Trypodendron domesticum

Name:   Trypodendron domesticum
Pest Authorities:  (Linneaus)
Taxonomic Position:  Insecta: Coleoptera: Scolytidae
Sub-specific Taxon:  
Pest Type:   Insect
Common Name(s):
   European hardwood ambrosia beetle (English)
   Buchennutholzborkenkäfer (German)
   Laubnutzholzborkenkäfer (German)
   Lauvvedborer (Norwegian)
   Le scolytide domestique (French)
   Dermestes domesticum Linneaus
   Apate limbata Fabricius
   Xyloterus domesticum Linneaus
Numerical Score:  6
Relative Risk Rating:  High Risk
Uncertainty:   Very Uncertain
Establishment Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism has successfully established in location(s) outside its native distribution
  • Suitable climatic conditions and suitable host material coincide with ports of entry or major destinations.
  • Organism has demonstrated ability to utilize new hosts
  • Organism has active, directed host searching capability or is vectored by an organism with directed, host searching capability.
  • Organism has high inoculum potential or high likelihood of reproducing after entry.
Justification: Established infestations of Trypodendron domesticum were discovered in British Columbia, Canada in 1997 and adults were collected in traps on Prince Edward Island, Canada in 1998 (Canadian Food Inspection Agency 1997, 1998). Suitable climatic conditions and hosts coincide with other North American ports of entry, especially those near broadleaf forests on the eastern portions of the continent. This insect has demonstrated ability to utilize new hosts: big leaf maple in western Canada and black locust, which has been introduced into Europe. It has an active, directed host searching capability and an established record of being able to reproduce after entry.

Spread Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism is capable of dispersing more than several km per year through its own movement or by abiotic factors (such as wind, water or vectors).
  • Organism has demonstrated the ability for redistribution through human-assisted transport.
  • Organism has a high reproductive potential
  • Potential hosts have contiguous distribution.
  • Newly established populations may go undetected for many years due to cryptic nature, concealed activity, slow development of damage symptoms, or misdiagnosis.
  • Eradication techniques are unknown, infeasible, or expected to be ineffective.
  • Organism has broad host range.
Justification: Trypodendron domesticum adults are capable of dispersing several km per year via independent flight and are also subject to wind dispersal. This insect has been intercepted at North American ports of entry on several occasions (Haack 2001, Phillippe et al. 1998). It has a high reproductive potential and a broad host range. Moreover, potential hosts have contiguous distributions in many parts of North America. Newly established populations could go undetected for long periods because of the cryptic nature of the immature stages. Also, the adults and damage superficially resembles indigenous ambrosia beetles. This would make eradication programs difficult to implement and of questionable effectiveness.

Economic Potential Is Moderate Risk
The relevant criteria chosen for this organism are:  
  • Organism attacks hosts or products with significant commercial value (such as for timber, pulp, or wood products.
  • Damage by organism causes a decrease in value of the host affected, for instance, by lowering its market price, increasing cost of production, maintenance, or mitigation, or reducing value of property where it is located.
  • Organism may cause loss of markets (domestic or foreign) due to presence and quarantine significant status.
Justification: This insect and resultant damage could have severe economic impacts on the hardwood lumber industry, especially high quality products such as veneer, paneling and furniture. Injury to living trees could create infection courts for decay fungi, resulting in decay or tree death. Plant quarantine programs designed to slow the spread of this insect could have additional impacts resulting from restrictions on movement of hardwood lumber or other products or additional treatments to wood prior to shipment.

Environmental Potential Is Low Risk
The relevant criteria chosen for this organism are:  
Justification: Ambrosia beetles are instrumental in the decomposition of dead wood. Provided that Trypodendron domesticum confines its attacks to dying and recently dead trees or freshly cut logs, no environmental impacts are envisioned as a result of establishment.

Trypodendron domesticum has a broad host range and infests many broadleaf trees.

