Snail Medic | Pest Rating Proposals and Final Ratings

California Pest Rating for

Medicago scutellata (L.) Wilson; Snail Medic

Fabales: Fabaceae

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

PEST RATING PROFILE

Initiating Event:

This plant has been rated as “Q” by the CDFA Botany Laboratory.

History & Status:

Snail Medic is an annual herb with trifoliate leaves and comparatively large (6-7 mm) fruits that spiral (hence the common name), but lack prickles. The leaves are softly hairy and inconspicuously glandular. Flowers are borne on stems shorter than the petioles in groups of 2-3. In California, it appears in disturbed areas.

Official Control: None.

California Distribution: Snail Medic is known from Butte, Santa Clara, Monterey, and San Luis Obispo Counties.

California Interceptions: Vouchered specimens are known from Butte, Santa Clara, Monterey, and San Luis Obispo Counties.

United States: Snail Medic has only been found in North America in Delaware outside of California.

International: Snail Medic is native to Europe.

This risk Snail Medic would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: The plant has adapted to disturbed areas. It was first collected in 1924. Despite this early detection and its adaptation to ruderal habitats, it has not yet spread widely. It receives a Low (1) in this category.

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

– 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) 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. Score:

– 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: Snail Medic produces via numerous seeds that seem to be able to spread via gravity, and wildlife. Snail Medic receives a Medium (2) in this category.

Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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: Snail Medic may invade croplands as a weed in certain areas. Snail Medic receives a Low (1) in this category.

Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

5) Environmental Impact: Snail Medic is not likely to trigger new chemical treatments by ranchers and land managers, as it is much less invasive than its congener bur-clover (Medicago polymorpha). The plant is never dominant in CA. The plant is unlikely to disrupt natural communities. Snail Medic receives a Low (1) in this category.

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 impact cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– 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 Snail Medic: Low (8)

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: Snail Medic has been found in in 3 counties in California, but seems to be eradicated. It 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.

-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: Low (7)

Uncertainty:

Snail Medic has been in California a long time, but has spread very modestly. Although some weeds do take decades to show their true potential in an invaded area, it is not terribly likely to be true for snail medic. Therefore, uncertainty is medium to low.

Conclusion and Rating Justification:

Not a bad weed in CA and unlikely to become one. It may have a use as a small forage plant. A D rating is proposed.

References:

Baldwin, B. G., D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, and D. H. Wilken, editors. 2012. The Jepson manual: vascular plants of California, second edition. University of California Press, Berkeley.

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.

Florabase; Snail Medic: http://florabase.dpaw.wa.gov.au/browse/profile/2450

USDA Plants Database. Medicago scutellata. Accessed 6/12/2015:

http://plants.usda.gov/core/profile?symbol=MESC6

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.