|Smith, Lincoln - Link|
Submitted to: Biocontrol
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/28/2004
Publication Date: 6/1/2005
Citation: Uygur, S., Smith, L., Uygur, F.N., Cristofaro, M., Balciunas, J.K. 2005. Field assessment in land of origin of host specificity, infestation rate and impact of ceratapion basicorne (coleoptera: apionidae), a prospective biological control agent of yellow starthistle. Biocontrol. 50(3):525-541. Interpretive Summary: Yellow starthistle is one of the most important alien invasive weeds in the western United States, infesting 20 million acres. It interferes with land use such as grazing and recreation, displaces native species, and is toxic to horses. It is an alien plant that probably originated from the eastern Mediterranean. Six species of insects that attack the flower heads have been introduced for biological control, but they are not controlling the plant in most of its range. Therefore we are looking for new agents that attack other parts of the plant. This search has focussed on Turkey, which appears to be the center of origin of the weed. One of the most common insects attacking the rosettes in this region is the weevil, Ceratapion basicorne. We conducted studies to evaluate the host specificity, abundance and impact of this insect on yellow starthistle in Turkey. Our results indicate that this insect is probably more safe than was previously thought and that is worthy of more thorough evaluation as a prospective biological control agent.
Technical Abstract: The weevil, Ceratapion basicorne, which attacks rosettes of yellow starthistle, appears to be common in Central Turkey, attacking 25 to 100% of yellow starthistle plants. In a field experiment, weevils from the genus Ceratapion attacked 90% of yellow starthistle plants and 88% of milk thistle plants but not seven other plant species, including artichoke and safflower. We suspect that a different species of insect attacked milk thistle, but they emerged in the field before we could collect them for identification. Laboratory tests showed that C. basicorne does not oviposit in milk thistle. Ceratapion basicorne appears to be more host specific than was suggested by previous studies of a population in Italy. The insect is gregarious, and the number of larvae per plant was positively correlated to root diameter. We found up to 7 larvae attacking a single plant. The level of damage to individual plants was positively correlated to the proportion of plants attacked, indicating aggregation both among plants and within plants. Field data did not show any impact of the insect on plant size or number of flower heads, but germination rate of seeds produced by infested plants was 15% lower than for uninfested plants at two of three sites studied.