Kidneyleaf mud plantain | Pest Rating Proposals and Final Ratings

California Pest Rating for

Kidneyleaf mud plantain | Heteranthera reniformis

Liliales: Pontedriaceae

Pest Rating: A | Proposed Seed Rating: P

PEST RATING PROFILE

Initiating Event:

Heteranthera reniformis has a current rating of Q. A pest rating proposal is required to designate a permanent rating for this species.

History & Status:

Background: Heteranthera reniformis, commonly known as kidneyleaf mud plantain is native to the fresh water wetlands of eastern North, Central and South America (Arakaki, Derek 2013). It is submerged or floating, annual or facultative perennial plant that grows 15-20 cm tall in fresh water less than 15 cm deep and on damp soil at water’s edge. The stems can grow along the mud under the water, with leaves and stems emerging. Roots occur at nodes along the stems (NSW Weedwise 2014). In North America, its flowering mainly starts in July, but the plant can flower from late May to September and can continue until frost (Csurhes, Steve 2016). This species has been listed as endangered in the states of Illinois and Ohio (USDA Natural Resource Conservation District, 2017).

H. reniformis prefers open, sunny sites with nutrient rich soils. It is commonly found in roadside ditches and in wet soils, on edges of fresh water streams, rivers and ponds, on fresh water tidal mudflats and along powerline corridors (Business Queensland, 2016). This species can grow rapidly to form dense mats when competition is low, but it is a poor competitor with taller sedges and rushes. It will grow well for a few years on the edges of the ponds and marshes before being shaded out. Since its stems can produce roots at each node, any broken segments with more than one node can be washed downstream to infest new areas (Csurhes, Steve 2016).

Worldwide Distribution: Heteranthera reniformis is naturalized in Italy, Spain and Australia. It is also distributed in parts of Mexico, Dominican Republic, Jamaica, Belize, Costa Rica, El Salvador, Honduras, Nicaragua, Panama, Guatemala, Columbia, Puerto Rico, Ecuador, Argentina, Brazil, Peru, Venezuela and Paraguay (Pacific Island Ecosystem at Risk, 2009). It has been found growing on the borders of rice fields in northern Italy (Csurhes, Steve 2016).

US Distribution: North Central US: Illinois, Missouri; Northeastern US: Connecticut, Indiana, New Jersey, New York, Ohio, Pennsylvania, West Virginia; South Central US: Texas; Southeastern US: Alabama, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, South Carolina, Tennessee, Virginia. (GRIN Taxonomy Database). There are approximately 200 collection sites listed in herbarium records for Heteranthera reniformis. Documented occurrences exist in: New York (22), West Virginia (5), Ohio (1), Illinois (2). It is also reported in Alabama (1), Arkansas (six counties), Georgia (5), Iowa (one county), North Carolina (two, maybe twelve, counties), South Carolina (3) (Nature Serve 2015).

Official Control: Heteranthera reniformis is considered as high risk weed in Hawaii (Arakaki, Derek 2013) and is a weed of special concern in Connecticut (USDA Natural Resource Conservation District, 2017). It is listed as an agricultural weed, spreading in Europe (Csurhes, Steve 2016). This species is also listed as weed in Portugal and Spain (Global Compendium of Weeds 2007).

California Distribution: Heteranthera reniformis was found once in Glenn County at the national wildlife reserve in 2011 (PDR# 1597375) (CDFA Pest and Damage Records Database, 2017).

California Interceptions: Hateranthera reniformis has not been intercepted through regulatory pathways by CDFA.

The risk Hateranthera reniformis, Kidneyleaf mud plant, would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Heteranthera reniformis grows in roadside ditches, on the edges of fresh water streams/rivers and ponds, in fresh water tidal mudflats, sinkholes, along powerline corridors and at an elevation of up to 2600 m in its native range. It has a strong potential to grow in similar areas of California but it would be limited to freshwater wetland and shallow water margins. Favorable conditions for its growth and expansion include recently inundated areas following flooding, beaver dams, rice fields or human activities in the state (Nature Serve 2015). It receives a Medium (2) in this category.

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: Heteranthera reniformis does not require one particular host but grows wherever ecological conditions are favorable. However, it is a poor competitor with many sedges, rushes and other wetland species and can be easily crowded out of wetlands (Pacific Island Ecosystem at Risk 2009). It receives a Medium (2) in this category.

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: Heteranthera reniformis reproduces both vegetatively and by seed. Its stem fragments can produce root at each node and produce new plants. These stem fragments can be washed downstream and infest new areas. A single flood event is likely to disperse stem fragments over a considerable distance. Each fruit contain 8-14 winged seeds and these seeds are likely dispersed by winds and water. Seed banks may persist in soil for many years. Plant fragments can also move to new location in mud stuck to animals or vehicles (NSW Weedwise 2014, Csurhes, Steve 2016). It receives a High (3) in this category.

