It is best known as a controversial agent of biological pest control which has been used against noxious thistles in the genera Carduus, Cirsium, Onopordum, and Silybum.

As it grows it deposits frass and chewed plant tissue on the walls of its chamber, producing a rigid protective shell in which it will pupate.

Damage to the plant occurs mainly from larval destruction of the flower head, which prevents seed production.

Some larvae tunnel through the upper stem instead of chambering in a flower head; this can also be destructive to the plant.

However, the weevil will also readily attack native thistles of genus Cirsium,[1] in some cases contributing to population decline.