|
Yellow starthistle has become a huge problem in the
grasslands and foothills in several western states. It was probably first
introduced into California around the time of the Gold Rush in shipments of
alfalfa seed from Chile (Gerlach et al. 1998). It now occupies as much as 15
million acres in California (Pitcairn et al. 1998b) and is expanding rapidly
in Oregon, Idaho, and Washington. Today, yellow starthistle can be found in
23 of the 48 contiguous states, extending as far east as New York (Maddox et
al. 1985). It has also extended into Canada from British Columbia to Ontario.
Sheley and Larson (1994c) estimate the rate of spread to be 15,000 to 50,000
acres per year.
Yellow starthistle is an annual that germinates in the
fall and flowers the following May through September. It is a prolific seeder
and can produce up to 100,000 seeds per plant per year. Dense infestations
can produce 50-100 million seeds per acre (DiTomaso et al. 1999a, Maddox
1981). Seeds are too large to be effectively moved by wind, so human activity
is the primary means of dispersal (Roché 1992). Animals also transport the seeds. Some of the seeds are
covered with microscopic hair-like barbs that stick to fur, feathers, and
clothing.
The adverse effects from this invasive
plant are numerous. The economic impacts probably run into the millions of
dollars annually for livestock and forage crops alone (Callihan et al. 1982,
Roche and Roche 1988). Yellow starthistle has several one-inch spines below
each flower that effectively discourage livestock, wildlife, and
recreationists from using an area that is heavily infested (DiTomaso et al.
1998). It is toxic to horses, causing the fatal “chewing disease” (Cheeke and
Shull 1985) and it out-competes and replaces more valuable forage plants, reducing
wildlife habitat and rangeland values for grazing animals (Sheley and Larson
1994a). At least two endangered plants in Oregon are threatened by yellow
starthistle (Randall 1994, Yates, pers. obs. 2002). Recent studies have also
found that this weed depletes soil moisture reserves in annual and perennial
grasslands (DiTomaso et al. 2000, Dudley 2000, Borman et al. 1992).
Various
methods and techniques have been used and evaluated for control of yellow
starthistle. Mechanical methods include hand pulling, hoeing, weed whipping,
tillage, and mowing. Cultural methods include grazing management, prescribed
burning, and re-vegetation. Biocontrol methods include insects and pathogens
that will attack the plant. To date, six insects have been released and another
one is being studied. No pathogens have been released, but research is
currently underway. Chemical methods include the use of various herbicides to
kill the plant and/or discourage seed germination. For a thorough discussion
of the pros and cons of each control method, see http://wric.ucdavis.edu/yst/manage/management.html.
For more information on yellow
starthistle, see http://wric.ucdavis.edu/yst/yst.html
Literature Cited
Borman, M.M.,
D.E. Johnson, and W.C. Krueger. 1992. Soil moisture extraction by vegetation
in a Mediterranean/Maritime climatic regime. Agronomy Journal 84:897-904.
Callihan, R.H.,
R.L. Sheley, and D.C. Thill. 1982. Yellow starthistle: identification and
control. Current Info. Series No. 634, 4 pp. University of Idaho, College of
Agriculture.
Cheeke, P.R.
and L.R. Shull. 1985. Other plant toxins and poisonous plants. Ch. 11. Pages 358-392.
In, Natural Toxicants in Feeds and Poisonous Plants. The Avi Publ. Co.,
Westport, CT
DiTomaso, J.M.
1998. Biology and impact of yellow starthistle. Pg. 82-84, M.S. Hoddle, ed.
In, California Conference on Biological Control. Innovation in Biological
Control Research.
DiTomaso, J.M.,
G.B. Kyser, and M.S. Hastings. 1999a. Prescribed burning for control of
yellow starthistle (Centaurea
solstitialis) and enhanced native plant diversity. Weed Science 47:
233-242.
DiTomaso, J.M.
2000. Invasive weeds in rangelands: Species, impacts and management. Weed
Science 48:255-265.
Dudley, D.R.
2000. Wicked weed of the west. California Wild 53:32-35.
Gerlach, J.D.,
A. Dyer, and K.J. Rice. 1998. Grassland and foothill woodland ecosystems of
the Central Valley. Fremontia 26:39-43
Maddox, D.M. 1981.
Introduction, phenology, and density of yellow starthistle in coastal,
intercoastal, and central valley situations in California. ARR-W-20, pp.
1-33. USDA-ARS.
Maddox, D.M.,
A. Mayfield, and N.H. Poritz. 1985. Distribution of yellow starthistle (Centaurea solstitialis) and Russian
knapweed (Centaurea repens).
Weed Science 33(3):315-327.
Pitcairn, M.J., R.A.
O'Connell, and J.M. Gendron. 1998b. Yellow starthistle: survey of statewide
distribution. Pages 64-66. D.M. Woods, ed. In, Biological Control Program
Annual Summary, 1997. California Department of Food and Agriculture, Plant
Health and Pest Prevention Services, Sacramento, CA.
Randall, J.M.
1994. Weeds and the preservation of natural areas. Proc., California Weed
Science Society 46:143-154.
Roché, B.F.,
Jr. 1992. Achene dispersal in yellow starthistle (Centaurea solstitialis L.). Northwest Science 66:62-65.
Roché, C.T. and
B.F. Roché, Jr. 1988. Distribution and amount of four knapweed (Centaurea L.) species in eastern
Washington. Northwest Science 62:242-253.
Sheley, R.L.
and L.L. Larson. 1994a. Observation: Comparative live-history of cheatgrass
and yellow starthistle. Journal of Range Management 47:450-456.
Sheley, R.L.
and L.L. Larson. 1994c. Comparative growth and competition between cheatgrass
and yellow starthistle seedlings. Knapweed 8(2):3-4.
Yates, Gene. 2002.
Personal observation. Forest Botanist, Wallowa-Whitman National Forest,
|
