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United States Department of Agriculture

Agricultural Research Service

Research Project: Foreign Exploration and Evaluation of Biological Control Agents for Thistles and Tumbleweed

Location: Exotic and Invasive Weeds Research

2012 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.

3.Progress Report:

This research focused on the collection and evaluation of new natural enemies of invasive weeds, and was linked with Objectives 2 and 3 of the parent research project. Over the full duration of this project, exploration for new biological control agents of Russian thistle and Scotch thistle was conducted in Italy, Bulgaria, and Turkey. The weevil Lixus rosenschoeldi collected in Sicily, was received in our quarantine to evaluate its host plant specificity in our quarantine laboratory. A field experiment was conducted in Igdir, Turkey, where we released Larinus filiformis, a prospective agent of yellow starthistle, and Larinus latus, a prospective agent of Scotch thistle to evaluate their potential risk to nontarget plant species. Results are incomplete because we are still rearing out adult insects, but so far Larinus filiforms has attacked only yellow star thistle, and Larinus latus has attacked only Scotch thistle.

Last Modified: 1/31/2015
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