Dwarf Siberian pine beetle | Dryocoetes pini

California Pest Rating  for
Dwarf Siberian Pine Beetle | Dryocoetes pini
Coleoptera: Curculionidae: Scolytinae
Pest Rating: A



Initiating Event:

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

History & Status:

Background: This bark beetle measures approximately 2.5 mm in length.  Adults tunnel through the phloem (inner bark), where eggs are laid.  The larvae feed on the phloem.  This species has been reported to feed on pine (Pinus spp.), larch (Larix spp.), fir (Abies spp.), and spruce (Picea spp.) (European and Mediterranean Plant Protection Organization; Niijima, 1909).  The beetle is apparently not known as a significant pest in its native range (European and Mediterranean Plant Protection Organization).  Dryocoetes species are usually considered “secondary pests” and only attack dead, injured, or otherwise compromised host trees (Vega & Hofstetter, 2014).  At least one species, Dryocoetes confusus Swaine, is a serious pest of fir trees; it is apparently the most destructive member of the genus in North America (CABI,  2017; Hansen, 1996; Vega & Hofstetter, 2014).  The pathogenic fungus Grosmannia dryocoetis is associated with D. confuses (Vega & Hofstetter, 2014).  Similar fungi may also be associated with other Dryocoetes species, including D. pini.

Worldwide Distribution: Dryocoetes pini occurs in the Russian Far East, China, South Korea, and Japan (European and Mediterranean Plant Protection Organization; Park, 2016; Shiraki, 1952).  The species is not known to be present in North America.

Official Control: This species is not known to be under official control anywhere.

California Distribution: This species does not appear to be present in California (Symbiota Collections of Arthropods Network).

California Interceptions: This species is not known to have been intercepted in California.

The risk Dryocoetes pini would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: This species appears to occur primarily in areas with a temperate climate. It is possible that it could thrive in a large portion of California if it was introduced.  The tree genera that this species is known to feed upon occur throughout California.  Therefore, Dryocoetes pini 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: As stated above, Dryocoetes pini has been reported from several coniferous genera. Therefore, pini 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: Dryocoetes pini is presumably capable of flight. Movement of wood (especially firewood) is a likely pathway for the human-aided dispersal of this species if it was to be introduced.  Reproductive potential is unknown for this species.  Therefore, pini 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.

4) Economic Impact: Dryocoetes pini has been reported to be associated with several genera of conifers, including Pinus.  There is a possibility that, if this species was to be introduced to California, it could have a different impact than what is observed in its native range, including killing trees, which could reduce yield of timber.  Significant infestations also have the potential to impact the recreational value of forests.  Therefore, it receives a Low (1) in this category.

Economic Impact:  A

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: 1

– 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: Major outbreaks of bark beetles have the potential to kill large numbers of trees, which can have long-lasting impacts. Such impacts could include changes in forest composition, destabilization of soil, and even fire dynamics (Jenkins et al., 2008).  There are rare or threatened conifers in California that could be impacted by the introduction of pini.  Therefore, it 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 Dryocoetes pini: Medium (11)

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: Dryocoetes pini 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 (11)


There is little information available on this species, so it was necessary to draw upon information regarding other species in the genus as well as other bark beetle genera.  There are also no examples of introductions involving this species, so assessment of the impacts of this species requires speculation.

Conclusion and Rating Justification:

Bark beetles can have significant impacts on forests.  One native species in the genus Dryocoetes, D. confusus, is an important pest in western forests.  Even though there is little information on the biology of D. pini, it seems justifiable to use caution and assign it an “A” rating.


CABI.  2017.  Invasive Species Compendium. Wallingford, UK: CAB International. www.cabi.org/isc

European and Mediterranean Plant Protection Organization.  Forest pests on the territories of the former USSR.


Hansen, E.M.  1996.  Western balsam bark beetle, Dryocoetes confusus Swaine, flight periodicity in northern Utah.  Great Basin Naturalist.  56(4): 348-359.

Jenkins, M.J., Hebertson, E., Page, W., & Jorgensen, C.A.  2008.  Bark beetles, fuels, fires and implications for forest management in the Intermountain West.  Forest Ecology and Management.  254: 16-34.

Niijima, Y.  1909.  Die Scolytiden Hokkaidos unter Berücksichtigung ihrer Bedeutung für Forstschäden.  The Journal of the College of Agriculture, Tohoku Imperial University.  3: 109-179.

Park, S.  2016.  Taxonomic review of Scolytinae and Platypodinae (Coleoptera: Curculionidae) in Korea.  Ph.D. thesis.  Seoul National University.

Shiraki, T.  1952.  Catalogue of injurious insects in Japan.  Preliminary Study Number 71.  General Headquarters, Supreme Commander for the Allied Forces, Economic and Scientific Section, Natural Resources Division.  133 pp.

Symbiota Collections of Arthropods Network.  Accessed March 2, 2018. http://scan1.acis.ufl.edu

Vega, F.E. & Hofstetter, R.W.  2014.  Bark beetles: Biology and ecology of native and invasive species.  Academic Press.  640 pp.


Kyle Beucke, 1220 N Street, Room 221, Sacramento, CA, 95814, 916-403-6741, plant.health[@]cdfa.ca.gov

Responsible Party:

Jason Leathers, 2800 Gateway Oaks, Sacramento CA 95833, (916) 654-1211, plant.health[@]cdfa.ca.gov

Comment Period:* CLOSED

4/9/18 – 5/24/18


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Pest Rating: A


Posted by ls