Progress in Yellow Starthistle Biological
By Kathryn Barry
February 22, 1999
A depressed patch of weeds in the Idaho wilderness is good news for land
managers. Thats because the depression provides some of the first visible
success by an imported six-legged natural enemy of yellow starthistle.
Known to scientists as Centaurea solsitialis, yellow starthistle is
among the top 10 worst weeds in several western states and covers tens of
millions of acres. It can kill horses that eat it, and other livestock will eat
only small portions of very young plants. The weed displaces other plants as it
spreads, and turns prime grazing land into worthless weed pastures.
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
weeds 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
cant 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. Hes comparing
the weed's seed production in the U.S. and in one of its native countries,
Turkey, where yellow starthistle doesnt run amok. The goal is to
reproduce here the conditions that keep the weed in check there.
A story about yellow starthistle research appears in the February issue of
the agencys Agricultural
Research magazine and on the web at:
The Agricultural Research Service is the chief scientific agency of the
U.S. Department of Agriculture.
Scientific contact: Joseph K. Balciunas, ARS Exotic and Invasive
Weeds Unit, Albany, Calif., phone (510) 559-5975, fax (510) 559-5963,