females emerge with a full complement of eggs (average of 80 eggs), and do not require a pre-oviposition period, as do many other cerambycids (Smith and Humble, 2000). Throughout much of its range, T. fuscum is univoltine (Bílý and Mehl, 1989).

Natural enemies

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Notes on Natural Enemies

Top of page There are a number of anecdotal reports of natural enemies that are associated with T. fuscum in North America, Europe and Asia. One species of asilid, Laphria gilva [Choerades gilva], feeds as a larva on T. fuscum and Tetropium castaneum larvae in their native ranges (Lavigne et al., 2000). A comprehensive survey of natural enemies that may act as biological control agents of T. fuscum is underway.

Means of Movement and Dispersal

Top of page Natural Dispersal (Non-Biotic)

Cerambycids are generally good fliers, but it is not known how far T. fuscum can disperse.

Movement in Trade

It is believed that T. fuscum has been introduced to the UK from continental Europe (Bílý and Mehl, 1989), and to Canada (Smith and Humble, 2000), from wood packing material or dunnage.

Plant Trade

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Plant parts not known to carry the pest in trade/transport
Bulbs/Tubers/Corms/Rhizomes
Flowers/Inflorescences/Cones/Calyx
Fruits (inc. pods)
Growing medium accompanying plants
Leaves
Roots
Seedlings/Micropropagated plants
True seeds (inc. grain)

Wood Packaging

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Impact

Top of page In Europe and Asia, T. fuscum attacks dead or dying trees except during outbreak periods. During population outbreaks, T. fuscum can attack living trees and reduce the quality of the timber (CFIA, 2003b). These outbreak populations can persist for 10 years (CFIA, 2003b). In North America, red spruce (Picea rubens) is an important tree for lumber, pulp and paper, and T. fuscum has been shown to infest apparently healthy stands of P. rubens. A serious insect pest of P. rubens could have significant economic implications for North American wood industries (Locke, 2001). In addition to causing feeding damage to trees, a wood-staining fungus, Ophiostoma tetropii was introduced into Nova Scotia, Canada, with T. fuscum. Although this species of fungus is not pathogenic, it may further depreciate the value of the infested timber (Jacobs et al., 2003).

Environmental Impact

Top of page The spruce tree is a major component of the North American boreal forests (Locke, 2001). Although T. fuscum is thought to typically only attack dead or dying trees in its native habitat, established populations in North America infested healthy Picea rubens. The environmental implications of the establishment of a wood-boring beetle that infests spruce could be severe to the North American boreal ecosystem.

Detection and Inspection

Top of page The infested trunks of living trees often have copious amounts of resin on the bark. The oval exit holes of the adults (4 mm in diameter) are visible externally in infested wood. When the bark is removed from the infested trees, the larval galleries (a maximum of 6 mm in diameter) are present. They meander through the cambium and phloem and are packed with frass and wood material. In the spring, a cross-section of the tree will reveal an L-shaped gallery that penetrates the xylem where the larvae pupate. Scientists in North America are actively pursuing lures and attractants that can be used to survey and trap T. fuscum (Sweeney et al., 2004, 2006; Silk et al., 2007).

Similarities to Other Species/Conditions

Top of page Worldwide there are 17 species in the genus Tetropium (Bílý and Mehl, 1989), seven of which are found in the Palearctic and six inhabit the Nearctic (Cherepanov, 1988). T. fuscum is superficially similar to several other Tetropium spp. and North American infestations were originally misidentified as Tetropium cinnamopterum (CFIA, 2003b). It is important to consider the worldwide constituency of the genus when identifying unknown Tetropium spp.. Tetropium castaneum is another potentially invasive member of the genus that is easily discernible from T. fuscum because of T. fuscum's bi-coloured elytra and thinner antennae (Cherpanov, 1988).

Prevention and Control

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The early detection of T. fuscum infestations is key to eradication efforts. The only treatment for T. fuscum in natural settings is to remove the infested material, and cutting- and chipping-infested wood. Heat treatment is an effective phytosanitary method to ensure that wood does not contain any live T. fuscum (Mushrow et al., 2004). The solid wood packing material should be heat-treated at 56ºC for at least 30 minutes (CFIA, 2003a).

References

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Bíl8 S; Mehl O, 1989. Longhorn Beetles (Coleoptera, Cerambycidae) of Fennoscandia and Denmark. Lieden, The Netherlands: E. J. Brill/Scandinavian Science Press Ltd. Fauna Entomologica Scandinavica, Vol. 22.

CFIA, 2000. Halifax park is under quarantine. News release by the Canadian Food Inspection Agency. Canadian Food Inspection Agency. http://www.inspection.gc.ca/english/corpaffr/newcom/2000/20000530e.shtml.

