As an Army National Guard helicopter pilot, Brad Maas has flown in Iraq and across Minnesota. Now flying for the Department of Natural Resources, he regularly conducts aerial moose and deer surveys and fish stockings.

But the pinpoint positioning required when Maas flies his aircraft low and slow, attempting to eradicate hybrid cattails, is unique among his many varied missions.

"It's an honor to be part of the crew trying to make these wetlands better for ducks and other wildlife," Maas said.

On Saturday, when Minnesota's 2020 duck season debuts, waterfowlers statewide will scan the skies for mallards, blue-winged teal and other winged quarry that have been in relatively short supply in recent decades.

Habitat loss that began with white settlement and accelerated last century because of intensifying agriculture and urban development is the primary reason.

Complicating Minnesota's duck dilemma, many of the state's remaining shallow lakes and wetlands are severely degraded. Some are infested with carp, which muddy the water, inhibiting aquatic plant growth. Others — like those seen through the windshield of Maas' helicopter over four weeks this summer — are choked with hybrid cattails.

"A lot of our wetlands are biological deserts because they get infested with hybrid cattails, which can take over entire wetlands, making them no good for waterfowl or anything else," said Ricky Lien, DNR wetland habitat team supervisor.

A cross of native broad-leaf cattails and invasive narrow-leaf cattails, hybrid cattails can aggressively outcompete other aquatic plants. In some instances, so little open water remains ducks can't find places to land.

Wildlife managers in Minnesota and other states have tried burning the invasive plants, mowing them and driving across ice-covered wetlands in winter to, in effect, decapitate them.

Few efforts have proved successful, except on very small wetlands.

"Spraying with a DNR helicopter was an idea that originally came from our enforcement division," Lien said. "They said a spraying boom could be attached to one of their helicopters to apply a herbicide to kill the hybrid cattails."

Money would be needed, and four years ago Lien and DNR wildlife prairie team leader Greg Hoch appealed to the Lessard-Sams Outdoor Heritage Council for $60,000 to purchase the spraying attachment and a smaller amount to outfit a DNR helicopter with specialized avionics that allow Maas to fly precisely over the targeted cattails.

When the funds were approved, a system involving about 60 wildlife managers statewide was developed to choose infested wetlands for treatment. Selected wetlands typically are large and located near similarly infested waters, so staffing and other costs can be minimized.

Coordination with the DNR's four (soon to be five) roving habitat crews is critical to the operation. Usually staffed with eight people and outfitted with gear ranging from skid steers to chain saws and tractors, the crews are stationed throughout the state and are charged with conducting prescribed burns and other habitat-enhancing projects.

Like the spraying work, which costs about $120,000 a year, funding for the roving habitat crews is provided by a $4.5 million annual Legacy Act grant recommended by the Lessard-Sams council.

Donovan Pietruszewski is the DNR's wildlife roving crews and habitat project manager, stationed in Thief River Falls. A former area wildlife manager, he oversees the habitat crews, including their support for the cattail spraying operation.

"Our goal is to make the spraying program effective, efficient and safe," Pietruszewski said. "Our crews have their helicopter-support work down to a science. They mow remote landing areas for the helicopter, bring the herbicide solution to the site and refill the sprayer's tanks."

Pietruszewski winnows the list of sites to be treated from submissions made by the area wildlife managers. Site boundaries and buffer areas are digitized by the managers to avoid herbicide "drift" outside of targeted areas.

"Then I convert the managers' digitized files to files compatible with the helicopter's avionics," Pietruszewski said. "It works using GPS coordinates. It's the same equipment used by crop dusters."

At altitudes ranging from 10 to 20 feet, Maas flies an Enstrom helicopter about 50 miles per hour while treating swaths 45 feet wide. When he reaches a site boundary, the aircraft's glyphosate-dispensing pumps shut off, and Maas turns his chopper for another pass.

Flights are scheduled only when wind speeds are 12 miles an hour or less.

"I might do two or three different sites in a day," Maas said. "I really enjoy it, and I think the spraying is improving our wetlands."

About 9,400 acres have been treated in the past four years. Depending on water depth and especially on whether affected plants are deeply rooted or instead are part of large floating "mats," their response might be immediate or delayed.

"We see a range of reactions," Lien said. "Some break down right away. Where there are dense stands of cattails, they might hold up a couple of years. We might have to repeat the spraying some years later. But in most cases, within a year or so, we see dead patches of cattails, along with open water and the emergence of healthy types of native vegetation."

Using chemicals on the state's lands or waters isn't preferred, Lien said. But with hybrid cattails, there are few options.

"We're very fortunate to have great people working on the spraying effort," Lien said. "Donovan and his crews are really good at what they do, and Brad, our pilot, is an enthusiastic supporter of the operation.

"If we want more ducks, we need more habitat."