Africa, temperate Asia and Eurasia (Balkan-Asia Minor, the Middle
East and south-central Europe) Mediterranean region of southern Europe
and northern Africa, especially Turkey
is an annual herbaceous plant. Plants are gray-green to blue-green, grow
from 6 in. to 5 ft. (15 cm to 15 dm) in height, and have deep taproots. Flowers
are bright yellow with sharp spines surrounding the base, giving the plant
a particularly menacing appearance and a painful response if touched. Stems
and leaves are covered with cottony wool. Basal leaves are 2 to 3 in. (6 – 7
cm.) long and deeply lobed . Upper leaves are short (0.5 to 1.0 in.; 1 to
2.5 cm) and narrow, with few lobes.
starthistle is a strong invader that has been found in nearly every county
in California and appears to be moving north and eastward. Some specialists
liken its invasion to that of leafy spurge in North Dakota and Montana. As
the plant infests an area, it chokes out the native plants, reducing biodiversity
and wildlife habitat and forage. Another concern associated with the plant
is “chewing disease” that develops in horses that have eaten
yellow starthistle. This disease affects horses’ nervous system and
is usually fatal. Yellow starthistle does best in areas with a summer drought.
It has been present in the Mid-West and eastern US for decades but has not
built up high densities and is not considered a threat to areas with summer
rainfall which includes most of the area east of the Rocky Mountains.
IN THE UNITED STATES
According to the USDA, yellow starthistle
occurs throughout the United States in forty-one states, with the exception
of Maine and Vermont, five southeastern states, and Alaska and Hawaii.
Yellow starthistle is most concentrated in California, where the plant
infests nearly 12 million acres of rangeland and wildland. It is also
reported to be invasive in natural areas of Idaho, Oregon, New Jersey,
Utah, and Washington, according to the Alien Plant Working Group and
five western national parks - Death Valley National Park, Glen Canyon
National Recreation Area, Redwood National Park, Sequoia and Kings Canyon
National Parks, and Yosemite National Park.
HABITAT IN THE UNITED STATES
starthistle is found typically in full sunlight and deep, well-drained soils,
where annual rainfall is between 10-60 inches, and is especially common in
disturbed areas such as roadsides.
was probably introduced into the United States through contaminated alfalfa
in the mid-1800’s.
BIOLOGY & SPREAD
of yellow starthistle is by seed and each seedhead can produce from 35 to
approximately 80 seeds. However, the seeds have no wind-dispersal mechanisms
so few seeds move more than two feet from the parent plant without assistance.
Therefore, animals and human influences, such as vehicles, contaminated crop
seed, hay or soil, and road maintenance, contribute greatly to the plant’s
rapid and long-distance spread.
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 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.
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.
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.
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.
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.
NOTICE: MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.
For more information on
the management of yellow starthistle, please contact:
DiTomaso, University of California-Davis, ditomaso at 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
Jil M. Swearingen, National
Park Service, Center for Urban Ecology, Washington,
Joe DiTomaso, Michael Pitcairn,
and Steve Schoenig
Jerry Asher, USDI Bureau of
Bossard, Carla C., John Randall,
and Marc C. Hashovsky. Invasive Plants of California’s Wildlands. University
of California Press, Berkeley. 2000.
DiTomaso, Joseph M., et al. The
UC Pest Management Guides – Yellow Star-thistle. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7402.html.
DiTomaso, Joseph M.. WeedRIC – Yellow
Star-thistle Information. http://wric.ucdavis.edu/yst/. 2001.
Royer, France and Richard Dickinson.
1999. Weeds of the Northern U.S. and Canada. University of Alberta Press
and Lone Pine Publishing.
Swearingen, J. 2009. WeedUS Database of Plants Invading Natural Areas in the United States: Yellow Starthistle (Centaurea solstitialis). http://www.invasive.org/weedus/subject.html?sub=4390.
USDA Agricultural Research Service
Germplasm Resources Information Network. 2004. http://www.ars-grin.gov
USDA, NRCS. 2009. The PLANTS Database (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
Whitson, Tom D. (et al.). 2000.
Weeds of the West. Western Weed Science Society of America.
Plant Conservation Alliance, Alien Plant Working Group.