Ambrosia Beetle | Xylosandrus amputatus (Blandford)

California Pest Rating for
Ambrosia Beetle |  Xylosandrus amputatus (Blandford)
Coleoptera: Curculionidae
Pest Rating: A


Initiating Event:

The United States Department of Agriculture’s Plant Epidemiology and Risk Analysis Lab has proposed changing the status of the ambrosia beetle Xylosandrus amputatus from actionable to nonactionable1.  A pest rating proposal is required to determine the impacts that this proposed change might have on California and to assign a permanent pest rating.

History & Status:

Background:  Xylosandrus amputatus is a small fungus-feeding ambrosia beetle1.  Female beetles carry a symbiotic fungus and inoculate host trees1.  Adults and larvae then feed on the fungus1.  In its native range this beetle has been collected from trees in the families Anacardiaceae, Ebenaceae, Geraniaceae, Lauraceae, Moraceae, Rhamnaceae, Sapindaceae, Styracaceae, and Theaceae2.  Reported hosts include maple (Acer sp.)1, sumac (Rhus trichocarpa)1, Diospyros morrisiana1, zonal geranium (Pelargonium x hortorum)1, Actinodaphne lanciflora1 (possibly lancifolia), camphor tree (Cinnamomum camphora)1, Cinnamomum mairei1, Cinnamomum osmophloeum1, Machilus sp.1, Persea (Machilus) thubergii1, fig (Ficus carica)1, jujube (Ziziphus jujube)1, snowbell (Styrax suberifolium)1, and Stewartia monoderpha1 (possibly monodelpha).  The beetles can be rapidly transported long distances when infested wood products such as firewood are moved.

Worldwide Distribution:  Xylosandrus amputatus is native to Asia (China, Japan, Korea, and Taiwan)1,2.  The beetle is only known to have invaded Florida and Georgia1.

Official Control Xylosandrus amputatus is not known to be under official control in any other states or nations.

California Distribution:  Xylosandrus amputatus has never been found in the environment of California.

California Interceptions:  Xylosandrus amputatus has never been intercepted by CDFA or the County Agricultural Commissioners.

The risk Xylosandrus amputatus would pose to California is evaluated below.

Consequences of Introduction:   

1) Climate/Host Interaction:  Xylosandrus amputatus is likely able to establish throughout USDA Plant Hardiness zones 7 through 101. This is a climatic match for most of California.  Suitable host plants are grown throughout this region as well.  The beetle 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:  Xylosandrus amputatus is known to feed on at least 314 species of plants in 9 plant families.  It 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: In Florida, Xylosandrus amputatus has spread 200 miles in 7 years, demonstrating a high dispersal potential1.  The beetle could be spread through the movement of infested wood, including firewood.  Ambrosia beetles also have high reproductive potential.  Xylosandrus amputatus 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: In Florida and Georgia, where Xylosandrus amputatus has become established, it has not been found attacking healthy, stressed, or dying trees1.  It has only been found in traps.  Until more information about its biology in Florida or Georgia is known, it is appropriate to consider impacts that the beetles could have on all known hosts.  Fig and jujube are both known hosts that are grown commercially in California.  If Xylosandrus amputatus were to become established in the state the beetle could lower crop yields and increase crop production costs.  Female beetles also vector a fungal symbiont, Ambrosiella beaveri1.  However, it is not known if this fungus is pestiferous1Xylosandrus amputatus 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: If Xylosandrus amputatus were to establish in California it is not likely to lower biodiversity, disrupt natural communities, or change ecosystem processes.  The beetle is not expected to feed on any threatened or endangered species or disrupt critical habitats.  The species might trigger new treatment programs in fig and jujube orchards, however it is not likely to significantly impact cultural practices or home/urban gardens.  However, known host trees are common ornamental plants in California and may be susceptible to attack, especially if trees that are stressed due to drought.  Xylosandrus amputatus 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.

Score the pest for Environmental Impact. Score:

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 Xylosandrus amputatus:  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: Xylosandrus amputatus has never been found in the environment of 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)


Although Xylosandrus amputatus is well established throughout most of Florida and part of Georgia, however the beetles are only known from traps.  There is no information as to what host plants the beetles are feeding on in these states or if host trees are healthy or stressed.  There is a possibility that they are feeding on additional host tree species.

Conclusion and Rating Justification:

Xylosandrus amputatus has never been found in California.  If it were to enter the state, it is likely to have significant impacts on ornamental trees and fig and jujube production.  An “A”-rating is justified.


Note:  If links do not work please copy and paste URLs into your browser.

1PPQ. 2017. DEEP report for Xylosandrus amputatus (Blandford) (Coleoptera: Curculionidae). United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine (PPQ), Raleigh, North Carolina. 4 pp.  To request a copy of this report please contact USDA.

2 Cognato, Anthony I., Rachel O. Olson, and Robert J. Rabaglia. 2011. An Asian Ambrosia Beetle, Xylosandrus amputatus (Blandford) (Curculionidae: Scolytinae: Xyleborini), Discovered in Florida, U.S.A. The Coleopterists Bulletin 65(1): 43-45.

Responsible Party:

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

Comment Period:* CLOSED

1/11/2018 – 2/25/2018


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Pest Rating: A


Posted by ls