Assessing the biological control of yellow starthistle (Centaurea solstitialis L): prospective analysis of the impact of the rosette weevil (Ceratapion basicorne (Illiger))

Authors: GUTIERREZ, ANDREW PAUL - University Of California; PONTI, LUIGI - Enea Casaccia Research Center; CRISTOFARO, MASSIMO - Enea Casaccia Research Center; Smith, Lincoln; PITCAIRN, MICHAEL - California Department Of Food And Agriculture

Submitted to: Agricultural and Forest Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2016
Publication Date: 12/22/2016
Citation: Gutierrez, A., Ponti, L., Cristofaro, M., Smith, L., Pitcairn, M.J. 2016. Assessing the biological control of yellow starthistle (Centaurea solstitialis L): prospective analysis of the impact of the rosette weevil (Ceratapion basicorne (Illiger)). Agricultural and Forest Entomology. 19: 257–273. doi:10.1111/afe.12205.

Interpretive Summary: Yellow starthistle is an alien weed that has invaded about 20 million acres in the western U.S. and is especially abundant in Pacific western states. The spiny plant interferes with grazing livestock and outdoors recreation, it is fatally poisonous to horses, and it outcompetes desirable vegetation. Six species of insects have been introduced as classical biological control agents, but they are not providing sufficient control in many areas. Foreign exploration in the Mediterranean Basin and experimental studies indicate that the weevil, Ceratapion basicorne, could be an important biological control agent. We expanded an existing computer model to simulate the effect of this weevil on yellow starthistle populations to help predict its potential efficacy. The results suggest that the weevil would reduce densities of mature yellow starthistle plants in many areas of the western USA by 70-80 percent. Achieving successful biological control would reduce the use of herbicides and increase the profitability of rangeland managed for production of cattle and horses.

Technical Abstract: Yellow starthistle (Centaurea solstitialis) is an invasive noxious weed originating from the Mediterranean region that is now widely established in Chile, Australia, and western North America. It arrived in California as a contaminant in alfalfa seed in 1859 and by 2002 had infested over 19 million acres in the USA. Biological control using weevils and flies that attack the seed heads, and a foliar rust pathogen of the leaves has been ongoing in the western USA for more than three decades, but with limited success. Computer modeling and field research suggest that natural enemies that kill whole plants and or reduce the seed production of survivors would be the best candidates for successful biological control. The rosette weevil, Ceratapion basicorne, which attacks the root crown of immature plants, has been evaluated as a possible biological control agent. In this paper, we add the biology of the rosette weevil to the computer model simulating population dynamics of yellow starthistle and the seed head insects, and use it to examine its potential distribution and impact on the control of yellow starthistle in the Western USA. The results suggest that densities of mature YST plants in the western USA would be reduced in many areas 70-80 percent by the added action of C. basicorne.