But a small beetle named Eustenopus villosus is beginning to tame yellow starthistle. Female beetles lay eggs in older buds and the larvae eat most of the maturing seeds before they can disperse. The beetle is the latest of five natural enemies imported by the Agricultural Research Service from the weed's homeland in Eurasia. The insects were released after years of safety and efficacy testing by several ARS scientists. Cooperators, such as University of Idaho researchers, monitor and redistribute insects from the initial release sites.
Biological control is viewed as the best long-term strategy for managing the weed.
Once it takes over, physical controls like cutting or pulling it can't keep up. Chemical control is too expensive for widespread use on rangeland and may be environmentally undesirable. Joe Balciunas, an entomologist at the Exotic and Invasive Weeds Research Unit in Albany, Calif., leads ARS' ongoing research effort to apply biological control to yellow starthistle. He's comparing the weed's seed production in the U.S. and in one of its native countries, Turkey, where yellow starthistle doesn't run amok. The goal is to reproduce here the conditions that keep the weed in check there.