The invasive weed leafy spurge is now easier to locate, thanks to a new detection method developed by Agricultural Research Service (ARS) scientists and their cooperators.

ARS physical scientist Raymond Hunt developed and tested the method using NASA's advanced hyperspectral sensor, the Airborne Visible Infrared Imaging Spectrometer (AVIRIS). Hunt works at the ARS Hydrology and Remote Sensing Laboratory in Beltsville, Md.

Leafy spurge (Euphorbia esula L.) is a noxious invasive weed that causes more than $200 million in losses annually in the Great Plains and western United States. It displaces native vegetation and spreads both by seeds and by underground rhizomes. Shoots produce a milky-white sap that is toxic to cattle and horses. Infestations can be controlled by pesticides, goats or Aphthona flea beetles.

Hunt and his colleagues were among the first researchers to detect invasive weeds by using algorithms developed to detect minerals in rocks and soil by hyperspectral remote sensing. The method works by analyzing visible and near-infrared light from the sun, reflected off vegetation, and back to the AVIRIS sensor aboard NASA aircraft.

They used the algorithms to detect leafy spurge during its flowering stage, from June to July.

Different colors of light are reflected from the showy yellow-green flowers compared to the surrounding grass and other green vegetation. When tested against field data, the method proved to be 85 percent to 95 percent accurate -- much higher than other methods of remote sensing tested in the same area.

Working with USDA's Forest Service, Hunt is also refining the Weed Invasion Susceptibility Prediction (WISP) model to show areas where spurge and other invasive species are likely to grow.

When the model is ready for national use, Hunt would like to see it published on Google Earth or some other Internet site.