Nymphoides peltata | Pest Rating Proposals and Final Ratings

California Pest Rating for

**Yellow Floating-heart Nymphoides peltata (Gmel.) Kuntze**

Pest Rating: A | Proposed Seed Rating: R

PEST RATING PROFILE

Initiating Event:

There is a recent detection of Yellow Floating-heart found growing in Los Angeles County. This is the third detection of this species occurring spontaneaously in California and the only recent one.

History & Status:

Background: Yellow Floating-heart is an aquatic plant of the family Menyanthaceae native to Eurasia. It has cordate floating leaves that support a lax inflorescence of yellow flowers with fringed petal margins. The fruit is a capsule bearing many flattened seeds with stiff marginal hairs. It has adventitious roots along an underwater stem. Like many aquatic plants, Yellow Floating-heart can reproduce vegetatively and spread over large areas of water. Because it has floating leaves it can photosynthesize rapidly and outcompete many other aquatic plants. Yellow Floating-heart aggressively colonizes in lakes, riparian zones, water courses, and other wetlands.

Little information is available on the control of Yellow floating-heart. Based on the plant’s characteristics, mechanical and hand removal would likely be effective. It is not known whether biological or chemical controls are effective on Yellow Floating-heart. New Zealand information suggests that hand clearing is possible with small infestations and herbicides need to be used for larger infestations.

Worldwide Distribution: Yellow floating-heart is native to Eurasia and it is naturalized in New Zealand, Great Britain, North America, and Australia. In the U.S. it has been found in 25 states, including CA, TX, WA, & AZ.

California Distribution: Yellow Floating-heart has been found in very limited areas of El Dorado, Del Norte, Monterey, and Los Angeles Counties.

California Interceptions: Yellow Floating-heart is occasionbally sold in nurseries in CA as a pond plant and this is the most likely pathway for introduction into the environment.

This risk Yellow Floating-heart would pose to California is evaluated below:

Consequences of Introduction:

1) Climate/Host Interaction: 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

Risk is Medium (2) as illustrated by the localized range of the plant in states where it occurs. Yellow Floating-heart would be expected to colonize riparian areas, ponds, wetlands, roadside ditches, irrigation canals, and shallow lake margins.

2) Pest Host Range: Evaluate the host range of the pest: 3

– Low (1) has a very limited host range
– Medium (2) has a moderate host range
– High (3) has a wide host range

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

3) Pest Dispersal Potential: 2. 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

Risk is Medium (2) as the plant spreads via water flow and escape from yard water features. Once established it can spread quickly.

4) Economic Impact: 2. Evaluate the economic impact of the pest to California using these criteria:

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

-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

Risk is Medium (2) as Yellow Floating-heart lowers can impede water flow in irrigation canals, as well as interfere with navigation.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the following criteria:

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: 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

Risk is High (3) in California, as Yellow Floating-heart is an aggressive invader of wetlands. As such, it displaces native plant species in these important habitats. Species outcompeted and excluded potentially include such state and federal endangered plants as, Bogg’s Lake hedge hyssop and Gambell’s watercress. Potential effects on endangered wildlife include breeding habitat modification, and food disruption (either directly from food plant exclusion, or indirectly via insect prey reduction). Potentially affected species include the Point Arena mountain beaver, red-legged frog, yellow-legged frog, and California tiger salamander.

Consequences of Introduction to California for Nymphoides peltata

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 pest’s 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: -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:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (11)

Uncertainty:

This plant entered California long ago, but this is the first find in over a decade. It is not known how far its spread will extend. Shallow water habitat represents a small percentage of habitat in California, but it is widespread throughout the state and is disproportionally important due to its water availability and importance for agriculture and wildlife. Given the limited distribution of this plant, it may be possible to eradicate it at this time. Although it has not yet spread widely, there is nothing to stop it spreading in the appropriate habitats.

Conclusion and Rating Justification:

Conclusions of the harm(s) associated with this pest to California using all of the evidence presented above: Proposed Rating: Based on the score listed above the pest is a Medium risk. As the plant is limited to small areas at this time, prompt and effective action would have a signifiant effect on the future impacts of this species. Therefore, a rating of “A”is proposed.

Literature:

USDA Plants. Accessed 10/15/15: https://plants.usda.gov/core/profile?symbol=NYPE

Washington State Weed website. Accessed 10/15/15: Dept of Ecology; State of WA. Non-native Invasive Freshwater Plants:Yellow Floating Heart (Nymphoides peltata). http://www.ecy.wa.gov/programs/wq/plants/weeds/floatingheart.html

Responsible Party:

Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 654-0312; plant.health[@]cdfa.ca.gov.