Lateral flower heads, produced over the course of the summer, may escape attack by this insect. Infested musk thistle flower heads. The rosette weevil, also called the crown weevil, occurs on musk thistle, bull thistle, and plumeless thistle. The weevils are not able to complete their life cycle in other thistles found in Alabama. They are about two-thirds the size of thistle head weevils and have a rough texture.
Adults emerge from summer resting places in the fall.
They lay eggs in the midrib of thistle leaves, and complete egg-laying in the spring. Adults, eggs, and larvae can all overwinter. An adult usually lays about 800 eggs. After 10 to 12 days, the eggs hatch, and the young weevils tunnel from the midrib toward the center growing point. It takes about a week for the larvae to make their way into the rosette.