In war on milfoil, weevils enlisted as lesser of 2 evils

An amateur marine biologist thinks bugs could trump chemicals.

Mark Washa, an amateur marine biologist, rinsed and potted samples of Eurasian milfoil gathered from local lakes.

Photo: Glen Stubbe, Star Tribune

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The ice is long gone. The tanks are ready. Now, all Mark Washa needs are those darn elusive bugs.

Then he could at last launch his audacious plan to save Minnesota's lakes from invasive milfoil by proving that there is a healthier alternative to chemical herbicides -- the tiny weevil.

"In Minnesota, people don't have any other choice," he said on a recent Saturday, hunting for bugs in the rotting leaves on the edge of Lake Minnetonka, an icy rain dripping from his ears. "But people are clamoring for something else."

There are those who say that Washa, like Don Quixote, is tilting at windmills. Weevils, tiny insects that eat milfoil, have been tried before. They don't work, the skeptics say. Better to stick with more certain solutions, like chemicals, they say.

"It risks sending the message that there is an alternative control that is feasible, and I don't see it that way," said Dick Osgood, executive director of the Lake Minnetonka Association.

Still, Washa, 42, a "citizen scientist" with a long blond ponytail, a surfer's build and a day job as a lab technician, has an infectious idealism that has carried him a long way. In his spare time he's succeeded in recruiting help from university professors, local businesses and volunteers, and he's talked the Minnehaha Creek Watershed District into giving him a $5,000 grant for his weevil project.

"I always wanted to be a marine biologist," he said, lake water lapping the top of his rubber boots.

Hungry bug

The weevil is a long-snouted, yellow-striped aquatic insect rarely seen by human eyes. It's native to some Minnesota lakes, and its natural food is the native northern water milfoil. But it likes the invasive Eurasian variety even better, biologists say.

The adult female lays two to four eggs a day on the top of a plant, and when they hatch, the larvae eat their way down the stem, killing it as they go. Over the course of a summer they produce three or four generations of insects, and in the right circumstances they can do a lot of damage to a stand of milfoil.

That, in essence, is what University of Minnesota Prof. Ray Newman found through years of research funded with $1.3 million in state money. It worked great in tanks.

But in real life, weevils are food for the fishes -- especially little sunnies. "For every bug there is a fish that's eyeing him," said Steve McComas of Blue Water Science, who was hired by the watershed district to advise Washa.

But weevils can work. Sometimes. Newman says that lakes with few bluegills also tend to have less milfoil, a suggestive coincidence. But cold winters, water temperatures and the fluctuations in fish populations can all influence the number of bugs.

Washa points to the success of EnviroScience, an Ohio company that sells weevils for milfoil control in the United States and Canada. The company's website lists half-a-dozen success stories about milfoil control on lakes in Michigan, New York and Ontario. Multiple seasons of careful weevil stocking can bring milfoil infestations down to non-nuisance levels for the long term, the company says.

"A lot of times solutions have to come from the private sector," Washa said.

Local weevils

Washa's skeptics remain unconvinced.

Newman says weevil results have been uneven, and Osgood flat out says Washa's idea won't work. This summer he's leading a $400,000 herbicide program for Lake Minnetonka, and he says Washa is a distraction in the effort to protect the metro area's biggest lake.

The Minnesota Department of Natural Resources, which manages control of aquatic invasive species in the state, also blocked Washa at first. It would not allow him to buy weevils from EnviroScience.

Chip Welling, director of the DNR's invasives program, said EnviroScience grows and ships the bugs on milfoil plants. Bringing non-native bugs and yet another variety of invasive milfoil into the state is a really bad idea, Welling said. "What we have is plenty," he said.

But eventually the DNR said Washa could collect Minnesota bugs from Minnesota lakes and grow them in aquarium tanks on locally collected milfoil.

When he gets enough weevils, probably 300 to 500, Washa plans to install a fish barrier around a stand of milfoil in Christmas Lake, then set the bugs loose to do what they do best. If that works, the system could be replicated in many of the 264 lakes in Minnesota with invasive milfoil, he said.

But first he has to catch the bugs.

Herbicide chemistry

Washa started on his quest in 2008, when he and his father failed to catch fish at one of their favorite spots on Lake Minnetonka. His father wondered out loud if it was because of the milfoil herbicides, which were being used for the first time that year on the lake.

That sent Washa to Google.

Now, he's on the watershed district's citizen advisory council, and he drives to public meetings in a bright yellow pickup truck that doubles as his office. He knows the chemistry of all the herbicides and says they are bad for the lake, bad for the fish and wildlife.

"After I speak, people come up to me and say 'I feel the same way,'" he said. "That's what keeps me going. I'm bringing them out of the woodwork."

The herbicides used in Lake Minnetonka are approved by the Environmental Protection Agency. Osgood and Welling said that, used correctly, they are not known to harm fish or humans.

The biggest problem with herbicides is that they, well, kill the plants. Used properly, the herbicides should not have a big impact on native foliage, said Newman and Welling. But the problem with milfoil is that it grows up to the surface, where it accumulates in huge canopies that block sunlight, squeezing out native plants. When the milfoil goes, there's often nothing else left beneath it. In many lakes that leaves an opening for algae growth and another invasive -- curly-leaf pond weed. And the herbicides have to be re-applied every few years.

"It's an ongoing challenge to balance the benefit of control of milfoil with the risk of reducing all plants on a lake-wide basis," Welling said.

What about the bluegills?

Osgood says the herbicide program on Lake Minnetonka has been enormously successful. In 2009 the badly infested Grays Bay was declared "milfoil free." This summer, the plan calls for applications in five bays, funded mostly by property owners, he said.

"Milfoil free can be accomplished" lake-wide, he said. He scoffs at Washa's project.

"Even if it works, what are you going to do, kill all the bluegills?" he said.

Washa is now beginning to understand how daunting his project is. He and some of his volunteers have been searching for specimens in lakes where Newman has found weevils before. First, he looked where they spend the winter -- under the leaf litter and in the mud along the shore. But by now they are most likely in the water, so last week Washa donned his scuba gear and spent a cold afternoon hunting for the one-eighth inch bugs in the weeds.

McComas, his adviser, said a realistic goal for this summer will be to raise enough bugs in tanks to actually launch the project next year.

Sadly, Washa is not as good as a bluegill at catching weevils.

"It's tough," he said dejectedly last week after his cold afternoon in the water. "We found one, and got it in a jar. But it's not the right type."

Josephine Marcotty • 612-673-7394

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