In its natural range it has been reported from: oak, Quercus spp.; beech, Fagus sylvatica and Fagus sylvatica ssp. orientalis; maple, Acer spp.; alders, Alnus incana and Alnus glutinosa; hornbeams, Carpinus betulus and Carpinus orientalis; birch, Betula spp.; mountain ash, Sorbus aucuparia and Sorbus aria; linden, Tilia spp.; cherry, Prunus spp., Persian walnut, Juglans regia; white mulberry, Morus alba; black locust, Robinia pseudoacacia, which is exotic to Europe; ash, Fraxinus spp., Caragana spp., chestnut, Castanea sativa; thornapple, Crataegus spp.; holly, Ilex aquifolium; apple, Malus domestica; and willow, Salix caprea (Schwenke 1974, Grüne 1979, Bright and Skidmore 1997, Wood and Bright 1992).

In Canada, where is has recently been introduced and established, Trypodendron domesticum has been found breeding in a recently dead big leaf maple, Acer macrophyllum (Canadian Food Inspection Agency 1997).

     This insect is found in western Asia including Turkey (Schimitschek 1944). A report by Wood and Bright (1992) lists the “ western former USSR” as a region of this insect’s occurrence.
      Trypodendron domesticum is widely distributed in Europe west of the Ural Mountains (Russia). It has been reported from Austria, Belgium, Bulgaria, Czech Republic, Denmark, England, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Luxemburg, Netherlands, Norway, Poland, Romania, Sardinia, Scotland, Slovakia, Spain, Sweden, Switzerland, western Russia and the countries of the former Yugoslav Republics (Alexander 1997, Bright and Skidmore 2002, Vité 1952, Voolma 1996, Wood and Bright 1992).
North America:
     Established populations of this insect were recently discovered in Canada including Prince Edward Island and British Columbia (Canadian Food Inspection Agency 1997, 1998).
The genus Trypodendron consists of a number of species of ambrosia beetles indigenous to Asia, Europe and North America. Several species are considered of economic importance including T. lineatum, which has a holarctic distribution and is a major pest of freshly harvested logs in coastal British Columbia, Canada and adjoining areas of the U.S. (Furniss and Carolin 1977).

Host material for this insect is the sapwood of dying or stressed trees or trees that have died within the past two years and recently cut logs (Shore and McLean 1995). Host selection is based on biochemical factors not fully understood. The trees must have a high moisture content and be of an acceptable soundness and specified temperature range suitable to support both brood development and the fungus on which the larvae feed.

Trypodendron domesticum has one generation a year (Grüne 1979). Adults become active in early spring, usually March, when temperatures exceed 15ºC. (Schwenke 1974). Adult development is staggered so that adults are present from March to June (Vité 1952). When a suitable host, such as a freshly cut log, is found, females initiate attacks and secrete an aggregation pheromone that attracts other adults. They pair and copulate on the boles of host trees and each female subsequently bores a gallery into the bole or log. Only one entrance or exit hole exists, but a gallery with several branches (usually 2 to 5) is constructed up to ten cm. deep. An exception is oaks, where the galleries are shorter, 1-2 cm, resulting in less damage.

Spores of ambrosia fungi, which adhere to the adults, quickly germinate in the galleries and create a dark stain around their edges. These fungi are specific to Trypodendron domesticum. Two species of ambrosia fungi have been isolated from the galleries of T. domesticum in beech: Ceratocystis bacillospora Butin et Zimmermann and C. torulosa Butin et Zimmermann (Butin and Zimmermann 1972).

Female adults lay eggs in larval cradles, which are pod-like, gouged out crevices, and are oriented perpendicular to the gallery. After hatching, larvae feed on the ambrosia fungus and enlarge the cradle. They pupate in the cradles develop into adults. Excrement and sawdust are constantly removed by the males. The galleries are evacuated about July and the brood adults re-enter the galleries to overwinter. Overwintering may also take place in bark crevices (Vité 1952, Schimitschek 1973, Schwenke 1974, Eichhorn and Graf 1974).

Natural enemies include the parasitoids Perniphora robusta robusta and Ipideurytoma spessivtsevi Boucek & Novicky (Hymenoptera: Chalcidae). The rate of parasitism is generally low (< 10%), but when combined with a disease-causing organism, such as Pseudomonas septica Stutzer & Wsorow, the combined impact could be up to 50% mortality (Eichhorn and Graf 1974). Many of these natural enemies also occur on the closely related Trypodendron lineatum but are not known in North America (Krombein et al. 1979).

