The musk thistle weevils offer the benefit of reducing musk thistle populations in areas where no control measures are being made and can contribute significantly to long-term control efforts in areas where musk thistle populations are high. Control of thistles by the weevils is a slow, but effective process. Flower Head Weevil Musk thistle flower head weevils overwinter as adults. In early spring, the adults emerge from overwintering sites and seek out musk thistle rosettes. Adults feed on leaves of the plants, but do little damage.
Females then mate and begin laying eggs when the plants start to bolt and bloom.
Eggs are deposited on the bracts of the flowers. Each female lays an average of 100 eggs during its lifetime. The eggs hatch in six to eight days. Adult musk thistle flower head weevil. Flower head weevil eggs covered with plant material.