Distribution of Carduus nutans, C. acanthoides, C. pycnocephalus, and C. crispus, in the United States

Abstract

A survey determined the extent and severity of the infestations of four species of Carduus thistles in the United States. In the mainland United States, 360 counties of 3068 have economically important infestations of musk thistle (Carduus nutans L.), the Appalachian and midwest regions harboring the greatest infestations. Plumeless thistle (Carduus acanthoides L.) and Italian thistle (Carduus pycnocephalus L.) are of economic importance, but have limited distribution. Welted thistle (Carduus crispus L.) is approaching pest status only in Virginia.