Establishment in Missouri ofRhinocyllus conicusfor the Biological Control of Musk Thistle(Carduus nutans)

Abstract
A weevil,(Rhinocyllus conicusFroelich) was introduced into Missouri in 1975 to aid in reducing populations of musk thistle,(Carduus nutansL.). The weevil was recovered in 1976 from as far as 3.2 km from the release site and 4.8 km in 1977. Infestation levels of flower heads at the release site ranged from 46 to 90%. Native parasites(Bracon mellitorSay) and [Aliolus curculionis(Fitch)] were reared from weevil larvae.