Distribution of Yellow Starthistle (Centaurea solstitialis) and Russian Knapweed (Centaurea repens)

Abstract

The world distributions of yellow starthistle (Centaurea solstitialis L. ♯ CENSO) and Russian knapweed (Centaurea repens L. ♯ CENRE) are mapped based on information from world regional floras. A survey of weed specialists and herbaria was made in the United States, and the extent of the infestations and economic importance of these weeds was determined for the 48 contiguous states. Yellow starthistle currently occurs in 209 counties in 23 states and has apparently increased in abundance since 1970. Russian knapweed was reported in 412 counties in 21 states and does not seem to be spreading. Both of these weedy plant species are of greater economic importance in the western United States than in the east.