Ward’s Weed | Carrichtera annua

California Pest Rating for
Ward’s Weed  |  Carrichtera annua
Family:  Brassicaceae 
Pest Rating: A  |  Proposed Seed Rating: R

Initiating Event:

Carrichtera annua was introduced in California in the early 2000’s and had no previous pest rating.  A pest rating proposal is required to determine a permanent rating for this pest.

History & Status:

Background: Carrichtera annua is an annual member of the mustard family (Brassicaceae) 1. It is commonly known as Ward’s weed. It is a small, upright to spreading, short-lived herbaceous plant which can grow 5-40 cm tall.  The stems, leaves and fruits are covered with bristly hairs3. Carrichtera annua can be easily distinguished from other members of the mustard family by its fruits and leaves. The fruits are globe-shaped with a curved oblong extension; the opposite leaves are bipinnately compound. The flower petals are pale yellowish and the sepals are hairy and lavender in color before the flower opens1.

Carrichtera annua is native to the Mediterranean region. It has been accidentally introduced to Australia and southern California. Carrichtera annua is a serious weed of semi-arid rangelands of Australia where the average annual rainfall is 250 mm – 350 mm. It is a common plant of dry open and disturbed sites of grassland and shrub land. Carrichtera annua is known to invade grassland areas, especially areas degraded by overgrazing, where it replaces pasture plants3.

Worldwide Distribution: Carrichtera annua is native to the Mediterranean region and western part of Asia.  It is reported in Algeria, Egypt, Libya, Morocco, Tunisia, Kuwait, Saudi Arabia, Cyprus, Egypt, Iran, Iraq, Israel, Jordan, Lebanon, Syria, Greece and Italy. It is widely naturalized in the inland regions of southern and central parts of Australia. It is also sparingly naturalized in Tasmania and parts of southern and central Queensland5.

Official Control: Carrichtera annua is not declared or considered noxious by any state government authorities7.

California Distribution:  Carrichtera annua currently is known from a limited area of San Diego County.

California Interceptions:  Only one PDR No 1559908 collected in San Diego on Feb 18, 2009 was found in the Pest and Damage Record Database by CDFA6. It was collected in 1979 in Salinas, Monterey County, CA (voucher: Johnson & Oliver s.n, CDFA).

The risk Carrichtera annua (Ward’s weed) would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: The plant has adapted to a wide area in its native range and is highly invasive in areas of Australia ecologically similar to California. Therefore Carrichtera annua receives a High (3) 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: Carrichtera annua do not require any one host, but grow wherever ecological conditions are favorable. It receives a High (3) 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: Carrichtera annua reproduces only by seed but it is capable of producing 30,000 seeds/mm2 annually2. These seeds are dispersed short distances by ants, foraging animals and human activity. They may be dispersed longer distances by vehicles, on larger animals and in contaminated agricultural produce. It receives a High (3) in this category.

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: Carrichtera annua can form dense stands becoming the dominant herbaceous plant which could lower the crop yield and its value. It displaces both native plants and other rangeland species and could negatively change normal cultural practices. It is unpalatable to livestock. It receives a High (3) in this category.

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

Economic Impact: A, B, D, 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: Carrichtera annua is likely to trigger new chemical treatments by ranchers and land managers. The plant can dominate grasslands and roadsides, excluding native plants and lowering biodiversity. Rare taxa that might be affected include species such as showy Indian clover (Trifolium amoenum), CA filaree (California macrophylla), San Diego ambrosia (Ambrosia pumila), vernal pool species such as Burke’s goldfields (Lasthenia burkei), CA tiger salamander (Ambystoma californiense), and grazers such as tule elk (Cervuscanadensis nannodes). The plant can disrupt natural communities. Carrichtera annua receives a High (3) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: A B, 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 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 Carrichtera annua (Wards weed): High (15)

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

6) Post Entry Distribution and Survey Information: Carrichtera annua has been reported only in San Diego County and seems likely restricted to this area. 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:

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: High (14)


Uncertainty is low, as the plant has spread widely in the Mediterranean and South Australia. Carrichtera annua is been in California about 15 years ago and it is localized in a limited area.

Conclusion and Rating Justification:

An A” rating is recommended, as the plant is invasive, but not yet widespread. There is still the chance to eradicate this plant from California.

  1. Jessie Vinje, 2008.  Center for Natural Lands Management. Cal-IPC News   page -9.   Accessed January 03, 2017 http://www.cal-ipc.org/resources/news/pdf/Cal-IPC_News_Winter08.pdf
  1. Julia Cooke, Dr.Julian Ash & Dr. Richard Groves. The Ecology of Ward’s weed. Australian National University. Accessed January 03, 2017 https://www.ecolsoc.org.au/files/pages/The%20Ecology%20of%20Ward’s%20Weed.pdf
  1. Impact Assessment – Wards weed (Carrichtera annua) in Victoria. State Govt. Assessment page.   Accessed January 03, 2017  http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/impact_wards_weed
  1. Special edition of Environmental Weeds of Australia for Biosecurity Queensland.  Accessed January 03, 2017 https://keyserver.lucidcentral.org/weeds/data/media/Html/carrichtera_annua.htm
  1. S. National Plant Germplasm System Accessed January 03, 2017. https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?id=310895
  1. Pest and Damage Record Database, California Department of Food and Agriculture, Plant Health and Pest Prevention Services. http://phpps.cdfa.ca.gov/user/frmLogon2.asp

USDA Phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD). Accessed January 03, 2017 https://pcit.aphis.usda.gov/pcit/ 

Responsible Party:

Javaid Iqbal, California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6695; plant.health[@]cdfa.ca.gov.

Pest Rating: A  |  Proposed Seed Rating: R

Posted by ls