Use of insects tested to control invasive riparian weed
Riparian ecosystems are particularly sensitive areas that can be threatened by invasive species and by the herbicide or pesticide options commonly used in uplands to control the invaders. Leafy spurge is one such invasive weed that has appeared along streams throughout much of the country. Forest Service scientists and collaborators set out to determine if the weed could be controlled by releasing a large number of flea beetles (Aphthona spp.), an easily collected natural enemy of leafy spurge, in infested riparian areas. They focused their efforts by releasing large, or inundative, numbers of biological control insects on weed populations found in small isolated patches along three streams in southwestern, central, and eastern Idaho.
They found that releasing 10 beetles per flowering stem had inconclusive, potentially small negative effects on leafy spurge biomass, crown, stem, and seedling density. But 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.
These findings enabled the Jordan Valley Cooperative Weed Management Area to receive a $25,000 grant to employ inundative beetle releases on leafy spurge in areas along tributaries of the Owyhee River in Idaho. The Salmon Challis National Forest is using this protocol to reduce leafy spurge populations on islands in the Salmon River. Forest Health Protection personnel in Ogden, Utah, used inundative releases to effectively control leafy spurge in regional riparian areas. Inundative releases of biocontrol insects also were used in the Hold the Line Program to deter the spread of leafy spurge into the Yellowstone and Teton ecosystems.
Forest Service Partners