CFIA, 2003. Entry requirements for wood packaging produced in all areas other than the United States. Plant Health Division, Plant Products Directorate, Canadian Food Inspection Agency, Nepean, Ontario, Canada. Publication no. D-98-08. http://www.importers.ca/important_03/03_03_28woodpacking.doc.

CFIA, 2003. Tetropium fuscum (Fabricius) Brown spruce longhorn beetle. Canadian Food Inspection Agency Data Sheet. http://www.inspection.gc.ca/english/sci/surv/data/tetfuse.shtml.

Danilevsky ML, 2003. Systematic list of longicorn beetles (Cerambycoidea: Coleoptera) of Europe. http://marilyn.uochb.cas.cz/~natur/cerambyx/list_europe.htm.

Humble LM; Allen EA, 2006. .

IPPC, 2010. Update on the Brown Spruce Longhorn Beetle (BSLB), Tetropium fuscum (Fabricius), in Nova Scotia, Canada. IPPC Official Pest Report, CAN-05/1. Rome, Italy: FAO. https://www.ippc.int/index.php?id=1110520&no_cache=1&type=pestreport&L=0

IPPC, 2011. First detection of brown spruce longhorn beetle, Tetropium fuscum (Fabricius), in New Brunswick. IPPC Official Pest Report, No. CAN-15/1. Rome, Italy: FAO. https://www.ippc.int/

IPPC, 2013. Update on the Brown Spruce Longhorn Beetle, Tetropium fuscum (Fabricius), in Nova Scotia, Canada. IPPC Official Pest Report, No. CAN-27/1. Rome, Italy: FAO. https://www.ippc.int/

Jacobs K; Siefert KA; Harrison KJ; Kirisits K, 2003. Identity and phylogenetic relationships of ophiostomatoid fungi associated with invasive and native Tetropium species (Coleoptera: Cerambycidae) in Atlantic Canada. Canadian Journal of Botany, 81:316-329.

Lavigne R; Dennis S; Gowen JA, 2000. Asilid literature update, 1956-1976. Laramie, WY, USA: Cooperative Extension Service, University of Wyoming, SM-36.

Locke S, 2001. Brown spruce longhorn beetle Tetropium fuscum (Fabricius). http://www.dal.ca/~dp/webliteracy/projects/beetle/beetle3.html.

Mushrow L; Morrison A; Sweeney J; Quiring D, 2004. Heat as a phytosanitary treatment for the brown spruce longhorn beetle. Forestry Chronicle, 80(2):224-228.

NAPPO, 2013. Phytosanitary Alert System: Update on the brown spruce longhorn beetle, Tetropium fuscum (Fabricius), in Nova Scotia, Canada. Phytosanitary Alert System: Update on the brown spruce longhorn beetle, Tetropium fuscum (Fabricius), in Nova Scotia, Canada. NAPPO. http://www.pestalert.org/oprDetail.cfm?oprID=542

Silk PJ; Sweeney J; Wu JunPing; Price J; Gutowski JM; Kettela EG, 2007. Evidence for a male-produced pheromone in Tetropium fuscum (F.) and Tetropium cinnamopterum (Kirby) (Coleoptera: Cerambycidae). Naturwissenschaften, 94(8):697-701. http://www.springerlink.com/content/g40g231294w86772/fulltext.html

Smith GA; Humble LM, 2000. The brown spruce longhorn borer. Victoria, BC, Canada: Exotic Forest Pest Advisory, Natural Resources Canada, Canada Forest Service. http://www.atl.cfs.nrcan.gc.ca/index-e/what-e/science-e/entomology-e/bslb-e/exotic-pest.pdf.

Smith GA; Hurley JE, 2000. First North American record of the palearctic species Tetropium fuscum (Fabricius) (Coleoptera: Cerambycidae). The Coleopterist's Bulletin, 54:540.

Sweeney J; Groot Pde; MacDonald L; Smith S; Cocquempot C; Kenis M; Gutowski JM, 2004. Host volatile attractants and traps for detection of Tetropium fuscum (F.), Tetropium castaneum L., and other longhorned beetles (Coleoptera: Cerambycidae). Environmental Entomology, 33(4):844-854. http://www.esa.catchword.org

Sweeney J; Gutowski JM; Price J; Groot Pde, 2006. Effect of semiochemical release rate, killing agent, and trap design on detection of Tetropium fuscum (F.) and other longhorn beetles (Coleoptera: Cerambycidae). Environmental Entomology, 35(3):645-654. http://oberon.esa.catchword.org/vl=27545441/cl=13/nw=1/rpsv/cw/esa/0046225x/v35n3/s10/p645

Distribution Maps

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