Economic Impact:    Damage caused by Trypodendron domesticum and its associated ambrosia fungi is boring damage and discoloration of wood. This reduces the quality of wood products, especially high quality hardwood veneer stock.

This insect usually confines its attacks to stressed, dying or recently dead trees. However, since late 1999, apparently vigorous beech forests in southern Belgium and neighboring portions of France, Luxembourg and Germany have been attacked by Trypodendron domesticum and T. sigantum. As of 2001, about 11% of the beech trees and 18% of the standing volume were attacked. The beetles apparently were attracted to cortical lesions, which developed as a result of a sudden and intense frost in November 1998 (Huart 2002).

Environmental Impact:   Ambrosia beetles are part of a complex of wood infesting insects instrumental in the decomposition of dead wood. They have no adverse environmental impacts.

Control:    Several techniques are available to reduce damage caused by ambrosia beetles. The most effective tactic is to remove harvested logs from the forest and process them as rapidly as possible (Vité 1956). Application of a water spray to decked logs in log yards during adult flight will help prevent attack (Shore and MacLean 1995).

Adult trapping with pheromones can reduce attacks in log yards. Ethanol or the pheromone 3 hydroxyl-3-methybutan-2-on is an effective bait and available from commercial sources (Kerck 1976, Grüne 1979). Lineatin, the pheromone blend for Trypodendron lineatum, will also attract T. domesticum (Shore and MacLean 1995). Chemical insecticides applied to boomed logs for ambrosia beetle control has been discontinued because of health risks (Shore 1992).

Kiln drying of infested material should kill brood and render it safe for shipping.

Symptoms:    Logs or tree boles infested by ambrosia beetles are usually peppered with pinholes about 2 mm in diameter. The entrance/exit holes are surrounded by a powdery, light yellow wood dust produced during gallery excavation. The wood is riddled with galleries and larval cradles and a dark stain is present along the galleries. These symptoms apply to all ambrosia beetles and are not specific to Trypodendron domesticum.

Morphology:    Adults are black or dark brown with yellow-orange stripes on the wing covers (elytra) and 3-4 mm long. The head and thorax are darker in color than the elytra. The pronotum is also black but may occasionally be reddish-yellow. The last antennal segment is broad and oval. The lateral surface of the body is comprised of golden, densely packed hairs. These hairs are denser on males than females.

Larvae are white, legless, c- shaped, with a small brownish head. Thoracic segments are pronounced and conspicuous (Novak et al. 1976).

The pupa is excarate, white in color and somewhat glossy in appearance.

Testing Methods for Identification:    Examination of adults by a specialist in the family Scolytidae is required for positive identification.

Adult Scolytidae are capable of dispersal flights up to an accumulated distance of 45 km due to combinations of independent flight and wind dispersal (Knight and Heikkenen 1980, Jactel and Gaillard 1991, Jactel 1991). Physiological and olfactory factors force beetles to disperse by flight. A bubble of gas in the abdomen of many Trypodendron spp. must be eliminated prior to adults settling on a host. Flight activity facilitates the elimination of the gas bubble ( Larvae, pupae and brood adults can be easily moved over long distance via international trade in wood products including unprocessed logs, green lumber, crating, pallets and dunnage. Transport of fuel wood is a potential source of short distance spread.

Trypodendron domesticum has been intercepted in Canada from hardwood crating imported from Germany (Phillippe et al. 1998). Both T. domesticum and T. signatum have been intercepted in wooden crating at U.S. ports of entry, carrying various products from Europe (Haack 2001).

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Erhard John Dobesberger
Name and Address of the First Author:
Erhard John Dobesberger
Science Division
Canadian Food Inspection Agency
3851 Fallowfield Road
Ottawa, Ontario
Canada K2H 8P9
CREATION DATE:        01/02/03
MODIFICATION DATE:        05/06/04