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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICAL CONTROL OF INVASIVE TERRESTRIAL AND RIPARIAN WEEDS IN THE FAR WESTERN U.S. REGION, WITH EMPHASIS ON THISTLES, BROOMS AND CAPE-IVY

Location: Exotic and Invasive Weeds Research

Title: Field release of a prospective biological control agent of weeds, Ceratapion basicorne, to evaluate potential risk to a nontarget crop

Authors
item Cristofaro, Massimo -
item Debiase, Alesio -
item Smith, Lincoln

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 2012
Publication Date: November 9, 2012
Citation: Cristofaro, M., Debiase, A., Smith, L. 2012. Field release of a prospective biological control agent of weeds, Ceratapion basicorne, to evaluate potential risk to a nontarget crop. Biological Control. 64:305-314.

Interpretive Summary: In order to be permitted for release, prospective biological control agents generally must be demonstrated to not pose risks to nontarget plants. Laboratory experiments evaluating host plant specificity are the most common method of evaluating such risk; however, they are constrained by limitations of space and number of replicates. Sometimes insects attack nontarget plants under laboratory conditions but not under natural conditions. Field experiments in the land of origin of the prospective agent can provide more realistic conditions, but the number of replicate plants is often still small. When a small risk is perceived for a very abundant plant, such as a crop, larger scale experiments are needed to improve confidence in the result. A field experiment was conducted in Italy to evaluate the risk posed to safflower by a prospective biological control agent of yellow starthistle (Centaurea solstitialis). No attack was observed in more than 1000 plants although the insect attacked yellow starthistle plants growing in the center of the safflower field. These results corroborate those of other experiments that indicate that this insect does not attack this crop under field conditions.

Technical Abstract: Ceratapion basicorne (Coleoptera: Apionidae) is a univoltine weevil native to Eurasia whose larvae develop in root-crowns of Centaurea solstitialis (yellow starthistle, Asteraceae). The weevil normally oviposits in the leaves of young yellow starthistle plants, and larvae develop inside the root crown and pupate inside the plant. We released adult C. basicorne in a field experiment in which two varieties of safflower were grown in solid blocks near a small number of yellow starthistle plants. Plants were harvested at the time of insect pupation, mature larvae and pupae were reared to adult stage on artificial diet, and small larvae or injured individuals were preserved in acetone for molecular genetic analysis. The weevil infested 51% of the yellow starthistle plants. No individuals of C. basicorne were reared from 1,021 safflower plants, indicating that the probability of attack is lower than 0.00098 (=1/1021). A different weevil, Ceratapion orientale, infested 1.5% of the safflower plants. These results corroborate two other published field studies in which C. basicorne was not reared from safflower. The combined results indicate a probability of attack less than 0.00059 (=1/1687). No amount of testing could reduce this probability to zero; however, the consistency of results from field experiments in three countries and the absence of any report of this insect being reared from safflower in the field support the conclusion that this insect poses no significant risk to safflower.

Last Modified: 4/18/2014
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