Establishment of Rhinocyllus conicus (Coleoptera: Curculionidae) in Georgia for Control of Musk Thistle

Rhinocyllus conicus Froelich was introduced and successfully established at 21 sites in northern Georgia for biological control of musk thistle, Carduus nutans L. A total of 9,310 adults were released from 1990 through 1992. Releases of reproductively mature adults in the spring were much more successful than summer releases of teneral adults. Progeny were observed in all spring-release sites, and population increases occurred at most sites one and two years after release. Consumption of infested capitula by cattle reduced R. conicus numbers at some sites. After two years, weevils had dispersed up to 0.6 km from the initial release point. Transfer of R. conicus to new sites in Georgia will begin in 1993.