Twobanded Japanese Weevil | Pseudocneorhinus bifasciatus

Twobanded Japanese Weevil
Figure 1: Pseudcneorhinus bifasciatus (Photo: Judy Gallagher)
California Pest Rating for
Name: Pseudocneorhinus bifasciatus Roelofs (twobanded Japanese weevil)
Synonym: Callirhopalus bifasciatus (Roelofs)
Order: Coleoptera
Family: Curculionidae
Pest Rating: A


Initiating Event:

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

History & Status:

Background:  Pseudocneorhinus bifasciatus is a stout, convex, and pear-shaped weevil with a short, blunt snout, and elytra much broader than its pronotum. It is approximately 5 mm long, and is covered with brown and grey scales that form two bands across the elytra (Thomas, 2005). The elytra are fused, and the hind wings are absent, so this weevil cannot fly. The adult weevils feed during the day on leaves.  They are easy to overlook due to their subdued brown coloration (Smith,1955).  They can cause significant damage to plants when they are abundant. This weevil is highly polyphagous and is known to feed on over 100 species of plants.  Recorded hosts include multiflora rose (Rosa multiflora), rose, azalea (Rhododendron spp.), privet (Ligustrum spp.), azalea, forsythia, geranium, hemlock, mountain laurel, lilac, strawberry, flowering dogwood, and perennial phlox.  In the northeastern United States, Pseudocneorhinus bifasciatus has one generation per year with egg laying taking place from the middle of May through October (Gyeltshen and Hodges, 2016).  Eggs are laid on fallen leaves within leaf-folds, and the edges of the leaf is then sealed by the weevil to form a “pod” (Zepp, 1978).  An egg “pod” contains one to nine eggs (Zepp, 1978).  The eggs hatch in 14 to 18 days (Allen, 1959).  The newly hatched larvae leave the “pod” and burrow into the soil. The larvae live in the soil and feed on the roots of host plants, but the extent of damage from their feeding is not well documented.  Allen (1959) found as many as 150 larvae per square foot, at depths ranging from one to nine inches, underneath infested privet hedges in New Jersey.  Larvae were found at depths ranging from one to nine inches (Allen, 1959).  These larvae started to pupate by early May, and adults emerged in late June and early July (Allen, 1959).  Although the weevil has a wide range of hosts, the Rosaceae family may be particularly vulnerable to this pest.  For example, one study showed that this weevil had the greatest reproductive success when adults were fed on foliage of Rosa multiflora Thunb. (Rosaceae) compared with four other species of other ornamental plants in three other families (Maier, 1983).  Another study found larvae of this weevil to cause damage to the roots of peach trees in Georgia (peaches are in the family Rosaceae; Cottrell and Horton, 2013).

Worldwide Distribution:  Pseudocneorhinus bifasciatus is native to China, Japan, Korea, Mongolia, and eastern Siberia.  It has been established on the east coast of the United States for more than 100 years and it is currently known to occur there from New England south to northern Florida and west to Illinois and Indiana (Thomas, 2005).  It has also been found in Oklahoma, although the distribution of the weevil in that state is unknown (Rebek and Grantham, 2008).

Official Control: Pseudocneorhinus bifasciatus is not known to be under official control.

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

California Interceptions:  Pseudocneorhinus bifasciatus was intercepted in a West Sacramento postal facility in an out-of-state shipment of crabapple in August 2015 (CDFA, 2015).

The risk Pseudocneorhinus bifasciatus would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: The weevil’s distribution extends from New England to Florida, indicating a wide temperature tolerance. It is not known if there are other climate limitations. This weevil is highly polyphagous, and it is presumed that suitable host plants are present throughout much of 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: Pseudocneorhinus bifasciatus, has been reported to feed on more than 100 species of plants in more than 25 families. It is primarily known for damaging ornamental plants, but it has been found to also damage vegetable and field crops (Day, 2014; Thomas, 2005). Therefore, it receives a High (3) 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: Pseudocneorhinus bifasciatus reproduces parthogenetically (Takenouchi et al, 1983).  This high reproductive capacity is offset by a limited dispersal potential.  The weevil’s wing covers are fused rendering it incapable of flight.  It could be dispersed through the movement of infected nursery stock (Wheeler and Boyd, 2005).  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: As described previously, Pseudocneorhinus bifasciatus has a very wide range of hosts including field and vegetable crops (Thomas, 2005; Day, 2014).  The weevil has the potential of lowering the value of nursery crops and the yield of agricultural crops.  Therefore, it receives a Medium (2) in this category.

