Submitted to: Weed Science Society of California Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 31, 2008
Publication Date: N/A
Interpretive Summary: Russian thistle (tumbleweed) is an important alien weed that has invaded about 100 million acres in the western U.S. Tumbleweeds invade fallow fields, clog irrigation systems, are hazardous to automobile traffic, spread wildfires and harbor insect pests that transmit viruses to many vegetable crops. Two previously introduced biological control agents became established but are not providing sufficient control. We have evaluated several prospective new agents of this weed and have requested permission to introduce one of them. These new biological control agents should help reduce the populations of this weed to innocuous levels over extensive regions. Successful biological control would provide self-perpetuating long-term management of this weed, 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) in December 2004 requesting permission to release the blister mite (Aceria salsolae) to control Russian thistle (Salsola tragus) and its close relatives. Host specificity experiments conducted in the USDA quarantine laboratory in Albany, CA indicate that the mite will not attack native North American Chenopodiaceae species (goosefoot family) nor commercial species such as beats, spinach or quinoa. A seed-feeding and stem-boring caterpillar, Gymnancyla canella, is undergoing a third 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. Foreign exploration into new regions in Central Asia is revealing new prospective biological control agents to evaluate.