Field collection of musk thistle plants (Carduus nutans) harboring the biological control weevil, Trichosirocalus horridus.
Landscape view of rangeland near Collbran, Colorado, three years after efforts to eradicate musk thistle.
Close-up view of the stems of musk thistle (Carduus nutans) showing spiny flanges, with a flower bud in the background.