Centaurea melitensis L. (Malta star-thistle )

 


Joseph M. DiTomaso, University of California - Davis,
Bugwood.org

 

 

 

Family: Asteraceae (Aster Family)

Synonym(s):

Duration: Annual, Biennial

Habit: Herb


Listed by:
Invasive Plant Atlas of the US: 1
Federal Noxious Weed: 0
TDA Noxious Weed: 0
TPWD Prohibited Exotic Species: 0

Description: DiTomaso (2001) states that C. melitensis is an erect winter annual with a spiny, yellow-flowered head that typically reaches 1 m tall. The stems are stiff and openly branched from near or above the base or sometimes not branched in very small plants. Stem leaves are alternate, and mostly linear or narrowly oblong to oblanceolate. Margins are smooth, toothed, or wavy, and leaf bases extend down the stems (decurrent) and give stems a winged appearance. Rosette leaves typically are withered by flowering time.

History:

Biology & Spread: DiTomaso (2001) reports that C. melitensis is insect-pollinated and reproduces by seed. Seed production is highly variable. Plants can produce 1-60 or more seeds per head and 1-100 heads or more per plant.

Ecological Threat: When star thistle infestations are high, native species can experience drought conditions even in years with normal rainfall (Gerlach et al., 1998, in DiTomaso, 2001).

US Habitat: Occurs in open, disturbed sites such as grasslands, rangeland, open woodlands, fields, pastures, roadsides, waste places and fields.

Distribution

US Nativity: Introduced to U.S.

Native Origin: Europe and North Africa

US States: AL, AZ, CA, GA, HI, IN, MA, MO, NJ, NM, NV, OR, PA, SC, TX, UT, WA, WI

Resembles/Alternatives: Resembles: Centaurea solstitialis

Management: Methods used to control yellow star thistle (Centaurea solstitialis) can be applied. A variety of methods are available for managing yellow starthistle, ranging from biological, chemical, and mechanical. For this reason, an integrated weed management plan, including tactics to prevent the spread of yellow starthistle outside of infested areas, is recommended. For example, when driving, walking, or moving livestock through infested areas, clothing, vehicles, and animals should be inspected and cleaned to remove any seeds before continuing on into uninfested areas.

Biological Control: Six biological control insects have been released in the United States for yellow starthistle control: Bangasternus orientalis, Eustenopus villosus, Urophora jaculata, Urophora sirunaseva, Larinus curtus, and Chaetorellia australis. Of these, five became established and three (B. orientalis, U. sirunaseva and E. villosus) are widespread. Also, the accidentally introduced fly, Chaetorellia succinea has a strong affinity to yellow starthistle and is found almost everywhere yellow starthistle occurs. All of these insects attack the seedhead of yellow starthistle, effectively limiting the number of seeds the plants are able to produce. Current research indicates that the insects have reduced seed yield by at least 50%. The rust fungus, Puccinia juncea var. solstitialis was released in California in 2003. It is too early to know if this rust will establish and eventually cause high mortality of yellow starthistle in the wild. Several more fungi and insects are currently being tested for introduction into the United States.

Chemical Control: Application of the systemic herbicides clopyralid or picloram between December and April seems to be the most effective. Application during the winter encourages the growth of other, more desirable, plants.

Mechanical Control: Mowing is effective during the early flowering stage or when most buds have produced spines. However, it is only successful when no leaves are present below the level of the cut.

Grazing: Sheep, goats, and cattle can graze on yellow starthistle in early spring, before the flower?s spines develop. Goats will also graze plants in the spiny or flowering stages. Grazing reduces biomass and seed production.

For more information on the management of yellow starthistle, please contact:

Joe DiTomaso, University of California-Davis, ditomaso@vegmail.ucdavis.edu Weed Records and Information Center (WeedRIC) - Yellow Starthistle http://wric.ucdavis.edu/yst

The University of California Pest Management Guides - Yellow Star-thistle http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7402.html

Encycloweedia - http://pi.cdfa.ca.gov/weedinfo/centaurea2.htm

USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS. MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.

Listing Source

Texas Department ofAgriculture Noxious Plant List
Texas Parks and Wildlife Department Prohibited Exotic Species
Invaders Program
Federal Noxious Weed
Union of Concerned Scientists
United States Forest Service Southern Research Station

Text References

Yellow Starthistle Information (DiTomaso, 2001), Global Invasive Species Database (http://www.issg.org/database)

Data Source

Last Updated: 2008-11-24 by HTG