California Pest Rating for
Tarophagus colocasiae (Matsumura): Taro Planthopper
Hemiptera: Delphacidae
Pest Rating: B
PEST RATING PROFILE
Initiating Event:
Tarophagus colocasiae is commonly intercepted by California’s high risk programs. This planthopper is currently assigned a temporary rating of “Q” and is therefore in need of a permanent pest rating.
History & Status:
Background: Tarophagus colocasiae is a planthopper that is considered a serious pest of taro (Colocasia esculenta)1. The planthopper feeds by sucking sap and/or xylem from the plant tissue1. Feeding produces honeydew, sooty mold, and necrotic areas on leaves and discoloration of bark on stems1. Heavy infestations may cause stunting and/or wilting of the taro plants. Taro planthopper is also reported to vector alomae and bobone diseases, which are caused by rhabdoviruses, between taro plants. The planthopper may spread long distances by the movement of infested taro plants, leaves, or roots.
Worldwide Distribution: Tarophagus colocasiae is widespread in Southeast Asia and the Pacific islands1. It has been present in Hawaii since at least 1930. The planthopper was confirmed to be present in Florida in June 2015 and is likely established in both Jamaica and Cuba4.
Official Control: Tarophagus colocasiae is not listed as a quarantine pest by any other states or nations2. However, Tarophagus proserpina is listed as a quarantine pest by Japan and Korea and that species may be a synonym of T. colocasiae.
California Distribution: Tarophagus colocasiae has never been found in the environment of California.
California Interceptions: Between January 1, 2000 and January 6, 2015, Tarophagus colocasiae was intercepted 133 times on consignments from Hawaii. 127 of the interceptions were on taro. The remainder were on betel leaf (1), ginger (1), galanga (2), and sweet potato (2).
The risk Tarophagus colocasiae (taro planthopper) would pose to California is evaluated below.
Consequences of Introduction:
1) Climate/Host Interaction: Taro grows in USDA plant hardiness zones 8 through 11 and is grown in gardens and small-scale commercial farms in Fresno and Sacramento California3. Tarophagus colocasiae is expected to be able to establish wherever these plants are grown. It receives a Medium (2) 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: Tarophagus colocasiae is only known to feed on taro and related aroids. It receives a Low (1) 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: Taro planthoppers may be moved long distances when infested taro plants, leaves, or roots are moved. However, their wings do not fully develop and they are not considered to be good fliers. Planthoppers have high reproductive rates. Tarophagus colocasiae 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: If Tarophagus colocasiae were to establish in California it would be likely to lower the yield of commercial taro farms and gardens. The planthopper would also be likely to increase crop production costs. Taro leafhopper may also vector diseases between taro plants. It receives a High (3) in this category.
Evaluate the economic impact of the pest to California using the criteria below. Score:
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: Tarophagus colocasiae is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes. Taro planthopper is not expected to directly affect threatened or endangered species or disrupt critical habitats. The planthopper may trigger additional treatment programs by gardeners and growers of commercial taro. The planthopper may also significantly impact taro plants in home/urban gardens. Taro planthopper 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 Tarophagus colocasiae (Taro Planthopper): Medium(12)
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: Tarophagus colocasiae 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: Medium(12)
Uncertainty:
Tarophagus colocasiae is frequently intercepted. Presumably, the planthopper sometimes escapes detection and enters California. There have not been any formal surveys for the pest in the state, so it is possible that it may have established in some locations.
Conclusion and Rating Justification:
Tarophagus colocasiae has never been found in the environment of California. However, if it were to enter the state economic and environmental impacts would be limited to taro plants in home gardens and small-scale commercial farms. A “B” rating is justified.
References:
1CABI Plantwise Knowledge Bank. http://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=52786
2 USDA Phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD). https://pcit.aphis.usda.gov/pcit/
3Robinson, Ramona and Cara Allen. 2014. Taro root (Colocasia escuelenta) reported naturalizing in California. California Department of Parks and Recreation. http://www.cal-ipc.org/symposia/archive/pdf/2014/Poster2014_Robison.pdf
4 Halbert, Susan E. and Charles R. Bartlett. The taro planthopper, Tarophagus colocasiae (Matsumura), a new delphacid planthopper in Florida. Florida Department of Agriculture and Consumer Services Pest Alert. http://www.freshfromflorida.com/Divisions-Offices/Plant-Industry/Plant-Industry-Publications/Pest-Alerts/Tarophagus-colocasiae
Responsible Party:
Jason Leathers, 1220 N Street, Sacramento, CA, 95814, (916) 654-1211, plant.health[@]cdfa.ca.gov.
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Pest Rating: B
Posted by ls
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