Trypodendron signatum (Fabricius)

California Pest Rating for 
Trypodendron signatum (Fabricius)
Coleoptera: Curculionidae: Scolytinae
Pest Rating: A



Initiating Event:

Trypodendron signatum is currently Q-rated.  A permanent pest rating proposal is required to support an official pest rating.

History & Status:

Background: Trypodendron signatum is an ambrosia beetle that ranges in length from 3.2 to 3.5 mm and has distinctive yellow and black longitudinal stripes on the elytra (Oranen, 2013).  Like other ambrosia beetles, the adults excavate tunnels in wood, and the larvae feed on fungus that grows in these tunnels.  This species has been reported to live in deciduous trees, including Alnus spp., Fagus sylvatica, and Quercus spp. (Cebeci and Ayberk, 2010; Henin et al., 2003).  This beetle primarily utilizes dead trees, but this can still have an economic impact, as cut timber is damaged through the tunneling of this beetle and the staining by the associated ambrosia fungus (Oranen, 2013).  There are also reports of T. signatum attacking living trees.  For example, ambrosia beetles, including T. signatum, were reported to be responsible for large-scale death of beech (Fagus sylvatica) trees in Belgium in the early 2000s (Henin et al., 2003).  Research suggests that these trees were probably injured prior to beetle attack, and that this prior injury may have been the result of freezing damage.  However, later attacks appear to have taken place on healthy trees for unknown reasons (Henin et al., 2003).

Worldwide Distribution: Trypodendron signatum is broadly distributed across the Palearctic Region, from western Europe to south-eastern China (Balachowsky, 1949; Cebeci and Ayberk, 2010; Galko et al., 2014; Henin et al., 2003; Knizek, 2011;  Oranen, 2013; Ostrauskas and Tamutis, 2012).

Official Control: Trypodendron signatum is not known to be under official control anywhere.

California Distribution:  Trypodendron signatum is not known to be present in California (Symbiota Collections of Arthropods Network).

California Interceptions: Trypodendron signatum has been intercepted on wood from Europe (PDR # 927924).

The risk Trypodendron signatum would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Trypodendron signatum is widely distributed across Europe, from cold, northern areas to the Mediterranean. This beetle is known to feed on Alnus and Quercus species, which are widely distributed across California.  Based on this information, this beetle is likely capable of becoming established over a broad area in California.  Therefore, it receives a High (3) in this category.

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Trypodendron signatum is known to feed on trees in three genera. Therefore, it receives a Medium (2) in this category.

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Trypodendron signatum can fly (Gaubicher et al., 2002). Another species, lineatum (Olivier) was found to be capable of moving (presumably by flying) two and a half miles, and T. signatum may have similar dispersal ability (Dyer, 1961).  In addition, it has been intercepted multiple times on wood entering the United States from Europe, which demonstrates that it is capable of human-aided dispersal (Haack and Rabaglia, 2013).  Therefore, it receives a Medium (2) in this category.

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

3) Economic Impact: Trypodendron signatum appears to primarily feed and develop in dead or dying trees (including cut wood).  Other Trypodendron species that have been introduced to western Canada and the western United States have caused damage to logs and lumber, and it is possible that signatum could have the same impacts in California (Livingston, 2004; McLean, 1985).  There have been reports of T. signatum attacking and killing living (potentially injured) trees.  Injury to trees that could lead to attack by beetles can result from climate extremes, for instance, drought, or warm weather followed by extreme cold (Henin et al., 2003).  The resulting beetle damage could result in lower yield and high production costs for forest products.  Trypodendron signatum is an ambrosia beetle, so by definition it carries fungus that becomes established in the beetle galleries and is used as a larval food source.  There is evidence that the beetle-fungus relationship in a new area (after introduction) can be unpredictable and could include the beetle and its fungal associate being introduced simultaneously, possibly with the fungus developing into a more aggressive form in its new range, as well as the introduced fungus being carried by a native beetle or an introduced beetle becoming associated with (and vectoring) a fungus already present in the new area.  Therefore, Trypodendron signatum receives a High (3) in this category.

Economic Impact:  A, B, E

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: As already stated, Trypodendron signatum has the potential to kill trees, especially if the trees are stressed or injured. Oaks (Quercus) are an important component of many California ecosystems and this genus is known to be fed upon by this beetle.  Some of these oak species are rare.  Therefore, T. signatum receives a High (3) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: A, B

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 3

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Trypodendron signatum: Medium (12)

Add up the total score and include it here.

