Coco-Yam, Elephant Ear or Taro | Colocasia esculenta | Pest Rating Proposals and Final Ratings

California Pest Rating for

Colocasia esculenta : Coco-Yam, Elephant Ear or Taro

Family: Araceae

Pest Rating: D | Proposed Seed Rating: N/A

PEST RATING PROFILE

Initiating Event:

This plant has been rated as “Q” on the CDFA Plant Pest Rating since 2015.

History & Status:

Background: Colocasia esculenta is a tropical plant grown primarily for its edible corms. It is cultivated as a vegetable most commonly known as taro,Gabi and Abi or Avi. There are dozens of other common names used in other parts of the world including culcas from which the genus name Colocasia is derived; the descriptive anatomical name, elephant ear, eddo, imo, dasheen, coco-yam and malombo. It is believed to be one of the earliest cultivated plants².

Plants have been in cultivation for over 2,800 years as a food crop in equatorial regions including India, China, Southeast Asia, Indonesia, Polynesia, the Mediterranean, Africa, and South America. All parts of the plant are edible if they are thoroughly steamed or boiled to first remove calcium oxalate crystals.The cooked leaves are used in Hawaiian luaus and the corms are mashed into poi¹.

It was grown in Africa and was first brought to the Americas as a food crop for slaves. In 1910, Colocasia esculenta was promoted as an alternative crop to potatoes by the USDA⁵. There are more than 200 cultivars of taro, selected for their edible corms or cormels, or their tropical looking ornamental foliage². It is cultivated commercially on a small scale in the Central valley and Sacramento valley of California⁶.

Official Control: None at this time in California.

California Distribution: Colocasia esculenta is a perennial herb that is not native to California. It has been reported in the Delta in Sacramento, San Joaquin and Solano Counties. It also been found in Southern CA in Orange County³.

California Interceptions: Colocasia esculenta is occasionally sold in nurseries in CA. It is consumed as a vegetable in California and sold state-wide in produce markets.

United States: Colocasia esculenta is wide spread in the southeastern United States⁴. It is a most important source of food in the Hawaiian Islands.

Worldwide Distribution: Colocasia esculenta is an ancient crop grown throughout the tropic and sub-tropics. Because Colocasia esculenta has been in cultivation for so long, no one knows where it truly is native, but all evidence points to Southeast Asia. It is viewed as invasive in FL, HW, PR, Queensland, Cuba, Costa Rica and many of the Pacific Islands.

Consequences of Introduction:

1) Climate/Host Interaction: Risk is Medium (2), as Colocasia esculenta is naturalized in the marshy and watershed areas throughout southeastern America and is spreading there. It is established in one area of the Delta in California.

Evaluate if the pest would have suitable hosts and climate to establish in California:

Score: 2

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) Pest Host Range: Risk is High (3) as weeds do not require any one host, but grow wherever ecological conditions are favorable.

Evaluate the host range of the pest:

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: Risk is Medium (2) as the plant spreads vegetatively through rhizomes, stolons, offshoot corms or vegetative fragments.It does not seem to produce seed in CA.

Evaluate the dispersal potential of the pest:

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: Risk is Medium (2) as Colocasia produces 2.5′ wide by 3.5′ long leaves with up to 30″ tall patch that could lower the crop yield due to shading and changes in the cultural practices where it is established.

Evaluate the economic impact of the pest to California using these criteria:

Economic Impact: A, D

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 by other states or countries)

D. The pest could negatively change normal production cultural practices

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: Risk is High (3) as it invades wetland edges, swamps, blackwater streams, lakes and disrupt natural wetland communities of California. It is established in a state park where it forms a dense thicket at the wetland interface; this will encourage treatment for control. If it spreads, it could affect populations of sensitive species such as Mason’s lilaeopsis (Lilaeopsis masonii), CA Clapper rail (Rallus obsoletus), Suisun aster (Symphyotrichum lentum) and Delta tula pea (Lathyrus jepsonii).

Evaluate the environmental impact of the pest on California using the following criteria:

Economic Impact: A, C, D

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. Significantly impacting cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

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 Colocasia esculenta :

Rating (Score): Add up the total score and include it here:

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

Total points based on above criteria, which does not take into account the pathogen’s already wide distribution in California: Medium (12).

6) Post Entry Distribution and Survey Information: 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:

Score: Low (–1)

-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: (11)

Uncertainty:

This plant has been known in Southeastern America for over 100 years and spreading colonies have been detected.So, there is low uncertainty that it will continue to spread in wetlands of California.

Conclusion and Rating Justification:

Proposed Rating: based on the score listed above, the pest is Medium risk for further invasions of California. It has a potential to invade the wet areas of California, and it is already reported in 4 counties. Nevertheless, as Colocasia esculenta is an agricultural commodity in California, a “D” rating is justified.

References:

1. Avent Tony and Carey Dennis, (2016). Cool Colocasias; Plant Delights Nursery, Inc. Accessed 11-15-2016.

http://www.plantdelights.com/Article/Colocasia-Elephant-Ears

Colocasia esculenta, Encyclopedia of Life.Eol community website .

http://www.eol.org/pages/1091931/overview

Calflora: Information on California plants for education, research and conservation, with data contributed by public and private institutions and individuals, including the Consortium of California Herbaria. 2016. Berkeley, California. Accessed 11-15-2016.

http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=13042

Federal database with information on identification and distribution, and links to websites in individual states. Accessed 11-15-2016.

http://plants.usda.gov/core/profile?symbol=COES

Swearingen, J., C. Bargeron. 2016 Invasive Plant Atlas of the United States. University of Georgia Center for Invasive Species and Ecosystem Health

http://www.invasiveplantatlas.org/subject.html?sub=5369

Taro root (colocasia esculenta) reported Naturalizing in ca;ifornia by CA State Parks.

http://www.cal-ipc.org/symposia/archive/pdf/2014/Poster2014_Robison.pdf

Responsible Party:

Javaid Iqbal, California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6695; plant.health[@]cdfa.ca.gov.

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