Physiological host range of Ceratapion basicorne, a prospective biological control agent of Centaurea solstitialis (Asteraceae)

Ceratapion basicorne (Coleoptera: Apionidae) is a weevil native to Europe and western Asia that is being evaluated as a prospective classical biological control agent of Centaurea solstitialis (yellow starthistle) in the United States. Host plant specificity of the insect was evaluated in no-choice oviposition experiments. Feeding on leaf tissue by adult females was highly correlated to oviposition rate, both of which occurred primarily on plants in the tribe Cardueae, and especially those in the monophyletic subtribe Centaureinae. The highest rates of larval development occurred on Ce. solstitialis and Centaurea cyanus (bachelor’s button, garden cornflower), and there was significant development on Centaurea melitensis (Napa starthistle, tocalote), Cnicus benedictus (blessed thistle), Carthamus tinctorius (safflower), and Crupina vulgaris (common crupina). All the plants that supported some larval development are within a monophyletic clade within the Centaureinae. No native North American plants appear to be at risk of significant damage by this insect. Additional testing of safflower and bachelor’s button under choice conditions should complement these results to help determine the degree to which these plants are at risk.