Leafy spurge is an invasive weed that has appeared along streams throughout much of the country. Riparian ecosystems are particularly sensitive areas that can be threatened by nonnative invasive species. These areas also can be damaged by herbicides commonly used in uplands to control invasive plants. In a collaborative effort by the U.S. Forest Service, Bureau of Land Management, and Agricultural Research Service, researchers found an effective way to use an insect to control the weed. Flea beetles (Aphthona spp.) are a natural predator of leafy spurge in its native range in Europe and Asia. The researchers released huge numbers of the flea beetles that inundated patches of leafy spurge along three streams in southwestern, central, and eastern Idaho. They found that releasing 50 beetles per flowering stem reduced the biomass, crown, and stem density by 80 percent and seedling density by 60 percent, compared to untreated plots. Land managers are now applying this inundative method of biological control to other situations, such as to prevent leafy spurge outbreaks after wildfires, as well as exploring the methods effectiveness against other invasive weeds.