Weevil | Dryophthorus homoeorhynchus Perkins | Pest Rating Proposals and Final Ratings

California Pest Rating for

Dryophthorus homoeorhynchus Perkins: weevil

Coleoptera: Dryopthoridae

Pest Rating: C

PEST RATING PROFILE

Initiating Event:

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

History & Status:

Background: This beetle is black in color, elongate, and 4.5-6 mm in length. The species has a short rostrum (“beak”) (Perkins, 1900). Larvae of all species of Dryophthorus, including D. homoeorhynchus, apparently feed on rotting plant material, primarily wood. Dryophthorus homoeorhynchus is reported to feed on decomposing Chrysodracon species (Dracaenaceae) in Hawaii (Swezey, 1931; Swezey, 1954; Wagner et al., 2005). Other species in the genus are reported to feed on rotting hardwood and conifer wood, and at least one species has been reported to feed on rotting tree fern fronds (Hawaiian Entomological Society, 1928; O’Brien, 1997).

Worldwide Distribution: This beetle is native to, and is only known to occur in Hawaii. The species has been reported from Hawaii, Oahu, Maui, and Molokai islands (Natural Resources Conservation Service, 2009; Swezey, 1954).

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

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

California Interceptions: This beetle was intercepted on pineapple from Hawaii in February 2004 (California Department of Food and Agriculture).

The risk Dryophthorus homoeorhynchus would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Dryophthorus homoeorhynchus is only known to occur in Hawaii. If this beetle requires the climate found in its current area of distribution, then only a small portion of California would offer a similar suitable climate. At least one species in the family Dracaenaceae, Dracaena draco, is grown as an outdoor plant in California and could possibly serve as a host plant for homoeorhynchus. Due to the apparent climate restrictions, it appears unlikely that this beetle could become established in more than a small portion of California. Therefore, D. homoeorhynchus receives a Low (1) 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: Dryophthorus homoeorhynchus is only known to feed on the genus Chrysodracon. Therefore, it receives a Low (1) 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: The biology of homoeorhynchus is poorly known. The beetle is assumed to fly. 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: This beetle is only known to feed on dead plant material, as are all other members of the genus. Negative economic impacts are unlikely if this beetle became established in California. The species apparently feeds on decomposing plant material, not freshly-cut wood, and is known to be restricted to plants in the family Dracaenaceae, therefore there is little risk to timber. Therefore, it receives a Low (1) in this category.

Economic Impact:

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: Negative environmental impacts of this species if it became established in California appear minimal. The species feeds on dead plant material, and it appears to be restricted to a family of plants, the Dracaenaceae, that do not include any native California species. Therefore, it receives a Low (1) in this category.

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

Environmental Impact:

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: 1

– 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 Dryophthorus homoeorhynchus: Low (6)**

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: Dryophthorus homoeorhynchus 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: Low (6)

Uncertainty:

Dryophthorus homoeorhynchus may be able to tolerate cooler temperatures than are present in its native distribution. If this is the case, the species could become established over a greater portion of California if suitable plant material is present. The beetle may also be able to feed on plants in families other than Dracaenaceae. Feeding on living plant tissue, however, has not been reported in Hawaii and apparently all species in the genus Dryophthorus feed on dead, rotting plant tissue.

Conclusion and Rating Justification:

Dryophthorus homoeorhynchus is a tropical/subtropical beetle that feeds on dead plants in the family Dracaenaceae, and it is a member of a genus that is apparently restricted to dead, rotting plant material. This beetle appears to pose no threat, economic or environmental, to California. For these reasons, a “C” rating is justified.

References:

California Department of Food and Agriculture. Pest and damage record database. Accessed March 22, 2018. https://pdr.cdfa.ca.gov/PDR/pdrmainmenu.aspx

Hawaiian Entomological Society. 1928. January 6, 1927; notes and exhibitions. Proceedings of the Hawaiian Entomological Society. 7: 1-31.

Natural Resources Conservation Service. 2009. At-risk species and habitats lists. Biology Technical Note. 22: 1-403.

O’Brien, C.W. 1997. A catalog of the Coleoptera of America north of Mexico. Family: Curculionidae. Subfamilies: Acicnemidinae, Cossoninae, Rhytirrhininae, Molytinae, Petalochilinae, Trypetidinae, Dryophthorinae, Tachygoninae, Thecesterninae. United States Department of Agriculture. 48 pp.

Perkins, R.C.L. 1900. II. Coleoptera Rhyncophora, Proterhinidae, Heteromera and Cioidae. 117-270 in (D. Sharp, ed.) Fauna Hawaiiensis. Cambridge University Press. London. 579 pp.

Swezey, O.H. 1931. Some new records of insects on Molokai. Proceedings of the Hawaiian Entomological Society. 7: 485-488.

Swezey, O.H. 1954. Forest entomology in Hawaii. Bernice P. Bishop Museum Special Publication. 44: 1-265.

Symbiota Collections of Arthropods Network. Accessed March 20, 2018. http://scan1.acis.ufl.edu

Wagner, W.L., Herbst, D.R., and Lorence, D.H. 2005. Flora of the Hawaiian Islands. Accessed March 20, 2018. http://botany.si.edu/pacificislandbiodiversity/hawaiianflora/index.htm

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

Comment Period:* CLOSED

4/30/18 – 6/14/18

*NOTE:

You must be registered and logged in to post a comment. If you have registered and have not received the registration confirmation, please contact us at plant.health[@]cdfa.ca.gov.

Comment Format:

♦ Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction: 1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦ Posted comments will not be able to be viewed immediately.

♦ Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦ Comments may be edited prior to posting to ensure they are entirely germane.

♦ Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.