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Officials tried a zebra mussel treatment in a Twin Cities lake, and it worked


A lake near Chanhassen has been treated for invasive zebra mussels. And authorities there say it looks like the treatment worked.

The Minnehaha Creek Watershed District reported that zebra mussels were found in Lake Minnewashta last month. The mussels were still pretty small and probably weren't reproducing yet.

So the 29 acre bay where the invasive species was found – known as "Little Minnie" – was treated with a copper product called EarthTecQZ. According to its website, EarthTecQZ is "one of the most practical approaches available at controlling the spread and infestation of this devastating species."

Here's how it works:

The EPA-registered product is added to the water. Then zebra mussels eat it and die within 96 hours.

The website says it's also non-toxic for "most fish and other non-target organisms."

Ten days after adding the product to the Minnewashta bay, it appears all of the mussels have been killed. Now district leaders just hope the waters will say zebra mussel-free. 

The lake will be monitored over the next few years to make sure the zebra mussels are all gone. 

“Information from homeowners is a key factor that will help us determine the long-term success of this treatment,” said Andrew Dickhart, the Carver County Aquatic Invasive Species program coordinator. “We encourage them to be vigilant as they prepare their boats and other water-related gear for winter.”

The MCWD says this Lake Minnewashta response is the largest known open water treatment for zebra mussels in the state.

MPR reports the treatment cost $30,000.

Right now, the Department of Natural Resources says zebra mussel treatments are still experimental. Some other treatments – successful and unsuccessful – have been tried in other lakes.

For information on some of those, click here.

Preventing zebra mussels

Zebra mussels attach to boats, lifts, plants and basically anything that goes in lakes.

The Department of Natural Resources says the invasive species can survive outside of water and spread from lake to lake if they aren't removed quickly.

Additionally, microscopic larvae can survive in water – like bait buckets, bilges, etc.

So to prevent the invasive species from spreading, you must clean weeds and other debris from from your boat, drain livewells and keep drain plugs out while traveling,. Also let lake equipment – like docks, lifts, swim rafts, etc. – dry out for at least 21 days before putting it into another body of water.

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