Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/17/2005
Publication Date: 10/6/2005
Citation: Smith, L., Christofaro, M., Dolgovskaya, M.Y., Tronci, C., Hayat, R. 2005. Status of new agents for biological control of yellow starthistle and russian thistle. Meeting Proceedings of the California Invasive Plant Council Meeting, Oct. 6-8, 2005, Chico, CA. pp.
Interpretive Summary: Yellow starthistle and Russian thistle (tumbleweed) are important alien weeds that have invaded over 20 million acres in the western U.S. Yellow starthistle is a spiny plant that interferes with grazing livestock and outdoors recreation, it is fatally poisonous to horses, and it outcompetes desirable vegetation. Tumbleweeds invade fallow fields, clog irrigation systems, are hazardous to automobile traffic, spread wildfires and harbor important insect pests of many vegetable crops. Previously introduced biological control agents became established but are not providing sufficient control. We have evaluated several prospective new agents of these two weeds and have requested permission to introduce two of them. These new biological control agents should help reduce the populations of these two weeds to innocuous levels over extensive regions. Successful biological control will provide self-perpetuating long-term management of these weeds, reduce the need to apply pesticides, and increase the productivity and utility of millions of acres in the western U.S.
Technical Abstract: We submitted a petition to the APHIS Technical Advisory Group (TAG) requesting permission to release the weevil, Ceratapion basicorne, whose larvae develop inside the root crown of yellow starthistle (Centaurea solstitialis, YST) rosettes in the early spring. The insect has a wide geographic distribution in Eurasia and infests up to 100% of YST at sites in Turkey. Host specificity experiments conducted in the quarantine laboratory in Albany, CA and at field sites in eastern Turkey indicate that the insect will not attack native North American Cardueae species (thistles) nor commercial species such as artichoke and safflower. Psylliodes chalcomera is a flea beetle that attacks the stems of the plant just as it is beginning to bolt. A biotype of this species from southern Russia has proven to be highly host specific and pre-release evaluations are almost complete. A petition requesting permission to release the blister mite (Aceria salsolae) to control Russian thistle (Salsola tragus) and its close relatives was submitted to TAG in December 2004. A seed-feeding and stem-boring caterpillar, Gymnancyla canella, is undergoing a second year of host-specificity evaluation in Albany. Two interesting weevils (Anthypurinus biimpressus and Baris przewalskyi) have been discovered during foreign exploration in Tunisia and Kazakhstan.