Host plant specificity and potential impact of Aceria salsolae (Acari: Eriophyidae), an agent proposed for biological control of Russian thistle (Salsola tragus)

Russian thistle (common tumbleweed), Salsola tragus (Chenopodiaceae), is an alien weed that is widespread in the western United States. A population of the eriophyid mite, Aceria salsolae (Acari: Eriophyidae), was collected in Greece and evaluated for host plant specificity as a prospective biological control agent. The mite usually does not form galls, but is a vagrant that usually inhabits the crevices of leaf and flower buds. Feeding damage causes meristematic tissue to die, which stunts the plant. The mite was able to multiply only on species in the Salsola section Kali subsection Kali, which includes the alien weeds Salsola collina, Salsola kali, and Salsola paulsenii. It did not damage or multiply on Salsola soda, which is in a different section, nor on Halogeton glomeratus, which is in the same tribe. The mite reduced the size of Russian thistle plants by 66% at 25 weeks post-infestation under artificial conditions. The results indicate that the mite poses negligible risk to nontarget native North American plants or economic plants, and it may substantially reduce the size of Russian thistle plants and their population density.