Submitted to: California Invasive Plant Council
Publication Type: Proceedings
Publication Acceptance Date: 9/22/2007
Publication Date: 12/1/2007
Citation: Smith, L., Cristofaro, M., Tronci, C., Hayat, R. 2007. Evaluation of the rosette weevil, Ceratapion basicorne, a new biological control agent of yellow starthistle. California Invasive Plant Council. 11:11-14.
Technical Abstract: Yellow starthistle is an invasive alien weed from the Mediterranean region that infests about 20 million acres in the western U.S. This noxious weed displaces native plants, elevates the risk of wildfire, and diminishes the value of rangeland for grazing and recreational use. A classical biological control program, initiated in the late 1960s, resulted in establishment of six species of seedhead-feeding insects, but they have not reduced plant densities at most locations to acceptable levels. We have completed evaluation of a new prospective biological control agent to complement the previously introduced agents. Ceratapion basicorne is a weevil native to Eurasia whose larvae develop in root-crowns of yellow starthistle. We conducted a series of no-choice, choice and field experiments to measure the risk that this insect would pose to nontarget plants. Larval development occurred on only nine plant species, including safflower and bachelor's button, all of which are closely related alien species. Three years of field studies conducted in eastern Turkey demonstrated that the weevil does not damage safflower plants. The insect does not attack any native North American plants. We have requested permission to release this insect as a biological control agent of yellow starthistle.