Yellow starthistle : ecology and management on Pacific Northwest rangelands

Abstract

Yellow starthistle (Centaurea solstitialis L.) is a member of the knapweed (Centaurea L.) complex. It is poor forage for all livestock and causes “chewing disease,” a nervous disorder, in horses. Yellow starthistle infests millions of acres in California and the Pacific Northwest. Infestations range from scattered plants to dense stands associated with annual grasses. Yellow starthistle is native to the Mediterranean region of Europe and north Africa. By the early 1800s, it had arrived in California, probably in contaminated alfalfa seed. Yellow starthistle was first reported at Walla Walla, WA around the turn of the century and began spreading into perennial and annual grasslands throughout the Pacific Northwest in the 1920s.