California Pest Rating Proposal for
Palmetto weevil | Rhynchophorus cruentatus (Fabricius)
Current Pest Rating: Q
Proposed Pest Rating: A
Comment Period: 7/3/18 – 8/17/18
Rhynchophorus cruentatus is currently Q-rated. A permanent pest rating proposal is required to support an official pest rating.
History & Status:
Background: Adult R. cruentatus are large weevils that measure 2.7 to 3.3 centimeters in length (Wattanapongsiri, 1966). They are dull to shining and reddish-brown to black (or a pattern of both) in color (Giblin-Davis et al., 1994). This species attacks palms. Eggs are laid in petiole bases or wounds in the palm. The larvae feed on the tissue internally and form a cocoon made from plant fiber, in which they pupate. The feeding damage can compromise the structural integrity of the palm to the extent that the crown falls over (Giblin-Davis and Howard, 1988). The larval feeding damage is cryptic because it occurs inside the palm, and it is often not apparent until death of the tree is inevitable (Hunsberger et al., 2000). In the case of Sabal palmetto, which is native in the beetle’s area of distribution, R. cruentatus apparently only attacks stressed trees. However, in the case of introduced palm species, including Phoenix canariensis, apparently healthy trees are attacked and killed, sometimes in large numbers. For example, 97% of the Phoenix canariensis in one Florida nursery were killed; the damage was estimated at $285,000-$380,000 (Hunsberger et al., 2000). Besides Phoenix and Sabal, other genera of palms reported to be attacked include Caryota, Cocos, Latania, Pritchardia, Roystonea, Thrinax, and Washingtonia (Hunsberger et al., 2000; Weissling and Broschat, 1999). Other non-palm plants may also be utilized by this beetle, but little information is available regarding this (Wattanapongsiri, 1966).
Other Rhynchophorus species are important palm pests, for example R. ferrugineus and R. palmarum. Rhynchophorus palmarum is a vector of the nematode Bursaphelenchus cocophilus, which causes red ring disease of palms. This nematode is not yet known to occur in the United States. The disease affects Phoenix dactylifera and P. canariensis, which are important crop and ornamental trees in California (Hodel, 2016). If this nematode was introduced to the United States, R. cruentatus could possibly vector it (Griffith, 1987).
Worldwide Distribution: Rhynchophorus cruentatus is native to the southeastern United States and is found from South Carolina south to Florida (including the Florida Keys) and west to Texas. The species has also been reported from the Bahamas (Andros Island), which may represent an introduction (Turnbow and Thomas, 2008; Wattanapongsiri, 1966).
Official Control: Rhynchophorus cruentatus is not known to be under official control anywhere.
California Distribution: Rhynchophorus cruentatus is not known to be present in California (Symbiota Collections of Arthropods Network).
California Interceptions: Rhynchophorus cruentatus was intercepted at a border station on palm fronds from Florida in 2011 (CDFA Pest and Damage Report Database, 2018).
The risk Rhynchophorus cruentatus would pose to California is evaluated below.
Consequences of Introduction:
1) Climate/Host Interaction: Two other Rhynchophorus species that are native to the tropics, ferrugineus and R. vulneratus, have become established in areas that do not have tropical climates, including Mediterranean Europe and southern California. Rhynchophorus cruentatus is found in the temperate to subtropical southeastern United States. Considering the climatic flexibility of other species in the genus, it seems likely that a significant portion of California could offer a suitable climate for R. cruentatus. Regarding host plants, palms (including known host species, such as Phoenix canariensis) are planted widely in California. Therefore, Rhynchophorus cruentatus 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: Rhynchophorus cruentatus is reported to feed on eight genera of palms. 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: Rhynchophorus cruentatus fly (Weissling et al., 1994). The species could also possibly be moved with palms, both whole plants as well as fronds. 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: Rhynchophorus cruentatus attacks palms, including the genera Phoenix and Washingtonia. If this beetle became established in California, it would threaten the date industry in southeastern California and (in a much larger area) ornamental palms. Ornamental palms are a $70 million industry in California and date production in the state was approximately $47 million in 2016 (Hoddle). By killing trees, cruentatus would lower yield in both industries. As mentioned above, in Background, R. cruentatus could possibly vector the nematode that causes red ring disease in palms. Therefore, it receives a Medium (2) in this category.
