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Watershed gets great results with treatment research

Flowering rush blanketed the Detroit Lakes beach in July of 2008 in this file photo taken near the swimming beach. BRIAN BASHAM/TRIBUNE

Greg Larson, one of the owners of the Subaru dealership in Detroit Lakes, gets a good feeling whenever he passes the city beach these days and doesn’t see reedy patches of flowering rush.

After all, his father, Winston Larson, was the driving force behind the mile-long city beach.

Winston Larson served as city engineer for some 30 years, and helped create the beach in 1967.

It would have broken his heart to see the beach marred by muck-producing flowering rush.

Engineering the mile-long beach “was a big project,” Greg Larson said. “He got one of the ‘Seven Wonders’ awards that year” from the Minnesota Society of Professional Engineers.

It may seem like one of the seven wonders of the world that the flowering rush has retreated so dramatically from the city beach and other parts of Detroit Lake, but it’s actually the result of hard work by a lot of people and a substantial financial investment by local government.

The results have been a research break-through on how best to treat flowering rush (an invasive species) and when best to apply the treatment to not harm native aquatic plants.

Now in its second year of “in-lake research,” the results have been impressive.

“We sure have reduced it, that’s for sure,” said Detroit Lakes Public Works Director Brad Green. “We’ve sure set it back, using the chemical applied in a timely manner — we’ve had nothing but compliments.”

The chemical used by researchers hired by the Pelican River Watershed District is Diquat, an EPA-approved and time-tested aquatic herbicide.

It is applied on the flowering rush underwater, about 6-8 inches above the lake bed. And it is applied during a specific timeframe in the spring before native underwater plants are growing, said Tera Guetter, administrator for the watershed district.

Tom and Barb Thomsen were so impressed with the results that they sent a letter of thanks to local officials.

“We can’t begin to tell you the difference … we have moving water again, the smell of stagnant water is gone and there is boat activity and enjoyment of the water again, especially in the ‘flats’ area on the west side of the lake,” they wrote.

The city beach is largely back to its old self again, said Barb Halbakken Fishburg, president of the Lake Detroiters Association.

“We’ve just noticed a huge influx of families using the beach this year,” she said.

That’s a big change from 2008-2010, when the flowering rush infestation made large segments of the city beach unappealing.

“I was very concerned about no activity on the beach because of the flowering rush,” Halbakken Fishburg said. “It was a seminal moment for our community.”

She credits Mary Beth Gilsdorf with writing a letter to the editor that inspired the 2008 Crush the Rush citizen campaign, in which volunteers hand-harvested flowering rush on sections of the city beach.

That led to popular support for a 1 percent sales tax on food and beverages sold at restaurants and bars, a city referendum that passed in 2010.

That in turn helped fund research on how to beat back the flowering rush invasion. The watershed district has also spent a lot of money on the problem.

Barb Halbakken Fishburg said things are going well on Detroit Lake — membership in the lake association has doubled from last year, and only a few lake homes are for sale, a far cry from recent years.

“People are just amazed at the better quality of lake life without the flowering rush,” Halbakken Fishburg said.

“The flats area (a shallow shelf on the west side of Big Detroit in the Shorewood Drive area) and the Long Bridge area was full of flowering rush — now it’s used by watercraft.”

The flowering rush has been treated in at least a dozen large stretches around Big and Little Detroit — and on lakes Sallie and Mellissa too.

Flowering rush has a root system, or rhizome, that looks like tubers, and the plant spreads via its root system, not through seeds, Guetter said.

It’s the root system that is attacked and shrunk using Diquat, as shown in core samples taken by researchers.

“Our researcher says if you want to reduce these plant populations, you have to keep up treatment — multiple treatments at least two times a year over several years,” she said.

Most flowering rush grows in water up to four feet deep, but it can grow in water up to 15 feet deep, which is one reason Guetter says “we’ll probably never completely eliminate it  — we can’t get at it.”

The DNR has also so far refused to allow treatment of flowering rush in areas where it is mixed with native bulrush, even though research has shown the bulrush will not be harmed, she said.

That reluctance to go after the rush everywhere is a frustration to Rick Michaelson, who lives on Lake Sallie.

“The treatment is working well when it’s applied … it’s working very well,” he said. “The problem is a couple acres are not being treated because the DNR doesn’t want the watershed to treat it.”

That includes one of the busiest traffic areas on the lake, near the fish hatchery, and he worries that all the traffic will spread the flowering rush around the lake.

“Even a pathway for boats would keep it from spreading,” he said.

Michaelson was an early supporter of the Crush the Rush effort.

“I just got involved because I was a concerned lakeshore owner in the Pelican River chain,” he said.

It’s important to be aggressive in going after flowering rush in lakes Melissa and Sallie to keep the infestation to a minimum, Guetter said.

The watershed district treated 172 acres in Detroit Lakes this year, up from 117 acres last year.

It treated 25 acres in Lake Sallie, up from 17 acres, and it treated 37 acres in Lake Melissa, up from 13 acres last year. Treatment in Deadshot Bay increased from 13 to 14 acres.

At the height of its research efforts the past few years, the watershed district was spending some $225,000 a year on flowering rush. The city has kicked in $25,000 a year the past several years to help out the cause.

Guetter hopes the district’s research team will finish up with a recommended treatment plan that will win the necessary DNR permits.

The goal is serious reduction of flowering rush, Guetter told the city council Tuesday. “And I think that’s something we ought to stick together on at permit time.”

The watershed district has come a long way in its approach to flowering rush, which first showed up in Deadshot Bay in the 1970s — from cutting it on the advice of specialists in the 1990s, which just made the problem worse, to treating the emerged section of the plant in the late 2000s, which didn’t work either.

“They finally got after it, the stuff they’re using now is working real well — I’m happy as heck,” said Greg Larson. “They finally got after it.”