Tag Archives: Camphor shot borer

Camphor Shot Borer | Cnestus mutilatus (Blandford)

California Pest Rating for
Camphor shot borer | Cnestus mutilatus (Blandford)
Curculionidae: Coleoptera
Pest Rating: A


Initiating Event:

The United States Department of Agriculture (USDA) has proposed changing the status of Cnestus mutilatus from actionable to non-actionable.  A pest rating proposal is required to determine a permanent pest rating for this beetle.

History & Status:

Background Cnestus mutilatus is a wood-boring beetle that prefers to attack stems that are 2-5 cm in diameter, including more than 20 botanical families1.  Female beetles bore into trees and inoculate them with fungi1.  Adult beetles and larvae feed on these fungi, and reside within the stems.  A wide variety of trees are attacked.

Known hosts include Aceraceae: Japanese maple (Acer palmatum)1, red maple (Acer rubrum) 1, sugar maple (Acer saccharum) 1, maples (Acer spp.) 1, Acer sieboldianum1; Betulaceae: American hophornbeam (Ostrya virginiana) 1, Japanese hornbeam (Carpinus laxiflora) 1; Cornaceae: flowering dogwood (Cornus florida) 1, dogwood (Cornus spp.) 1; Fabaceae: Albizia spp. 1, Ormosia hosiei1; Fagaceae: beech (Fagus grandifolia) 1, chestnut (Castanea spp.) 1, Japanese beech (Fagus crenata) 1, Quercus shumardii1; Hamamelidaceae: sweetgum (Liquidambar styraciflua) 1; Juglandaceae: hickory (Carya spp.) 1, Platycarya spp. 1; Lauraceae: camphor laurel (Cinnamomum camphora) 1, spicebush (Benzoin [Lindera] spp.) 1, Lindera erythrocarpa1, Lindera triloba1, Parabenzoin [Lindera] praecox1, Machilus [Persea] thunbergii1; Magnoliaceae: yellow poplar (Liriodendron tulipifera) 1; Meliaceae: Melia azedarach1; big leaved mahogany (Swietenia macrophylla) 1; Oleaceae: Osmanthus fragrans1; Taxodiaceae: Japanese cedar (Cryptomeria japonica) 1; Pinaceae: loblolly pine (Pinus taeda) 1; Rosaceae: black cherry (Prunus serotina) 1, wild plum (Prunus americana) 1; Theaceae: Camellia spp. 1; Ulmaceae: elm (Ulmus alata) 1; Vitaceae: muscadine grape (Vitis rotundifolia) 1. It has also been reported on Anacardiaceae, Cupressaceae, Melastomataceae, Papilionaceae, and Styracaceae1.  The beetles can be transported long distances when infested nursery stock or firewood is moved.

Worldwide Distribution: Cnestus mutilatus is native to Asia, and has invaded the eastern United States and established a widespread distribution there1.

Official Control: Cnestus mutilatus is not known to be under official control in any other states or nations.

California Distribution Cnestus mutilatus has never been found in the environment of California.

California Interceptions Cnestus mutilatus has never been intercepted by CDFA or County Agricultural agents.

The risk Cnestus mutilatus (Camphor shot borer) would pose to California is evaluated below.

Consequences of Introduction:   

1) Climate/Host Interaction: The native distribution of Cnestus mutilatus corresponds with Plant Hardiness Zones 5 through 131, which matches most of the state of California. One model predicts that this beetle will not find the western United States as favorable as the east due to precipitation and temperature requirements1,2.  However, this same model also predicted that the beetles would not find suitable habitats in other eastern states where the beetle has since been found.  Other invasive wood boring beetles with similar native Asian distributions are thriving in California.  The accuracy of predictive models for wood-boring beetle distributions could likely be improved by including data on the environment inside trees, where the beetles spend the majority of their lives.  Host trees of the beetle are widely grown as ornamentals in California.  Cnestus mutilatus can be expected to establish a widespread distribution in California and receives a High (3) in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California.  Score:

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: Cnestus mutilatus is highly polyphagous and receives a High (3) in this category.

Evaluate the host range of the pest. Score:

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: Cnestus mutilatus both disperses and overwinters as mated females so a single individual can found a new population.  Female beetles can fly 2-3km and can rapidly be transported long distances when infested nursery stock or firewood is moved1Cnestus mutilatus receives a High (3) in this category.

Evaluate the natural and artificial dispersal potential of the pest. Score:

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: Cnestus mutilatus attacks nursery stock and a variety of insecticide treatments have been developed for this pest.  If this beetle were to establish in California, it is likely to affect yields of nurseries and increase production costs.  The beetles also vector symbiotic fungi from tree to tree.  Known hosts of the beetle include cherry, plum, and grapes (Prunus serotina, Prunus americana, and Vitis rotundifolia).  If the beetles are able to feed on grapevines and other stone fruit trees, it could have significant impacts on California’s $5.58 billion grape industry and $21 billion fruit and nut crop industries.  Cnestus mutilatus receives a High (3) in this category.

Evaluate the economic impact of the pest to California using the criteria below. Score:

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: Cnestus mutilatus is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes.  The species is not expected to directly affect threatened or endangered species or disrupt critical habitats.  The beetle is likely to trigger new chemical treatments by the nursery industry and by residents who find infested plants unsightly.  Many host trees of the beetle are planted as ornamentals in California and are likely to be significantly affected by this pest.  Cnestus mutilatus receives a High (3) in this category.

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

Environmental Impact: D, E

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 Cnestus mutilatus (Camphor shot borer):  High (15)

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: Cnestus mutilatus has never been found in California and receives a Not established (0) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

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:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: High (15)


In some cases, Cnestus mutilatus is attracted to gasoline mixed with ethanol3.  Female beetles can bore into plastic fuel storage containers, causing fuel to leak out3.  This could potentially increase the risk of fire in California3.

Conclusion and Rating Justification:

Cnestus mutilatus has not been found in California and is expected to have significant economic and environmental impacts if it were to establish in the state.  An “A” rating is justified.


1 PPQ. 2017. DEEP report for Cnestus mutilatus (Blandford) (Coleoptera: Curculionidae)—Camphor shot borer. United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine (PPQ), Raleigh, NC. 5 pp.  To request a copy of this report please contact USDA.

2 Olatinwo, R., D. Streett, and C. Carlton. 2014. Habitat suitability under changing climatic conditions for the exotic ambrosia beetle, Cnestus mutilatus (Curculionidae: Scolytinae: Xyleborini) in the southeastern United States. Annals of the Entomological Society of America 107(4):782-788.  https://www.srs.fs.usda.gov/pubs/ja/2014/ja_2014_olatinwo_004.pdf

3 Carlton, Chris and Victoria Bayless.  2011. A case of Cnestus mutilatus (Blandford) (Curculionidae: Scolytinae: Xyleborini) Females Damaging Plastic Fuel Storage Containers in Louisiana, U.S.A. The Coleopterists Bulletin 65(3): 290-291. http://www.lsuinsects.org/resources/docs/publications/Carlton&Bayless2011Cnestus.pdf

Responsible Party:

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

Comment Period:* CLOSED

1/11/2018 – 2/25/2018


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Pest Rating: A


Posted by ls