Title: Ecology and management of yellow starthistle (Centaurea solstitialis L.)
Abstract: Yellow starthistle is one of the more invasive weeds of the Pacific Northwest. A report from 2003 estimated that yellow starthistle infested nearly 15 million acres in 17 western states, with the majority of acres (12 million) being in California. In Montana it is currently the only Priority 1A listed noxious weed, meaning established populations are not in the state, and management criteria include education, prevention, and eradication when populations are found. Since 1958, 18 populations have been reported and controlled in Montana. Native to the Mediterranean region of Europe, yellow starthistle is a winter annual in the Asteraceae family. Seeds germinate in the fall and plants overwinter as seedlings. Seedlings transition into rosettes in early spring. Plants bolt and form spiny flowers (see Figure 1) in summer and may continue flowering until frost. Seeds set and disperse in late summer and early fall. Populations of yellow starthistle form dense stands on rangelands, pastures, roadsides, and wastelands where they displace plant native communities affecting critical wildlife habitat, accelerate soil erosion, and reduce forage for livestock and wildlife. Yellow starthistle causes chewing disease in horses which is typically fatal. Prevention, early detection and rapid response to eradicate new populations are the management priorities for Montana. New populations should be reported to county Extension agents or weed coordinators. Control options will include hand pulling to remove plants with seeds and herbicide applications. Consult your county Extension agent or weed coordinator for the best herbicide options for your area. [Jim Jacobs, Bozeman, Jane Mangold, Bozeman, Hilary Parkinson, Melissa Graves (2011). ExtensionEcology and management of yellow starthistle (Centaurea solstitialis L.). Invasive Species Technical Note No. MT-32 April 2011]. [Photo caption: Yellow starthistle growing along Interstate 90 in Gallatin County, Montana. Photo by Mike Jones, Gallatin County Weed District.]
