Bio-weapon against zebra mussels to get another test

ALEXANDRIA, Minn. -- Another trial of a biological weapon against an invasive species threatening Minnesota's lakes is planned near Alexandria this summer.

Scientists from the New York State Museum documented zebra mussels suffocating native clam species in June 2013. (Submitted photo)

ALEXANDRIA, Minn. -- Another trial of a biological weapon against an invasive species threatening Minnesota’s lakes is planned near Alexandria this summer.

In 2012, a trial of Zequanox was conducted on Lake Carlos in Douglas County. The 2013 study planned for Little Lake Darling will determine how effective Zequanox can be at saving native clam species from zebra mussels.

Denise Mayer, director and senior research scientist with the New York State Museum’s Field Research Laboratory, described Zequanox as a natural product used to eliminate the threat of zebra mussels. Her lab developed Pseudomonas fluorescens strain CL145A, the active ingredient in Zequanox.

Scientific teams visited Douglas County and scoped out a prime location during a scuba dive expedition in June.

“Lake Darling had both clams and zebra mussels,” Mayer said. “Carlos had zebras but the clams were already dead.”


Mayer is working on a U.S. Environmental Protection Agency project in collaboration with the U.S. Geological Survey out of La Crosse, Wis., and in cooperation with the Minnesota Department of Natural Resources.

Jim Luoma, study director with the Geological Survey, said the test on Lake Darling is contingent on weather, but could begin as early as the end of July.

Zebra mussels have been suffocating clams, which kills a vital part of the ecosystem. Clams dig down into the sediment and provide oxygenation to water bodies. Mayer said native clam species in North America are endangered.

“Since zebra mussels have come into waters, they’ve become the biggest threat (to clams),” Mayer said.

Lake Darling trial
Last year’s trial removed mussels and lake water and treated the water separately from the rest of the lake.

This year’s trial involves quarantining off 5-foot square sections in Lake Darling where zebra mussels are prevalent. Plastic sheeting will be inserted into the lake in depths of up to 5 feet of water. Zequanox will be added to six of nine such control units.

Some people are wary of the next step in the process – removing the plastic walls separating the controlled environments from the rest of the lake water, thus releasing Zequanox into the local aquatic habitat.

Mayer attests that Zequanox is not active 24 hours after application.


In a letter to the Cowdry, Taylor, Stony and Union Lakes Association, Mayer wrote that the goal of this year’s trial is to demonstrate whether treatment with Zequanox will effectively remove zebra mussels from native clams to ensure the clams’ survival.

The lakes association is researching the use of Zequanox and consulting professionals before making its opinion public. Members were notified of the 2013 research project when their lakes were being considered.

“We have not taken a stand as an association at this point,” said Peggy Olson with the association.

Luoma said a lot of people are confused about Zequanox. “It’s a killed cell, it can’t be infectious,” Luoma said. “This product is safer than many things we consume.”

Luoma directed the 2012 study on Lake Carlos, that he called a success.

Naturally confusing
People hear the term biopesticide associated with Zequanox. Personal protection equipment is recommended when handling the bacteria in powder form. But is it dangerous?

“No more dangerous than dust,” said Sarahann Rackl, director of water technologies for Marrone Bio Innovations, the company that markets Zequanox. “Even when people are cleaning their yards in the fall, it’s recommended to wear a mask.”

EPA documents precaution that the product is hazardous to humans and domestic animals if inhaled.


Rackl said “harmful to humans and domestic animals if inhaled” is standard EPA language for all dry or potentially dust-forming products.

The EPA label for Zequanox also states that discharging effluent containing the product into lakes, streams, ponds, estuaries, oceans or other waters is an environmental hazard unless done in accordance with the requirements of a National Pollutant Discharge Elimination System permit.

Luoma said the group is working closely with the DNR and assures all proper permits are in place. Applications of Zequanox must be used under the supervision of Marrone Bio Innovations.

Mayer explained that unlike a chemical, Pseudomonas fluorescens is a naturally occurring bacteria. Zebra mussels eat the bacteria and are killed by a reaction that occurs after consuming the product.

Initially, Zequanox was developed as an environmentally friendly agent for power plants to use in cleaning zebra mussels from pipes as an alternative to bleach and or cancer-causing agents.

The strain of Pseudomonas fluorescens is a bacteria that occurs naturally in North America.

“It’s probably the most common species of bacteria in the world,” Mayer said. “In truth, a low percentage of bacteria are bad. We need bacteria.”

Mayer said toxicity trials have demonstrated safety to other fish and mussels at the highest concentration tested.


A materials safety data sheet from April 2013 lists Zequanox as nontoxic or practically nontoxic to mammalian and avian wildlife. Zebra and quagga mussels are affected by the product, while it poses a low toxicity to freshwater fish, native mollusks, insects, plants, crustaceans and other aquatic organisms.

People can swim in, eat fish from, irrigate crops with and even drink water that has been treated with Zequanox.

“It’s part of nature,” Rackle said. “We’re looking at nature to solve nature’s problem.”

Crystal Dey | Alexandria Echo Press

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