Economic Impact: A, 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: 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: Rhynchophorus cruentatus is reported to attack Washingtonia Groves of the native W. filifera are present in the deserts of southern California, and they could be threatened by the establishment of R. cruentatus. Palms that are known hosts of R. cruentatus, including Phoenix and Washingtonia species, are widely planted in California. If R. cruentatus became established in the state, it could impact home and urban plantings of these trees, and this could trigger treatment programs. 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, 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 Rhynchophorus cruentatus: Medium (11)
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: Rhynchophorus cruentatus 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.
7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (11)
The demonstrated ability for other Rhynchophorus species that are native to tropical areas to invade temperate areas (e.g., Europe) is considered to be evidence that R. cruentatus could possibly become established in California, even though this species is currently known to occur in areas with a subtropical or tropical climate. Rhynchophorus cruentatus has not been proven to vector the nematode B. cocophilus. The desert areas where the native groves of Washingtonia filifera occur may not have a suitable climate for the establishment of R. cruentatus. If so, these native palm groves are not at risk from this beetle.
Conclusion and Rating Justification:
Rhynchophorus cruentatus feeds on and kills palm trees, and it is not known to be present in California. This species poses a threat to the economy and environment of the state. For these reasons, a “A” rating is justified.
CDFA Pest and Damage Report Database. 2018. Rhynchophorus cruentatus. Plant Health and Pest Prevention Services. CA Department of Food and Agriculture. Accessed April 11, 2018: https://pdr.cdfa.ca.gov/PDR/pdrmainmenu.aspx
Giblin-Davis, R. M. and Howard, F. W. 1988. Notes on the palmetto weevil, Rhynchophorus cruentatus (Coleoptera: Curculionidae). Proceedings of the Florida State Horticultural Society 101:101-107.
Giblin-Davis, R. M., Weissling, T. J., Oehlschlager, A. C., and Gonzalez, L. M. 1994. Field response of Rhynchophorus cruentatus (Coleoptera: Curculionidae) to its aggregation pheromone and fermenting plant volatiles. Florida Entomologist 77:164-172.
Griffith, R. 1987. Red ring disease of coconut palm. Plant Disease 71:193-196.
Hoddle, M. Has the South American palm weevil, Rhynchophorus palmarum, established in southern California? University of California, Riverside, Center for Invasive Species Research. Accessed November 17, 2017: http://cisr.ucr.edu/palmarum.html
Hodel, D. R., Marika, M. A., and Ohara, L. M. 2016. The South American palm weevil. PalmArbor 2016-3:1-27.
Hunsberger, A. G. B., Giblin-Davis, R. M., and Weissling, T. J. 2000. Symptoms and population dynamics of Rhynchophorus cruentatus (Coleoptera: Curculionidae) in Canary Island date palms. Florida Entomologist 83:290-303.
Symbiota Collections of Arthropods Network. Accessed April 11, 2018. http://scan1.acis.ufl.edu
Turnbow, R. H. and Thomas, M. C. 2008. An annotated checklist of the Coleoptera (Insecta) of the Bahamas. Insecta Mundi 34:1-64.
Wattanapongsiri, A. 1966. A Revision of the Genera Rhynchophorus and Dynamis (Coleoptera: Curculionidae). Ph.D. thesis. Oregon State University.
Weissling, T. J. and Broschat, T. K. 1999. Integrated management of palm pests. Proceedings of the Florida State Horticultural Society 112:247-250.
Weissling, T. J., Giblin-Davis, R. M., Center, B. J., and Hiyakawa, T. 1994. Flight behavior and seasonal trapping of Rhynchophorus cruentatus (Coleoptera: Curculionidae). Annals of the Entomological Society of America 87:641-647.
Kyle Beucke, 1220 N Street, Room 221, Sacramento, CA, 95814, 916-403-6741; plant.health[@]cdfa.ca.gov.
Jason Leathers, 2800 Gateway Oaks, Sacramento CA 95833, (916) 654-1211, plant.health[@]cdfa.ca.gov
7/3/18 – 8/17/18
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