Courtesy Photo/Image Phragmites, full growth

Photo by George Lauby The Platte River near Lexington, July 2008, after high water flattened phragmites that had been sprayed.

Courtesy Photo/Image A salt cedar

Invasive weeds that thrive in wetlands seriously harm wildlife habitat and water flows in the Platte River, but University of Nebraska-Lincoln researchers are working to combat them.

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Phragmites, also known as common reed, grow profusely along the river, particularly between Grand Island and North Platte, said Stevan Knezevic, integrated weed management specialist.

Mechanical, cultural, chemical and biological control methods are being used to fight phragmites.

"This is a bear," he said. "It's probably one of the most invasive species on this continent and there's no silver bullet" to get rid of it.

Farther west, weed specialist Bob Wilson of the Panhandle Research and Extension Center is leading efforts to control Russian olive and salt cedar along the river between the Wyoming state line and Lake McConaughey.

Knezevic is leading a three-year demonstration and research project into various control methods for common reed, including disking, mowing and chemicals. About 10 different experiments began last spring in four areas of the river between North Platte and Grand Island, where it is particularly invasive.

The experiments are being conducted on both public and private land with the permission and collaboration of landowners, the Nebraska Game and Parks Commission, the Rowe Sanctuary at Gibbon and the Nature Conservancy.

Since research has shown a single control method fails to provide long-term control of an invasive species, the experiments consist of blending various control methods at different times of the year to see which is most effective.

The work is being supported financially by the Riparian Vegetation Management Task Force. The task force, created by state legislation, includes representatives of wildlife management, local, state and federal entities.

The goal of the research, Knezevic said, is to find the right method to control non-native common reed that thrives in wetlands and can grow 10 to 15 feet tall.

"Once you have a stand, it's like a wall," he said.

Not only does the weed compete with native plant populations, it reduces wildlife habitat, creates a fire hazard, affects the water flow and depletes the water from the river.

"It's sucking up the Platte River when you have these large stands," he said.

Russian olive and salt cedar are shrub-like species that can grow more than 20 feet tall and choke out preferable native species and disturb wildlife habitat, Wilson said.

Wilson has found that the best control method is cutting down the shrubs and treating the stumps with herbicides. Two newer chemicals released by DuPont and Dow Chemical Co. have shown to be effective and more environmentally friendly than other herbicides, he said.

"They open up a whole new area of research," he said.

Wilson's research also includes determining a species to plant in place of the invasive weeds that will be resistant to herbicide residue.

Controlling the invasive weeds supports the Platte River Cooperative agreement, which requires Nebraska, Wyoming and Colorado to find ways to put more water back into the river, Wilson said. Because the weeds soak up so much water, getting rid of them will help keep water in the river, he said.

"By removing them you can liberate 33,000 acre feet of water back into the system," he said. Even after planting a new species after the weeds are gone, the net result will be a gain of 23,000 acre feet of water, he added.

Phragmites on the Platte River has been successfully sprayed. A season’s growth has been killed without harming surrounding plants. Work was done under the supervision of local officials, acting together as a task force. - Editor