–Low = 5-8 points

–Medium = 9-12 points

–High = 13-15 points

6) Post Entry Distribution and Survey Information: Trypodendron signatum is not known to occur in California.  It receives a Not established (0) in this category.

–Not established (0) Pest never detected in California, or known only from incursions.

–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

–Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (12)


There is some uncertainty regarding the possible economic and environmental impact of this species on California.  There are many examples that illustrate the unpredictability of bark and ambrosia beetles, and it is apparent that various factors including climate, tree species, and fungus species interact, and that significant economic and/or environmental damage could result.  Climate change could result in a higher frequency of extreme weather events, which could lead to tree stress and increased ambrosia beetle damage.

Conclusion and Rating Justification:

This beetle is one of many ambrosia beetles that are thought to feed mostly in dead or dying trees.  However, it seems that a cautious approach is best with possible forest pests, especially when there is evidence (as there is in this case) that living trees can be affected.  The behavior of this beetle may be very different in California than it is in Europe; it could be significantly worse.  The fungus symbiosis raises special concerns, because the beetle could bring with it possibly pathogenic fungi new to California, or it could interact in a new way with fungi already here.  For these reasons, an “A” rating is justified.


Balachowsky, A.  1949.  Faune de France: Tome 50.  Coléoptères Scolytides.  P. Lechevalier, Paris.

Cebeci, H.H. and H. Ayberk.  2010.  Ambrosia beetles, hosts and distribution in Turkey with a study on the species of Istanbul province.  African Journal of Agricultural Research.  5(10): 1055-1059.

Dyer, E.D.A.  1961.  Flight capability of ambrosia beetle (Trypodendron).  Canadian Department of Agriculture and Forestry Biological Division Bi-Monthly Progress Report.  17(1): 4.

Galko, J., Nikolov, C., Kimoto, T., Kunca, A., Gubka, A., Vakula, J., Zúbrik, M., and M. Ostrihoň.  2014.  Attraction of ambrosia beetles to ethanol baited traps in a Slovakian oak forest.  69(10): 1376-1383.

Gaubicher, B., De Proft, M., and J.C. Gregoire.  2002.  Trypodendron domesticum and Trypodendron signatum: Two scolytid species involved in beech decline in Belgium.  In (McManus, M.L. and A.M. Liebhold, eds): Proceedings; Ecology, survey and management of forest insects.  (pp. 134-135).  United States Department of Agriculture.

Haack, R.A. and R.J. Rabaglia.  2013.  Exotic bark and ambrosia beetles in the USA: Potential and current invaders.  In (J. Peña, ed.): Potential pests of agricultural crops (pp. 48-74).  CAB International.

Henin, J-M., Huart, O., and J. Rondeux.  2003.  Biogeographical observations on four scolytids (Coleoptera, Scolytidae) and one lymexylonid (Coleoptera, Lymexylonidae) in Wallonia (Southern Belgium).  Belgian Journal of Zoology.  133(2): 175-180.

Knizek, M. 2011. Subfamily Scolytinae Latreille, 1804. In (I. Loebl and A. Smetana, eds.): Catalogue of Palaearctic Coleoptera. Volume 7. Cucrulinoidea I. (pp. 204-251). Apollo Books.

Livingston, L.  2004.  Management guide for ambrosia beetle.  United States Department of Agriculture, United States Forest Service, Forest Health Protection and State Forestry Organizations.

McLean, J.A.  1985.  Ambrosia beetles: A multimillion dollar degrade problem of sawlogs in coastal British Columbia.  Forestry Chronicle.  61: 295-298.

Oranen, H.  2013.  The striped ambrosia beetle, Trypodendron lineatum (Olivier), and its fungal associates.  Thesis.  University of Helsinki.

Ostrauskas, H. and V. Tamutis.  2012.  Bark and longhorn beetles (Coleoptera: Curculionidae, Scolytinae et Cerambycidae) caught by multiple funnel traps at the temporary storages of timbers and wood in Lithuania.  18(2): 263-269.

Symbiota Collections of Arthropods Network.  Accessed February 6, 2018.


Kyle Beucke, 1220 N Street, Room 221, Sacramento, CA, 95814, 916-403-6741,[@]

Responsible Party:

Jason Leathers, 2800 Gateway Oaks, Sacramento CA 95833, (916) 654-1211,[@]

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4/20/18 – 6/4/18


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Pest Rating: A


Posted by ls