Foreign Exploration and Evaluation of Biological Control Agents for Thistles and Tumbleweed
Exotic and Invasive Weeds Research
2011 Annual Report
1a.Objectives (from AD-416)
The objective of this cooperative research project is to discover prospective biological control agents of yellow starthistle, Scotch thistle, Russian thistle (tumbleweed) and other weeds of mutual interest in Europe, Asia and Africa, and to conduct experiments to evaluate the host plant specificity and potential efficacy of the more promising species.
1b.Approach (from AD-416)
Explorations will be conducted at different seasons to regions where the target plants are known to occur to collect arthropods and pathogens likely to be host-specific. Specimens will be identified by qualified taxonomists, and phylogenetic analysis of DNA will be done when appropriate. Prospective agents will be evaluated using host specificity experiments to determine if they feed, oviposit, or develop on representative nontarget plants that are likely to be at risk of attack. Further tests under laboratory or field conditions will be conducted when appropriate. Populations of promising agents will be sent to quarantine laboratories in the U.S. to conduct further tests on the most promising agents.
Exploration for new biological control agents of Russian thistle and Scotch thistle was conducted in Italy, Spain, and Turkey. The weevil Trichosirocalus briesei collected in Spain, was evaluated for host plant specificity in our quarantine laboratory. Results of choice experiments under confined conditions indicate preference for Scotch thistle, but possible risk to nontarget Cirsium (thistle) species. Two species of insects were received in our quarantine laboratory for host specificity evaluation: Lixus cardui for Scotch thistle and Lixus rosenschoeldi for Russian thistle. Planning, reporting and analysis were conducted by email and periodic meetings, and an onsite visit in June 2011.