Propagation of Cyphocleonus achates (Fahraeus) (Coleoptera: Curculionidae) for biological control of spotted knapweed: procedures and cost

Cyphocleonus achates (Fahraeus) is a root-feeding weevil introduced from Eurasia for biological control of spotted knapweed, Centaurea maculosa Lamarck, in Montana and other areas of the northwestern United States. Because C. achates is flightless and univoltine, distribution of the weevil throughout the vast infestations of spotted knapweed in Montana and the northwestern United States will be extremely slow. To hasten the distribution of this promising weevil, a propagation effort using field corrals was initiated at the Western Agricultural Research Center in Corvallis, Montana. Procedures for propagating the weevil in field corrals are described. The direct cost of rearing 1000 C. achates adults for field release was $1634, an average of $1.63 per insect. Labor comprised 83% of the total direct cost. The described field-corral approach is effective and the cost appropriate for providing C. achates for initial colonization in the western United States