Leafy Spurge Costs Great Plains States $100 Million

Leafy spurge, an invasive plant from Eurasia, causes over $100 million in damage in the Great Plains states each year. Much of the economically measurable damage is to livestock producers, but of no less concern to ecologists is the damage that this plant causes to native plant communities.

In cooperation with the National Park Service and the Little Missouri National Grasslands, USGS scientist Diane Larson and graduate student Paul Rabie, both from the Northern Prairie Wildlife Research Center, are documenting the effects of leafy spurge in Theodore Roosevelt National Park, North Dakota. In addition, they are studying current control practices for leafy spurge, such as herbicides and biological control with flea beetles.

"The exciting thing about this work is that we're trying to get at information that goes beyond simple 'kill rates' of the weed with different control techniques," says Rabie. "Of course, we're interested in kill rates, but if we're going to try to repair the damage we also need to know how the whole ecosystem has been changed by the invasion of the non-native plant." One of the ways that leafy spurge, herbicides, or flea beetles may change the ecosystem is to alter the amount of nitrogen that is available to plants. Ecologists know that changes such as these can have profound effects on the ability of different plant species to thrive in an area.

Weeds typically require larger amounts of nitrogen than do the native prairie plants that evolved with limited nitrogen availability. "Basically, it's not enough to kill the weeds," says Rabie. "You want to be confident that once you've killed the weeds, you know what's going to come back and grow there next year."