In 1988, mowing C. thoermeri once at the bud stage, twice at the bud stage, or once at early bloom of the primary inflorescences, eliminated emergence of Rhinocyllus conicus, a weevil introduced as a biological control agent. Mowing at full bloom reduced weevil survival by 78.8%, whereas mowing at senescence had no effect. In 1989, mowing at full bloom or senescence did not affect weevil survival. Dicamba applied at the full bloom or senescence stage did not affect R. conicus survival, whereas hexazinone reduced R. conicus survival when applied at all growth stages.