A thistle bud or bloom should be included in the carton, and the lid should be sealed tightly to prevent escape. Plastic cartons should not be used because they allow moisture to build up, increasing mortality. Release weevils at the new site as soon as possible after collection to enable them to deposit most of their eggs at the release site rather than in the carton. Release weevils away from livestock Five to seven years may be required before weevil populations are high enough to provide significant thistle control. Back To Top Summary Musk thistle plants reproduce only by seed.
Mature plants die after seed is produced.
Herbicides are most effective if applied during spring or fall to musk thistles in the rosette stage. Rosette weevil larvae feed in the thistle crown and weaken or kill the plant. Flower head weevil larvae feed in the flower and reduce the number of seed produced. Mowing is most effective when done within two days after the terminal flower blooms. Good pasture management practices reduce establishment of musk thistles.