August 15, 2003
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 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 Builds Mock Village on Farmland to Measure Runoff Effects on Water Quality
With funding from the U.S. Environmental Protection Agency, the U.S. Department of Agriculture?s Agricultural Research Service is building a mock residential housing development on rolling farmland in Coshocton, Ohio, to find out what happens to streams and lakes as farmland is urbanized. EPA plans to use the results of this first, fully controlled study of water runoff to create a national program to trade runoff credits, just as air pollution credits are now traded.
Each year, ARS hydraulic engineer James Bonta and colleagues at the agency's North Appalachian Experimental Watershed in Coshocton will increase "development" until it covers 40 percent of each of the four watersheds they are working on. The watersheds range in size from one to seven acres.
Annual runoff from these watersheds has been monitored for many years, as has land use. This will provide long-term background data for comparison as "urbanization" proceeds.
Development replaces soil and vegetation that once soaked up rainwater and snowmelt with the impervious surfaces of roofs and roads. These changes increase the volume and speed of water runoff, increasing the risk of flooding, soil erosion and the transport of chemicals into waterways.
The scientists will build 3-foot-high "houses" covered with plastic. They will plow soil to simulate construction work, and they will plant lawns and use pesticides and fertilizers just as homeowners do.
Then they will measure the rate of increase in volume and peak flow rate of runoff and the increase in amounts of fertilizers, sediment and perhaps pesticides that end up in streams and lakes.
The researchers will also evaluate ways to reduce the runoff, such as installing roof gardens to trap rainwater and intermixing natural areas with homes and paved areas, to give water a chance to soak in before reaching waterways.
The EPA's Sustainable Environments Branch in Cincinnati, Ohio, is conducting this research jointly with ARS as a pilot program to find the most cost-effective ways to improve water quality.