Submitted to: Biocontrol Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/30/2012
Publication Date: 2/1/2012
Citation: Smith, L. 2012. Host plant oviposition preference of Ceratapion basicorne (Coleoptera:Apionidae), a potential biological control agent of yellow starthistle. Biocontrol Science and Technology. 22(4):407-418. Interpretive Summary: Yellow starthistle is one of the most important alien invasive weeds in the western United States, infesting 20 million acres of rangeland. It interferes with land use such as livestock grazing and human recreation, displaces native species, and is toxic to horses. It is an alien plant that probably originated from the eastern Mediterranean and was accidentally introduced to California over 130 years ago. This weed has been targeted for biological control because it appears to be controlled by natural enemies in its land of origin, but not in the United States. Six species of insects have been introduced that destroy seeds, but it appears that additional biological control agents are necessary. We are evaluating a weevil from Turkey, Ceratapion basicorne, that attacks the roots of immature plants in the spring before the plant can reproduce. Laboratory experiments that test host plant specificity by permitting the insect to choose among several plant species were conducted to complement laboratory no-choice and field experiments. The results conform to a general pattern of producing results intermediate between no-choice and field experiments, and support the hypothesis that the weevil will not damage any native plant species or crops. However, it may attack bachelor's button, which is an alien ornamental that is an invasive weed in some regions of the western USA.
Technical Abstract: 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. Choice oviposition experiments were conducted under laboratory conditions to help assess host plant specificity of the insect. Oviposition rates were highest on C. solstitialis (70% of eggs) and C. cyanus (bachelor's button, 20%), with low rates on C. melitensis (5%), Saussurea americana (3%), and Carthamus tinctorius (safflower, 1%). Adult feeding appears to be slightly less selective with 49% occurring on C. solstitialis, 23% on C. cyanus, 14% on S. americana, 10% on C. melitensis, and 3% on safflower. There was less oviposition relative to the amount of adult feeding on the nontarget species than on the target host plant, C. solstitialis. Nine safflower varieties were tested, and oviposition occurred on only five of them, at low rates. Adult feeding occurred on all safflower varieties tested, although at rates much lower than on yellow starthistle. Comparison of the results of the choice experiments to those of previously published no-choice experiments showed that oviposition on C. solstitialis did not differ whereas for the nontarget plant species, oviposition was much lower in choice than in no-choice experiments. Adult feeding showed a similar pattern, except that feeding on Ce. solstitialis was slightly lower in choice than in no-choice experiments, which may be because insects had to search for plants in the choice arena, but not in the no-choice experiments.