California Pest Rating
Brassica tournefortii Gouan. | Sahara mustard
Former Pest Rating: Q
CURRENT Pest Rating: C | Proposed Seed Rating: R
This plant has been rated as “Q” by CDFA botany staff.
History & Status:
The genus Brassica comprises about 40 species and many agricultural cultivars such as cabbage, mustard, bok choi, brussel sprouts, canola, broccoli, turnip, etc. Sahara mustard, as the name implies, is a species adapted to dry, sandy soils.
Sahara mustard forms a basal rosette like most mustards from which grows a highly branched inflorescence with hundreds of typical mustard 4-parted yellow flowers. The basal leaves generally have more than a dozen pairs of lobes or leaflets; this is more than is typical for most other Brassica spp. As the plant fruits, it dies. The dense tangle of stems and fruits breaks off at ground level and tumbles over the ground in windy situations, releasing seeds as it moves through the landscape. The seeds sometimes occur as a contaminant in agricultural seed lots and they are easily distinguishable from other mustard seeds.
Official Control: Some land managers control this plant, but where it is adapted it is generally too common to control it well.
California Distribution: Sahara mustard is known from at least 15 counties in California; most are in the southern California. It is very common in warm desert regions.
California Interceptions: Sahara mustard was first collected in California in the 1920s from the Coachilla Valley. From that region, it has spread widely to surrounding areas.
United States: Sahara mustard is known from California, Texas, New Mexico, Arizona, and Nevada in the United States.
International: Sahara mustard occurs in all of North Africa from Morocco through Egypt, in southern Europe, and through Western Asia. It is an introduced weed in Australia.
Consequences of Introduction:
1) Climate/Host Interaction: Risk is Mediium (2), as the plant is naturalized on roadsides in the desert and then moves into open desert from these areas. More recent finds in coastal California indicates that it may invade southern coastal areas as well.
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) as weeds do not require any one host, but grow wherever ecological conditions are favorable.
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 Medium (2). The plant produces a large number of seeds that spread along roads. It then spreads into the desert interior via the “tumbleweed” inflorescences. It is especially good at exploiting sandy soils.
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: The presence of this plant in the Anza Borrego desert impacts the spring wildflower tourist industry, as the plant outcompetes native wildflowers that form the basis of an important tourist industry. If it infests row crops or irrigated areas, it lowers crop value or crop yield.
Evaluate the economic impact of the pest to California using the criteria below.
Economic Impact: A, B, C, F
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: Risk is High (3) as the plant is able to dominate desert areas that are home to sensitive species such as desert tortoise, blunt-nosed leopard lizard, and many rare native plants.
Evaluate the environmental impact of the pest on California using the criteria below.
Environmental Impact: A, C, 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 could significantly impact 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 Sahara mustard: 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: Sahara mustard has been found in many counties in California, most commonly in the south. It has spread widely during the last 20 years in California. It receives a High (-3) 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.
The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (10)
Given that populations of Sahara mustard have exploded in the last 20 years, uncertainty is low. It only remains to be seen how well it can invade the Mediterranean coastal and central regions of California. The likelihood is that it has fully invaded the areas where it is best adapted and newer incursions will occur, but that they will prove to be limited.
Conclusion and Rating Justification:
Although Sahara mustard may be somewhat limited in its spread by its environmental preferences, it has shown itself quite invasive where it is adapted. Because it is so widespread, especially in the desert areas, it should be given a C rating.
Baldwin, B. G., D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, & D. H. Wilken, editors. 2012. The Jepson manual: vascular plants of California, second edition. University of California Press, Berkeley.
Berry, K. H., T. A. Gowan, D.M. Miller & M. L. Brooks. 2014. Models of Invasion and Establishment for African Mustard (Brassica tournefortii). Invasive Plant Science and Management 7: 599-616.
Bhagirath S. Chauhan, Gurjeet Gill, and Christopher Preston (2006) African mustard (Brassica tournefortii ) germination in southern Australia. Weed Science: September 2006, Vol. 54, No. 5, pp. 891-897.
Cal_IPC website. Sahara mustard (Brassica tournefortii) research. Accessed 12/17/2015: http://www.cal-ipc.org/ip/research/saharan/index.php
Consortium of California Herbaria: ucjeps.berkeley.edu/consortium/
Malusa, J., B. Halvorson, and D. Angell. 2003. Distribution of the exotic mustard Brassica tournefortii in the Mohawk Dunes and Mountains, Arizona. Desert Plants 19:31–36.
Sanders, A., & R. Minnich. 2000. Brassica tournefortii. in Bossard, C. C., J. M. Randall, and M. M. Hochovsky. Invasive Plants of California’s Wildlands. University of California Press, Berkeley, CA.
Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6650; plant.health[@]cdfa.ca.gov
Comment Period: CLOSED
45-day comment period: July 14, 2017 – August 28, 2017
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