Economic Impact:  A, B

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: 2

– 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 Pseudocneorhinus bifasciatus became established in California, it could attack a wide variety of ornamental and garden plants. The impact of the infestation could trigger treatment programs.  This pest may also pose a threat to endangered species such as Rosa minutifolia and Potentilla hickmannii.  Therefore, this beetle receives a High (3) in this category.

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

Environmental Impact: B, 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 Pseudocneorhinus bifasciatus: High (13)

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: Pseudocneorhinus bifasciatus 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: High (13)


There is significant uncertainty regarding the suitability of the California climate and the ability of Pseudocneorhinus bifasciatus to become established in California. It apparently can tolerate a wide range of temperatures, as shown by its broad distribution in the eastern United States, but the suitability of the drier climate of California is unknown.  The weevil has been found in a relatively dry western state (Oklahoma), but the extent of its incursion there is unknown (Rebek and Grantham, 2008).

Conclusion and Rating Justification:

Pseudocneorhinus bifasciatus is a weevil that attacks a wide range of hosts.  If it can become established in California, it poses an economic and environmental threat to the state.  For these reasons, an “A” rating is justified.


Allen, H.W. 1957.  A Japanese weevil abundant in the Philadelphia area.  Entomological News 68: 169-174.

Allen, H.W. 1959. The Japanese weevil Pseudocneorhinus bifasciatus Roelofs. Journal of Economic Entomology 52: 586-587.

CDFA.  2015.  Detector dogs do it again!  Planting Seeds – Food & Farming News from CDFA. Accessed:  May 4, 2018

Cottrell, T.T. and Horton, D.L.  2013.  Emergence of root-feeding weevils (Coleoptera: Curculionidae) in central Georgia peach orchards.  Journal of Entomological Sciences 48: 184-194.

Day, E.R.  2014.  Japanese Weevil.  444-624 (ENTO-98NP).  VCE Publications. Virginia Cooperative Extension, Virginia Tech, and Virginia State University.

Gayeltshen, J. and Hodges, A.  2016.  Twobanded Japanese Weevil, Pseudocneorhinus bifasciatus Roelofs (Insecta: Coleoptera: Curculionidae).  EENY361.  Entomology and Nematology Department, University of Florida; IFAS Extension.

Maier, C.T.  1983.  Influence of host plants on the reproductive success of the parthenogenetic Two-Banded Japanese Weevil, Callirhopalus bifasciatus (Roelofs) (Coleoptera: Curculionidae).  Environmental Entomology 12: 1197-1203.

Rebek, E.J., and Grantham, R.  2008.  New Oklahoma insect pest of woody ornamentals: Japanese weevil.  Plant Disease and Insect Advisory.  Oklahoma State University Extension. Vol. 7, No. 33.

Smith, F.F. 1955. Scientific Notes: Notes on the biology and control of Pseudocneorhinus bifasciatus. Journal of Economic Entomology 48:628-629.

Symbiota Collections of Arthropods Network.  Accessed May 22, 2018.

Takenouchi, Y., Suomalainen, E., Saura, A., and Lokki, J.  1983.  Genetic polymorphism and evolution in parthenogenetic animals.  XII.  Observations on Japanese polyploid Curculionidae (Coleoptera).  Japanese Journal of Genetics 58:153-157.

Thomas, M.C. 2005. Pest Alert: The twobanded Japanese weevil (Pseudocneorhinus bifasciatus Roelofs), an invasive pest new to Florida (Coleoptera: Curculionidae).  Florida Department of Agriculture and Consumer Services.  DACS-P-01673.  Accessed: May 2, 2018.,_The_two_banded_Japanese_Weevil.pdf

Wheeler, A.G., Jr., and Boyd, D.W., Jr. 2005. Distribution of an invasive weevil, Pseudocneorhinus bifasciatus Roelofs, in the southeastern United States. Journal of

Entomological Science 40: 25-30.

Zepp, D.B.  1978.  Egg pod formation by Callirhopalus (subg. Pseudocneorhinus) bifasciatus (Roelofs) (Coleoptera: Curculionidae: Eremninae).  Coleopterists Bulletin 32: 311-313.

Photo: By Judy Gallagher [CC BY 2.0 (], via Wikimedia Commons


Karen Olmstead, Environmental Scientist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6879;

Responsible Party:

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

Comment Period:* CLOSED

7/25/18 – 9/08/18


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Pest Rating: A

Posted by ls