small spruce bark beetle | Pest Rating Proposals and Final Ratings

California Pest Rating for

Small Spruce Bark Beetle | Polygraphus poligraphus (L.)

Coleoptera

Pest Rating: A

PEST RATING PROFILE

Initiating Event:

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

History & Status:

Background: Polygraphus poligraphus has been reported to feed on Norway spruce (Picea abies) and Scotch pine (Pinus sylvestris). Apparently, it prefers weakened trees but can attack healthy ones as well. Healthier trees may be attacked when population levels of the beetle are high, probably because tree defenses can be overwhelmed through mass attack. Polygraphus poligraphus, like many or most bark beetles, is associated with multiple species of fungi, and some of these may be pathogenic to trees.

Worldwide Distribution: Polygraphus poligraphus is native to Europe and has a wide distribution there, being found from Scandinavia to the Mediterranean and Eastern Europe.

Official Control: Although this species is considered a pest, it does not appear to be under official control in any country.

California Distribution: This species is not known to be present in California.

California Interceptions: Polygraphus poligraphus has apparently been intercepted one time in California, on wood from Belgium or Germany (PDR # 798650).

The risk Polygraphus poligraphus would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Although Polygraphus poligraphus has a wide distribution in Europe, extending from northern Europe to the Mediterranean, it appears that climates represented by much of its distribution may be colder than what is present in most of California. However, spruce and pine trees occur throughout California and are potential host trees of this beetle. Therefore, Polygraphus poligraphus receives a Medium (2) 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: Polygraphus poligraphus is known to attack at least two genera of coniferous trees. 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: Polygraphus poligraphus is capable of sustained flight. The species can also be artificially dispersed via movement of wood (including wood packing), as shown in one study where poligraphus emerged in a Canadian quarantine facility from wood packing from Norway. 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.

4) Economic Impact: There are challenges to predict the possible economic impact of Polygraphus poligraphus. The literature suggests that living trees are attacked by this species, and multiple species of fungi (some of them apparently pathogenic) can be vectored by it. If established, poligraphus could reduce the quality and/or yield of timber, which could result in the loss of markets for California timber. Therefore, it receives a High (3) in this category.

Economic Impact: A, B, C

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 stated above, there is evidence that Polygraphus poligraphus attacks living trees and could vector harmful fungi. This could have a significant impact on California forest ecosystems. There are several rare pines in California that could be impacted by the establishment of this beetle. 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 Polygraphus poligraphus: 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: Polygraphus poligraphus is not known to be present 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)

Uncertainty:

Polygraphus poligraphus is a bark beetle that primarily feeds on trees that are damaged or weakened, but some sources suggest that it can attack healthy trees. Hence, the impact of this species on natural and managed forests in California is difficult to predict. There is a possibility that the ability of P. poligraphus to overcome the defenses of healthy trees and the impact of its vectored fungi (as well as any interactions between this beetle and fungi already present in California) in California could be different from what is seen in Europe.

Conclusion and Rating Justification:

As mentioned above, there are uncertainties regarding the possible impact of this species. However, the fact that it does not yet occur in California, the evidence that it can (at least in some situations) attack living trees, and the fact that it can vector fungi suggest that an “A” rating is justified.

References:

Allen, E.A. and L.M. Humble. 2002. Nonindigenous species introductions: A threat to Canada’s forests and forest economy. Canadian Journal of Plant Pathology. 24: 103-110.

Alonso-Zarazaga, M.A., Kníñek, M., and S. Vit. 2017. Polygraphus poligraphus (Linnaeus). Fauna Europaea version 2017.06 https://fauna-eu.org

Kärvemo, S., Björkman, C., Johansson, T., Weslien, J., and J. Hjälten. 2017. Forest restoration as a double-edged sword: the conflict between biodiversity conservation and pest control. Journal of Applied Ecology. 1-11.

Krokene, P. and H. Solheim. 1996. Fungal associates of five bark beetle species colonizing Norway spruce. Canadian Journal of Forest Research. 26: 2115-2122.

Vojtěch, O., Křenová, Z., and J. Rastislav. 2013. Species of bark beetles (Scolytinae) collected in the Bohemian Forest at Smrčina/Hochficht two years after the Kyrill hurricane. Silva Gabreta. 19(3): 149-164.

Author:

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 Drive, Sacramento CA 95833, (916) 654-1211; plant.health[@]cdfa.ca.gov.

Comment Period:* CLOSED

1/16/2018 – 3/2/2018

*NOTE:

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