California Pest Rating for
South American Palm Weevil | Rhynchophorus palmarum (Linnaeus)
Pest Rating: B
PEST RATING PROFILE
On March 17, 2016 several adult and larval weevils collected by San Diego County officials during the removal of a Canary Island date palm in San Ysidro were identified as Rhynchophorus palmarum, South American palm weevil (SAPW) (PDR 370P06400129). Although SAPW has been found in this area since 2011 this is the first confirmation of a breeding population in California. A pest rating proposal is required to assign a permanent pest rating.
History & Status:
Background: Adult female SAPW are attracted to fresh trunk wounds of palm trees and lay their eggs inside a hole in the trunk that they have chewed1. After hatching, larvae bore into the tree where they feed on live and rotting tissue1. This feeding can eventually lead to death of the palm. SAPW adult females are known to vector the nematode Bursaphelenchus cocophilus (red ring nematode), which accelerates the death of the host palm1. Known reproductive hosts include: Arecaceae: Cocos nucifera (coconut), Elaeis guineensis (Afrian oil palm), Euterpe edulis (assai palm), Metroxylon sagu (sago palm), Phoenix canariensis (Canary Island date palm), Phoenix dactylifera (date palm); Poaceae: Saccharum officinarum (sugarcane)1. Adult weevils also feed on a wide variety of fruits and other plants but have never been documented to be a pest of these hosts. SAPW may be transported long distances when infested palm trees or palm parts are moved.
Worldwide Distribution: SAPW is native to Central and South America, and has spread northward throughout Mexico, presumably due to unrestricted movement of palm nursery stock. The beetle is now making incursions across the southern border of the United States into California, Arizona, and Texas.
Official Control: SAPW is listed as a harmful organism by Albania, Austria, Belgium, Bulgaria, China, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Holy See (Vatican City State), Honduras, Hungary, Indonesia, Ireland, Italy, Jamaica, Japan, Korea, Latvia, Lithuania, Luxembourg, Malta, Monaco, Montenegro, Morocco, Namibia, Netherlands, Poland, Portugal, Romania, San Marino, Serbia, Slovakia, Slovenia, South Africa, Spain, Sweden, Switzerland, Taiwan, Timor-Leste, and the United Kingdom2. Bursaphelenchus cocophilus, a nematode that is vectored by SAPW, is listed as a harmful organism by Antigua and Barbuda, Chile, China, Colombia, Dominica, Honduras, Jamaica, and Saint Lucia2.
California Distribution: SAPW has been found in southern San Diego and Imperial counties since 2011, and may have been flying into these areas from Mexico since 19661.
California Interceptions: SAPW has not been found in any regulatory situations in California.
The risk Rhynchophorus palmarum (SAPW) would pose to California is evaluated below.
Consequences of Introduction:
1) Climate/Host Interaction: SAPW can be expected to establish throughout California wherever suitable hosts are grown. The weevil is protected from the environment inside palms and is unlikely to be extirpated by cold weather. SAPW 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: SAPW is known to reproduce in seven species of plants in two plant families. Adult weevils also feed on a wide variety of food sources, including many fruits and other plants. However, it has only been documented to be a pest of palms and sugarcane. 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: SAPW has high reproductive rates. Each female can lay 120-150 eggs over a period of 30 days and the weevils can complete a generation in 80 days1. SAPW can fly a mile in 24 hours and may be transported long distances when infested palms or sugarcane are moved1. SAPW 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: As it expands its range in California, SAPW is likely to reduce yields in date groves and palm nurseries by destroying trees. The species might also increase crop production costs in date groves and lower the value of palm nursery stock. SAPW is considered a quarantine pest by many of California’s trading partners and has the potential to disrupt exports as a contaminating pest. SAPW is also known to vector the plant pathogenic nematode Bursaphelenchus cocophilus. SAPW receives a High (3) in this category.
Evaluate the economic impact of the pest to California using the criteria below. Score:
A, B, C, 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.
– 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: As it expands its range in California, SAPW is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes. The beetle is not likely to directly affect any threatened or endangered species or disrupt any critical habitats. SAPW may trigger new treatments by residents, by the nursery industry, and by date growers. Palm trees are an iconic ornamental plant in the California landscape and may be significantly impacted by this pest. SAPW receives a High (3) in this category.
Evaluate the environmental impact of the pest on California using the criteria below.
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 Common Name: 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: SAPW is only known to have established a localized distribution in southern San Diego County and to have made incursions into Imperial County. The species receives a Low (-1) 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.
The final score is the consequences of introduction score minus the post entry distribution and survey information score: High (14)
CDFA’s palm weevil trapping was mostly discontinued in 2013, and it is possible that Rhynchophorus palmarum has expanded its range in California since that time. The species may have additional host trees or switch hosts multiple times in California. The weevil could switch hosts and feed on native palms, which would disrupt natural communities. However, the weevils have significant populations in areas with many native Washingtonia palms and have not affected those trees. Unfortunately, there is one report of SAPW feeding on Washingtonia robusta in Mexico4.
Conclusion and Rating Justification:
SAPW is likely to have significant economic and environmental impacts as it expands its range in California. However, it is already found in southern San Diego and Imperial counties and is thought to regularly enter the state from Mexico. The weevil is not under official control (e.g., quarantine or eradication). There are no plans for federal agencies to take any action on this pest3. A “B”-rating is appropriate.
1 Rhynchophorus palmarum. USDA APHIS 2011. https://www.aphis.usda.gov/plant_health/plant_pest_info/palmweevil/downloads/Rhynchophoruspalmarum_v5.pdf
2 USDA Phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD). https://pcit.aphis.usda.gov/pcit/
3 Summary of Recommendations for Palm Weevils. 2013. The PPQ Palm Weevil Working Group (PWWG).
4 García-Hernández, José Luis, Luis Felipe Beltrán-Morales, José Guadalupe Loya-Ramírez, J.R. Morales-Cota, Enrique Troyo Diéguez, and Félix Alfredo Beltrán-Morales. 2003. Primer informe del Rhynchophorus palmarum (Coleoptera: Dryophthoridae) en Baja California Sur. Folia Entomol. Mex. 42(3): 415-417.
Jason Leathers, 2800 Gateway Oaks, Sacramento CA 95833, (916) 654-1211, plant.health[@]cdfa.ca.gov
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Pest Rating: B
Posted by ls