Evaluate the natural and artificial dispersal potential of the pest:

Score: 3

– 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: Heteranthera reniformis is reported as a weed of flooded rice where yield reduction of up to 70% have been recorded in experimental plots (Csurhes, Steve 2016). In Hawaii, this species has already proved to be a problematic species in Oahu taro fields and may outcompete newly planted taro, resulting in reduced yields (Arakaki, Derek 2013). If reniformis were to introduce and establish in California, it is likely to impact rice growing areas of Sacramento and northern San Joaquin valley counties. Since it can cover shallow water surfaces, it is likely to interfere with water supply to irrigation fed agricultural areas. Use of herbicides to control infestations is likely to increase crop production costs in rice growing areas of California. It receives a High (3) in this category.

Economic Impact: A, B, G

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: 3

– 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: Heteranthera reniformis is likely to form dense mats and colonize open shallow waters in disturbed wetlands of California. This can make this weed a potential threat to state’s native vegetation and fresh water aquatic habitats. Its preferred habitat of sunny sites, nutrient rich soils and shallow water is present in Northern and Central coast of California; this makes it easy to grow and establish in those areas. It can grow quickly in recently inundated areas, where there is little competition with natives. It can persist and exclude natives in these situations. If it establishes, mechanical removal and need of herbicide applications can trigger additional chemical treatments. 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

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 Heteranthera reniformis, Kidneyleaf mud plant: High (13)**

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: Heteranthera reniformis has been found once growing in natural environment of California and 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:

Score: -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: Medium (12)

Uncertainty:

Although Heteranthera reniformis can grow rapidly in fresh water and on damp soils but it does not grow well in shaded areas and does not compete well with tall sedges and rushes. Early detection and surveys in fairly disturbed habitats, along ditches and margins of ponds and open mudflats in California may confirm the distribution of this species. Similar species such as H.limosa and the non-native H.rotundifolia complicate identification. Therefore it may be more widespread than is currently known.

Conclusion and Rating Justification:

Heteranthera reniformis is a medium risk weed and has a broad native range, from tropical to sub-tropical areas. This species thrives in various habitats and can become highly invasive, especially when the competition is low. If this species spreads in California, it can quickly dominate disturbed and wetland land habitats. An “A” rating is justified, as eradication is possible with attention to management.

References:

Arakaki, Derek. 2013. Pest Advisory No. 13-0. Hawaii Department of Agriculture. Accessed: 02/15/2017 https://hdoa.hawaii.gov/pi/files/2013/01/Heteranthera-reniformis.pdf

Business Queensland. 2016. Weeds and Diseases. Kidneyleaf mudplantain. Accessed: 02/15/2017 https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/land-management/health-pests-weeds-diseases/weeds-diseases/other/kidneyleaf-mudplantain

Csurhes, Steve. 2016. Invasive plant risk assessment: Kidneyleaf mudplantain. Department of Agriculture and Fisheries. Biosecurity Queensland. Accessed: 02/15/2017 https://www.daf.qld.gov.au/__data/assets/pdf…/IPA-Kidneyleaf-Risk-Assessment.pdf

Nature Serve. 2015. NatureServe Explorer: An online encyclopedia of life [web application. NatureServe, Arlington, Virginia. Accessed: 02/15/2017 http://explorer.natureserve.org

NSW Weedwise 2014. Department of Primary Industries. Kidney-leaf mud plantain. Accessed: 02/14/2017 http://weeds.dpi.nsw.gov.au/Weeds/Details/188

Randell, Rod 2007. Global Compendium of Weeds. Heteranthera reniformis (Pontederiaceae). Accessed: 02/14/2017 http://www.hear.org/gcw/species/heteranthera_reniformis/

Pacific Island Ecosystem at Risk (PIER) 2009. PIER Species lists: Heteranthera reniformis. Accessed: 02/14/2017 http://www.hear.org/pier/species/heteranthera_reniformis.htm

Pest and Damage Record Database, Plant Health and Pest Prevention Services, CA Department of Food and Agriculture. Assessed Date: 02/13/2017 https://pdr.cdfa.ca.gov/PDR/pdrmainmenu.aspx

USDA Natural Resource Conservation District. 2017. Plant profile: Heteranthera reniformis Ruiz & Pav. Accessed: 02/13/2017 https://plants.usda.gov/core/profile?symbol=HERE

US National Plant Germplasm System. GRIN Taxonomy Database. Heteranthera reniformis Ruiz and Pav. Accessed: 02/16/2017 https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.asp

Author:

Raj Randhawa, California Department of Food and Agriculture

Responsible Party:

Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 654-0317; plant.health[@]cdfa.ca.gov.