Yellow Starthistle Information
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Initial intro
Introduction and Spread
Initial introduction
The center of origin of yellow starthistle (Centaurea solstitialis L.) is believed to be Eurasia, where it is native to Balkan-Asia Minor, the Middle East and southcentral Europe (Maddox 1981). Its introduction in North America probably occurred sometime after 1849 as a seed contaminant in Chilean-grown alfalfa seed, also known as Chilean clover (Gerlach et al. 1998). A detailed review of the introduction and spread of yellow starthistle is described by Gerlach (1997a, b). Historical records indicate that alfalfa was first introduced to Chile from Spain in the 1600s and from Chile to California at the time of the gold rush. Despite its origin from Spain, the source of alfalfa in California before 1903 was only from Chile. After 1903, it was likely that alfalfa was also introduced from Spain, France, Italy, and perhaps Turkestan. In the early period of introduction farmers often reported that alfalfa seed was contaminated with weed seed, presumable this included yellow starthistle.
Spread and current distribution in California
It has been speculated that the spread of yellow starthistle in California occurred through a multiple step process (Gerlach 1997a, b). The first report of alfalfa cultivation was near Marysville, California, in 1851. Before the 1870's alfalfa was grown primarily along river levees near Sacramento, Marysville and San Francisco. These areas were characterized by deep, well-drained soils and easy access to drinking and irrigation water. Both animal and alfalfa forage were distributed only short distances. As a result, yellow starthistle infestations that accompanied alfalfa stands were fairly localized. From 1870 to about 1905 much of the surrounding areas previously consisting of dry-farmed wheat and barley fields were converted to both dryland and irrigated alfalfa fields. During this period, yellow starthistle established as dense local populations in these areas and along adjacent roadsides. The use of tractors and other equipment spread starthistle seed to other locations, including grain fields. Gerlach (1997a) indicates that yellow starthistle in California probably decreased between 1920 and 1940, most likely due to changes in crop production techniques and the widespread use of inorganic herbicides, such as sodium arsenite and sodium chlorate, along roadsides. However, around the 1930's or 1940's yellow starthistle began to invade the foothill grasslands. Thus, yellow starthistle now became a part of the grazing/weed system. By 1958, the weed was estimated to have invaded over 1 million acres of California (Maddox and Mayfield 1985), much of this in range or grasslands.
Since the 1960's three factors greatly contributed to its further spread, including extensive road building, increased suburban development, and an expansion in the ranching industry. These factors all contributed to the rapid and long-range dispersal of seed and the establishment of new satellite populations (Gerlach et al. 1998). Over the past 40 years, yellow starthistle has spread exponentially to infest rangelands, native grasslands, orchards, vineyards, pastures, roadsides, and wasteland areas. Infestations reached nearly 8 million acres by 1985 (Maddox and Mayfield 1985). Today, it is thought to have spread to over 15 million acres in California, and can be found in 56 of the 58 counties in California (Pitcairn et al. 1998b).
Spread and distribution the United States and the world
Introduction of yellow starthistle to other western states occurred in the 1870's and 1880's (Gerlach 1997a, Roche 1965). The first report outside of California was in Bingen, Washington (Sheley et al. 1999b). These first introductions likely occurred through contamination of alfalfa seed (Gerlach 1999a). During the 1920's, yellow starthistle expanded rapidly in grasslands within the Pacific Northwest states. By the mid-1980's it was estimated to occupy 280,000 acres in Idaho, 135,000 acres in Oregon, and 148,000 acres in Washington (Sheley et al. 1999b). In 1989, Callihan et al. estimated that yellow starthistle was expanding its range by 7,000 to 20,000 acres of rangeland per year in the west. By 1994, Sheley and Larson (1994c) estimated the rate of spread to be twice as rapid (15,000 to 50,000 acres per year).
When given a list of 15 rangeland weeds, a 1982 survey of 249 farmers and ranchers in Idaho indicated that yellow starthistle was the most important weed problem, with 53% of the respondents reporting it to be a serious problem. In a similar survey conducted in 1988, yellow starthistle also ranked as the number one problem, with 63% considering it serious (Carlson et al. 1985, 1990). In 1982, 23% of those surveyed indicated that yellow starthistle infested over 30% of their land. By 1988, 47% of the respondents estimated over 30% infestation.
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. Today yellow starthistle can be found in most of the temperate areas around the world (Maddox et al. 1985).
Mechanisms of spread
Human activities are the primary mechanism for long distance movement of yellow starthistle seed. Seed is transported in large amounts by road maintenance equipment and on the undercarriage of vehicles. The movement of contaminated hay and uncertified seed are also important long distance transportation mechanisms. Once at a new location, seed is transported in lesser amounts and over short to medium distances by animals and humans. The short, stiff, pappus bristles are covered with microscopic, stiff, appressed, hair-like barbs that can adhere to clothing, hair and fur. The pappus is not an effective long distance wind dispersal mechanism, as wind dispersal moves seeds only a few feet (Roché 1992).
