Aeschynomene spp | Pest Rating Proposals and Final Ratings

California Pest Rating for

Jointvetch | Aeschynomene spp.

Rosidae; Fabales; Fabaceae

Pest Rating: A | Proposed Seed Rating: P

PEST RATING PROFILE

Initiating Event:

A. rudis has been rated as “A” on the CDFA Plant Pest Rating List after being detected in a rice field in California.

History & Status:

Jointvetches are tropical emergent aquatic or terrestrial perennial, to 2 m tall that bear typical pea type flowers and jointed legume seed pods. There are about 150 species of jointvetch in subtropical and tropical areas of the world. No species are native to the Western United States, but one species (A. rudis) has been introduced. Plants are typically annual in California. Infestations were restricted to rice fields in Colusa County, California. Heavy infestations can reduce rice harvest yields, and seed is difficult to remove from rice grains during the milling process. Rough jointvetch (A. rudis) has often been misidentified as Indian jointvetch (A. indica) or northern jointvetch (A. virginica) in the Southeastern U.S. All are weeds of rice. The most common detection of these plants is as seed contaminants, but seeds are difficult to diagnose to the species level. Only a few species of jointvetch are likely to find a pathway to establishment in California (e.g., A. rudis and A. indica). Nevertheless, as these species are important rice field and wetland invaders, and species are hard to distinguish via seed, the genus is treated as a whole for purposes of risk assessment.

Official Control: May be eradicated from its one known site in California.

California Distribution: In California, this plant is known only from a rice field in Colusa County.

California Interceptions: It has been sent to the CDFA Diagnostics Laboratory for identification and has been detected in imported seed samples.

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 the plants appeared in California and could, presumably, spread to similar habitats elsewhere in the state.

2) Known Pest Host Range: Evaluate the host range of the pest. Score: 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: Evaluate the natural and artificial dispersal potential of the pest. Score: 2

– 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). The plant produces via numerous seeds that seem to be able to spread as a contaminant in rice seed, as well as by other means such as water and water birds.

4) Economic Impact: Evaluate the likely economic impacts of the pest to California using the criteria below. Score: 3

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.

Risk is High (3) as the plant could lower crop yield in rice, could lower crop value, trigger more treatments, and, as it can form dense stands in wet soil or shallow water, interfere with water delivery.

5) Environmental Impact: 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. Significantly impacting cultural practices, home/urban gardening or ornamental plantings.

Score the pest for 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

Risk is high (3) as the plant can disrupt wetlands. As such it could suppress native species, including rare wetland species, such as California hibiscus (Hibiscus lasiocarpus var. occidentalis) and California red-legged frog (Rana draytonii). The plant is toxic to mammals. Its presence triggers more treatments to control this weed.

Consequences of Introduction to California for Jointvetches:

Add up the total score and include it here. (13)

– Low = 5-8 points
– Medium = 9-12 points
– High = 13-15 points

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: 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:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (13)

Uncertainty:

Although zigzag jointvetch was successfully eradicated in California, the behavior of zigzag jointvetch (Aeschynomene rudis) and Indian jointvetch (Aeschynomene indica) in other areas of the world demonstrates the genus’ weedy potential in California.

Conclusion and Rating Justification:

The genus contains bad weeds of wetlands and rice fields. An A rated is justified for the genus, as the potential harm is great from introduction of any of the weedy species.

References:

Carulli, J. P. 1988. Aeschynomene rudis Benth. (Fabaceae) in the United States. Bartonia 54:18-20.

 Consortium of California Herbaria (ucjeps.berkeley.edu/consortium/).

Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford.

Hrusa, F., B. Ertter, A. Sanders, G. Leppig, and E. Dean. 2002. Catalog of non-native vascular plants occurring spontaneously in California beyond those addressed in The Jepson Manual. Part I. Madroño 49: 61-98.

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.