Gymnocoronis spilanthoides | Senegal tea plant

California Pest Rating for
Family: Asteraceae
Gymnocoronis spilanthoides – Senegal tea plant
Synonym- Alomia splanthoides (D. Don ex Hook & Arnott)
Pest Rating: A |  Proposed Seed Rating: P


Initiating Event:

This plant was recently intercepted by a county dog team in a USPS shipment from Arizona. The species has been listed as noxious by Australia due to its invasion potential in wet habitats and is under investigation by USDA APHIS.

History & Status:

Senegal tea plant is a long lived aquatic, broadleaved and herbaceous perennial plant that grows on damp ground or in shallowly submerged soil. It forms a rounded clump or a tangled mass of vegetation along waterways. Senegal tea plant is a weed of wetter tropical, sub-tropical and warm temperate environments. It is particularly problematic along streams, around lakes and dams, in swamps, wetlands and along drains and channels. It has been introduced into Australia and India by the Aquarium industry, as this plant is sometimes used for aquaria2.

Senegal tea plant is native to South America (Brazil, Peru, Argentina, Paraguay and Uruguay) and Mexico3. It grows very rapidly, up to 15 cm per week and its floating mats cover water bodies, block drainage channels and degrade natural wetlands2. The Weed Science Society of America (WSA) has noted that it is one of the 16 weeds not yet present in the United States that poses the greatest potential threat to its ecosystems2.

Official Control: Senegal tea plant is recognized as a harmful weed in the Republic of Korea6. It has been classified as a noxious weed in New Zealand and in Australia. It has been put on North American Plant Protection Organization’s (NAPPO) Phytosanitary Alert List. Importation of Senegal tea plant to Australia and New Zealand is not permitted because of the risk of further spread3. It has not yet established in California.

California Distribution: Senegal tea plant is not found spontaneously in California at this time.

California Interceptions: State exterior quarantine inspectors have intercepted this plant once in a shipment from Arizona10. It has not been found in the natural environment of California.

United States Distribution: Senegal tea plant is present in the United State aquarium trade and is sold online in the U.S.7. It has not been found in the natural environment in the United States.

International Range: Senegal tea plant is a native to South America (Brazil, Peru, Argentina, Paraguay and Uruguay) and Mexico. It is naturalized in Senegal, Hungary and parts of Asia, South America and Oceania. Recently, it is reported to be naturalized in irrigation canals and rice fields in Italy1.

This risk Senegal tea plant would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Risk is High (3). Senegal tea plant grows in humid tropics, subtropics and warm temperate regions where it forms dense floating mats, rooted in damp soil. It grows over the surface of slow moving or stationary water bodies, in wet marshy soils, wetlands and in degraded waterways. California’s Mediterranean climate with rainy winters and dry summers is similar to climate in Western Australia where this weed is recognized as invasive2. Senegal tea plant can become established if it is introduced to California through aquarium and nursery trade.

Score: 3

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

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: Risk is High (3) .Senegal tea plant does not require any one host, but grows where ecological conditions are favorable. It has the potential to grow in California due to its affinity to grow in regions with 20-100 inch precipitation and warmer summers7.

Score: 3

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 High (3). Senegal tea plant reproduces by seeds and vegetative means. It produces roots at the joints along the stems enabling new plants to grow from stems fragments. Seeds and stem fragments spread mainly by water. Seeds can accidentally spread in mud attached to the feet of animals. Stem fragments can also be spread easily by transport and machinery (e.g. boats, trailers, and lawnmowers). Another means of introduction to new areas is through unwise disposal (dumping) of aquarium plants in fresh water2, 4, 8.

Score: 3

Evaluate the natural and artificial 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). Senegal tea plant infestation can cause blockage of water ways and drainage channels leading to increased damage caused by flooding. When large amount of this plant die off and rot under water, the quality of water is compromised6. This plant is hard to kill, as herbicides can kill only the upper parts of the plant and plant parts beneath water are not killed. Below water plant material and silt can be removed by heavy machines3. Senegal tea plant is a rarely encountered aquarium plant and some plants from Southeast Asia are sold in California. Given the small number of plants involved, the income generated from such sales on an annual basis are unlikely to be significant, much less approaching the potential control costs following the successful invasion of California by this plant.

Score: 2

Evaluate the likely economic impacts of the pest to California using the criteria below.

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.

Score the pest for Environmental Impact:

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). Senegal tea plant can easily invade and degrade natural wetland ecosystems and waterways. It competes strongly with slower growing native plants and can eventually replace them. This in turn can affect wetland birds and animals which are dependent on these native plants for food and shelter. Senegal tea plant poses a significant threat to entire wetland ecosystems in Australia. This weed can quickly takes over wetlands and can detract from their environmental value, natural beauty and recreation potential. Since it’s found mainly in water, the herbicides used for control can potentially impact non target plants and animals4,8.

Score: 3

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:

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 Senegal tea plant:

Add up the total score and include it here. (14)

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

6) Post Entry Distribution and Survey Information: 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: 0

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. Final score: 14


California is suitable for the establishment of Senegal tea plant. However, the exact habitat for its establishment is not yet known. Based on the USDA APHIS weed risk assessment, this plant is in the aquarium trade and is cultivated in the United States (Anonymous, 2012; Extra Plant, 2012). This plant has the ability of rapid growth and spread in places with warm summers, rainy winter’s and the Marine West Coast.

Conclusion and Rating Justification:

Senegal tea plant is recognized as high alert weed in Australia and New Zealand. The European and Mediterranean Plant Protection Organization (EPPO) added this weed to its alert list in 2009.   It qualifies for an A rating, as it has invaded habitats in Australia that are similar to those found in California.


1Ardenghi, N. M. G., G. Barcheri, C. Ballerini, P. Cauzzi, and F. Guzzon. 2016. Gymnocoronis spilanthoides (Asteraceae, Eupatorieae), a new naturalized and potentially invasive aquatic alien in S Europe. Willdenowia 46:265-273. Last accessed 11/01/2016

2Invasive species compendium; Assessed date: 10/12/2016

3Weed Management Guide: Senegal Tea Plant- Gymnocoronis spilanthoides; Assessed date:10-12-2016

4Environmental weeds of Australia for Biosecurity Queensland: Gymnocoronis spilanthoides; Assessed Date:10-12-2016

5European and Mediterranean Plant protection Organization: Assessed date:10/12/2016

6USDA PCIT PeXD; Assessed Date: 10/12/2016

7Weed Risk Assessment for Gymnocoronis spilanthoides (D. Don ex Hook. & Arn.) DC. (Asteraceae) – Senegal Tea Plant; Assessed Date: 10/12/2016

8Global invasive species database; Assessed Date: 10/12/2016

9Fact sheet of Gymnocoronis spilanthoides – Weed Science Society of America, Assessed Date: 10/12/2016

10Pest and Damage Report Database; Plant Health and Pest Prevention Services, California Department of Food and Agriculture: Assessed Date: 10/12/2016

Worldwide distribution of Gymnocoronis spilanthoides (G. Fowler, USDA-APHIS-PPQ, Center for Plant Health Science and Technology)


Source: Weed Science Society of America (

Responsible Party:

Raj Randhawa, Senior Environmental Scientist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 654-0317;[@]

Comment Period:  CLOSED

45-day comment period: Nov 2 – Dec 17, 2016

Pest Rating: A |  Proposed Seed Rating: P

Posted by ls