Effects of Mowing or SprayingCarduus thoermerionRhinocyllus conicus

In 1988, mowing C.thoermerionce at the bud stage, twice at the bud stage, or once at early bloom of the primary inflorescences, eliminated emergence ofRhinocyllus 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 affectR. conicussurvival, whereas hexazinone reducedR. conicussurvival when applied at all growth stages.