Officials managing the use of a biological agent to kill off zebra mussels in a Hennepin County lake are encouraged by the early results.
Christmas Lake, which is not far from Lake Minnetonka, is the first testing ground for a bacteria-based pesticide called Zequanox.
The Associated Press reports the Minnehaha Creek Watershed District found no zebra mussels survived in the confined test area, which measures 50 feet by 60 feet and includes the public boat landing in Shorewood.
Craig Dawson, who directs the District's aquatic invasive species program, tells KSTP that 11 days after treating the area, "It appears that we may have had 100% percent mortality. It sounds really good but we can't be sure."
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In parts of Christmas Lake outside the closed-off test area, divers did find about 25 zebra mussels, officials said.
Zequanox is a chemical-free pesticide, which was approved for open-water use by the Environmental Protection Agency this summer. It's producers say it is made with dead cells from a naturally occurring soil microbe, which kill the mussels that consume it.
The Watershed District is working with Minnesota's Department of Natural Resources on the experiment in driving out an invader who can threaten fish populations by upsetting the ecosystem in a lake or river. Zebra mussels can also damage water pipes and boat motors and leave a nasty slice on the foot of a swimmer.
The experimental use of Zequanox is coming to an end because the temperature of Christmas Lake is getting too cold for the pesticide to be effective.
But the Star Tribune reports the lake may continue to be a laboratory in the fight against the invasive species. The DNR is seeking federal approval to use potash in Christmas Lake, the newspaper says.
Potash has been used on an experimental basis in areas including Lake Winnipeg, with results that initially looked promising but proved less so by late summer.
The Star Tribune says managers of the Christmas Lake experiment plan to treat an area twice as large as the one used for Zequanox, provided they can gain approval from the state agriculture department and the Environmental Protection Agency.