A Breakthrough in Zebra Mussel Control? New Bacterial Combatant Shows Promise

Zebra mussels were first discovered in Lake Minnetonka back in 2010. Since then they have spread rapidly and are now found in most bays. With no natural predator, zebra mussels are virtually impossible to exterminate, and collateral damage to the ecosystem eliminates chemical treatment options in most cases.

But there may be a possible breakthrough in zebra mussel control.

A bacterial combatant called Zequanox has shown promising potential in eliminating zebra mussels, and researchers in Wisconsin are currently in the process of testing its effectiveness in an open freshwater setting. 

“There has been a lot of activity and interest in this,” Eric Evenson, Minnehaha Creek Watershed District Administrator, told U.S. Sen. Al Franken Thursday. “Right now we’re working cooperatively with the USGS out of LaCrosse, WI. Their researchers have an ongoing study on Lake Peppin and Carlos Lake looking at the potential of using Zequanox.”

Zequanox is not currently legal to use in lakes, only in pipes and private facilities. However, the company is working on registering with the federal government and gaining federal approval for use in public waterways.

Franken said during his Thursday morning visit to Lake Minnetonka that he would look into Zequanox and its current progress in securing federal approval for use in the nation’s lakes.

“Lake Minnetonka is on a list of lakes that we gave to the USGS as a possibility for a location for this research,” Evenson told him.

The Minnehaha Creek Watershed District has been monitoring the Lake Minnetonka’s zebra mussel infestation by taking water samples from throughout the lake and examining plankton populations—the primary diet of zebra mussels. All indications point to a growing zebra mussel infestation with no signs of slowing down.

Zebra mussels actually filter lake water and enhance its clarity, providing an even more conducive environment for milfoil to grow. Additionally, one of the shellfish’s favorite latching locations is the milfoil stalk.

Milfoil was first found in Lake Minnetonka in 1987 but was likely present for several years before its discovery. The invasive plant is believed to have been introduced to Lake Minnetonka by someone dumping an aquarium into the lake, although no confirmed source of the infestation has been confirmed.

Milfoil has flourished in Lake Minnetonka over the last 25 years, particularly in shallow bays and along shorelines.

The Lake Minnetonka Conservation District chemically treats milfoil groves on an annual basis and for more than a decade has used specialized floating harvesters to remove acres of the stalks each summer.

“It’s the only option in some places because chemical treatment doesn’t work,” Greenwood City Councilman Kelsey Page said.

Franken said during his Thursday visit to the area that a growing number of states are facing milfoil infestations and that the issue is garnering increased attention in the halls of the Senate.

An innovative biological technique to eradicate milfoil is currently being spearheaded by the Minnehaha Creek Watershed District that could put a significant dent in Lake Minnetonka’s milfoil patches.

Weevils are small beetles native to Lake Minnetonka and Minnesota that happen to enjoy feasting on milfoil. While their population in Lake Minnetonka is low, the MCWD plans to introduce dense populations of weevils this summer into several locations in and around Lake Minnetonka.