CASSIDA AZUREA FAB. (COLEOPTERA, CHRYSOMELIDAE) - HOST-SPECIFICITY AND ESTABLISHMENT IN CANADA AS A BIOLOGICAL-CONTROL AGENT AGAINST THE WEED SILENE VULGARIS (MOENCH) GARCKE

Cassida azurea Fab. (Coleoptera: Chrysomelidae) was studied as an agen t to control the weed bladder campion, Silene vulgaris (Moench) Garcke (Caryophyllaceae). To supplement previously published data on the bee tle's host range, additional no-choice experiments were conducted. Fir st-stage larvae were offered seven plant species related to bladder ca mpion. Only one adult male developed an Dianthus caryophyllus L. cv. C hina Doll and one female on Lychnis X haageana Lem. This female did no t produce eggs when it continued to feed on L. x haageana. In tests wi th adults, oogenesis occurred only if fed with bladder campion, and on e laid one egg while feeding on Gypsophila pacifica Kom. First-stage l arvae did not develop to adults on three native North American Silene spp., but two adults developed on three other native species. Based on results from these experiments and reports in the literature, it was concluded that C. azurea has a very narrow host range and permission f or field releases was granted in 1989. Releases were made in Manitoba, Saskatchewan, and Alberta from 1989 to 1993. Cassida azurea survived from 3 to 6 years and was considered established at 8 of the 18 releas e sites in the three provinces but has not yet increased to densities sufficient to reduce bladder campion populations.