ESTABLISHMENT OF RHINOCYLLUS-CONICUS FROELICH (COLEOPTERA, CURCULIONIDAE) IN NORTHWEST LOUISIANA

Adults of an imported biological control agent, Rhinocyllus conicus Fr oelich (Coleoptera: Curculionidae), were first released in Louisiana o n 19 May 1975 for control of musk thistle, Carduus mutans L. (Asterace ae). This release and a subsequent release in Louisiana on 17 June 197 5 were made in southern Red River Parish just south of Hanna, LA. Appr oximately 450-500 adult weevils were released on each date. On 16 July 1976, six sites were surveyed for Rhinocyllus conicus infested flower heads. Three sites were located in Red River Parish and one site each in Bossier, Caddo, and DeSoto Parishes. Flowerhead infestations ranged from 0% in Bossier Parish to 43% at one site in Red River Parish. Mea n weevil larvae per infested flowerhead ranged from 0 to 2.7. Flowerhe ad infestation was 12.5% at the 1975 release site. Infestations at two sites approximately 32 and 48 km from the 1975 release site indicate that the short-term dispersal capability of R. conicus may be greater than previously reported. On 20 May 1994, a 16-site survey was conduct ed in Northwest Louisiana. Five sites were located in Red River Parish , four sites in southern Caddo Parish, four sites in northern Caddo Pa rish, and three in Bossier Parish. Flowerhead infestation ranged from 0 to 84.2%, and mean weevil larvae per infested flowerhead ranged from 1.0 to 3.4. Sample Site 7 in the 1994 survey was nearest to the origi nal 1975 release point. Here, 65% of the flowerheads were infested wit h a mean of 2.2 weevil larvae per infested flowerhead.