As referenced on the Minnesota Department of Agriculture's Biological Control webpage, biological control is "the use of natural enemies to control non-native pests."
Controlling Leafy Spurge With Flea Beetles in Clay County
Clay County, in cooperation with the U.S. Department of Agriculture, has been involved in a program since 1989 in which flea beetles are being used to control leafy spurge in the county. Since 1999, over 6 million flea beetles have been collected and released in Clay County with impressive results. Leafy spurge has been eradicated from several hundred acres of land in Clay County through this program.
The photos to the right were taken of flea beetles that had been collected in the county, prior to their release.