Adult Psylliodes chalcomerus insect (Image courtesy Mark Volkovitsh, Zoological Institute, Russian Academy of Sciences. Not available in 300 dpi)

Larva of Psylliodes chalcomerus that tunneled into a starthistle stem. (Image courtesy Mark Volkovitsh, Zoological Institute, Russian Academy of Sciences. Not available in 300 dpi)

Flea Beetle Getting at Root of Invasive Weed Problem

Agricultural Research Service scientists are identifying the distinguishing traits of a flea beetle that researchers overseas believe is a useful enemy of the invasive weed called yellow starthistle.

Scientists at the Biotechnology and Biological Control Agency in Rome and the Russian Academy of Sciences' Zoological Institute in St. Petersburg, working with the ARS European Biological Control Laboratory in Montpellier, France, found that the insect, Psylliodes chalcomerus Illiger, seems to have an appetite for yellow starthistle's roots, stems and leaves. All previously known insect enemies of the weed attack its flowerheads.

However, only a specific population of P. chalcomerus was found to be effective.

It's vital that the insect's correct identity be verified, not only to assure that the right insect is used to control the weed, but also to determine if this beetle might constitute a new, previously unrecognized species. So the European scientists sent samples of it to insect identification specialists at the ARS Systematic Entomology Laboratory in Washington, D.C.

There, entomologist Alexander Konstantinov, a world expert on this group of beetles, is comparing the specimens with insects in the National Collection of the Smithsonian Institution, where his lab is located.

Yellow starthistle, Centaurea solstitialis, probably costs the nation's livestock and forage crop industries millions of dollars each year. It supplants valuable grazing areas and is toxic to horses, causing a fatal illness known as chewing disease.

Accidentally introduced into California during the mid-19th Century in alfalfa seed shipments, yellow starthistle can now be found in 28 states and most of southern Canada. It also causes economic distress in Chile, Australia and South Africa. Once established, it is spread mostly through human activity.

Some seeds of the host plants used in the European studies were obtained from the ARS Western Regional Research Center's Exotic Invasive Weeds Research Unit in Albany, Calif.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.