ROSEAU RIVER WILDLIFE MANAGEMENT AREA, Minn. — The contrast told the story.
Part of the wall of cattails on the eastern edge of this massive wildlife management area had been sprayed by helicopter a few weeks earlier, with the goal of restoring wetland habitat for waterfowl and other wildlife; part of it hadn’t been treated.
The difference was striking.
Video courtesy of the Minnesota Department of Natural Resources
“This is really declaring war on it, to get up and do the aerial cattail spraying,” said Randy Prachar, manager of Roseau River WMA, pointing to the lighter-colored area that had been sprayed just a few weeks earlier. “Aerial spraying is the way to go, and with GPS, they’re pretty exact.”
As it has the past few years, the Minnesota Department of Natural Resources waged an aerial assault on hybrid cattails again this summer, using an Enforcement Division helicopter rigged with spraying equipment to hit the cattails with an aquatically approved version of a glyphosate-based herbicide.
Long a bane of wetland and wildlife managers, hybrid cattails are a cross between the native broadleaf cattail and the invasive narrowleaf cattail. As invasive species often are, hybrid and narrowleaf cattails are aggressive, choking out wetlands and overtaking the native broadleaf cattails or other desirable plants such as wild rice.
The resulting habitat isn’t much good for anything.
“It sort of crowds out everything else in there,” Prachar said. “The big thing, I think, for waterfowl management is it tends to crowd out your open space and that hodgepodge of open water and cover that’s your best habitat.”
Hybrid cattails also are tough to control, and managers historically have tried everything from burning to chopping, often with marginal results.
Flooding can drown out invasive cattails, but that doesn’t work at Roseau River WMA and many other wetland sites across Minnesota because they sit on floating bogs that rise and fall with the water level, Prachar said.
Following the guidelines
Despite the concerns people might have about using herbicides in a wetland setting, DNR staff are trained to use the chemical properly and “strictly follow” instructions and safety guidelines, said Ricky Lien, Wetland Habitat Team supervisor for the DNR in St. Paul.
The DNR treated 1,782 acres at 52 sites across the state this field season, which wrapped up in late August, and has sprayed more than 9,400 acres since implementing the helicopter spraying program, Lien said.
“There are no perfect methods to deal with the invasive hybrid cattails that are ruining wetlands across much of the state,” Lien said. “Aerial spraying done by highly trained staff who strictly follow label instructions is the best method we currently have of trying to make some sort of positive impact to restore wetlands that would otherwise have little to no value to wildlife.”
The helicopter sprayed about 200 acres at Roseau River in late July, Prachar said. Combined with similar efforts in previous years, the results are beginning to show. At least one site that was a wall of cattails a few years ago now is rich with wild rice, prized by ducks and humans alike.
It’s not a one-and-done effort, he said, and the aerial war on invasive cattails should be repeated in three to five years.
“If you aren’t willing to come back that second time, you should not even bother doing it the first time,” Prachar said. “You end up letting it get a toehold again if you only do it the first time, and it will recolonize. You don’t want to get it back like that again.”
Other agencies also wage aerial war on the cattails. Gregg Knutsen, manager of Rydell and Glacial Ridge national wildlife refuges in Polk County, said treatments tend to be very site-specific. Before becoming manager of Rydell and Glacial Ridge, Knutsen was a biologist at Agassiz National Wildlife Refuge northeast of Thief River Falls, which has an abundance of huge wetlands.
The refuges are part of the U.S. Fish and Wildlife Service’s National Wildlife Refuge System.
“There are lots of variables involved that determine how effective the treatment is and for how long we see a good habitat benefit,” Knutsen said. “We try to collect habitat condition data on the wetlands we treat, both before and after chemical application. Over the years, this has helped us learn which wetlands are good treatment candidates, and which aren’t.
“Unfortunately, in my opinion, there’s still a lot we simply don’t fully understand about invasive cattails.”
As part of the DNR’s spraying program, a DNR “roving crew” provides ground support for the helicopter. The crew, which usually consists of two or three people, brings trucks with fuel, water and herbicide to the work site and ensures there’s a mowed place for the helicopter to land so grass doesn’t clog the spraying equipment or exhaust port, both of which are at the bottom of the aircraft.
Without that on-site ground support, the helicopter would spend more time flying off to refill fuel and herbicide than it would spraying, said Donovan Pietruszewski, the DNR’s Roving Crews and Habitat Projects manager based in Thief River Falls.
“It's a really slick, well-rehearsed organization,” said Pietruszewski, who supervises each of the DNR’s four roving crews across the state and a fifth that was approved for funding during the last legislative session.
Pietruszewski also prioritizes the sites to be targeted for aerial spraying. Conditions have to be just right, with wind speeds of no more than 12 mph, he said. The helicopter flies 10 feet to 20 feet above the cattails at about 50 mph, treating an area that’s 45 feet wide.
Funding the program
Funding for the DNR’s aerial cattail assault comes from the Lessard Sams Outdoor Heritage Council, which oversees the pot of dedicated funding for wildlife habitat that’s part of the Clean Water, Land and Legacy Amendment, which Minnesota voters approved in November 2008. Spraying cattails by helicopter costs $35 to $45 an acre.
Having its own equipment and staff also gives the DNR the flexibility to work when and where it’s needed, while keeping costs in check, said Lien, the DNR’s Wetland Habitat Team supervisor.
“We can do enough of it to start making an impact and make some meaningful improvement” for wetlands and wildlife, Lien said.