Minnesota DNR biologist Dan Swanson told the Pelican Lake Conservation Club extreme vigilance is needed to stave off introducing zebra mussels into the lake.

"Once a lake is infected, there simply is no way to eliminate the problem," Swanson said. "They can be controlled, but never eliminated."

Swanson gave a talk and slideshow presentation about invasive species at the regular meeting of the Pelican Lake Conservation Club in Breezy Point on Wednesday, March 11.

But just controlling the zebra mussel is problematic. There have been some attempts to rid the pest from Minnesota lakes by draining them, an idea that was tried on Lake Zumbro. It didn't work.

Another treatment is the application of copper sulfate, which also failed to produce spectacular results where it has been tried. The bottom line is, when zebra mussels establish a foothold in a lake, they stay forever, and they multiply rapidly.

There have been at least two close calls on Pelican Lake. Swanson showed a picture of a dock infected with zebra mussels that was almost lowered into the lake. Fortunately, an alert citizen spotted the cluster on the dock before it was put in the water.

The zebra mussel is native to the Black and Caspian seas. They were most likely brought to the United States on ships crossing the Atlantic, and then crossing into the Great Lakes, including Lake Superior. From Lake Superior, the zebra mussel has found its way into other Minnesota waters. The organism is in at least four Minnesota lakes and the Mississippi River.

The zebra mussel has been identified in Ossawinnamakee Lake, a gravity dam lake just north of Pelican Lake, and which could potentially pass the zebra mussel into Pelican Lake during times of high water.

Swanson said local residents must be extremely vigilant about monitoring boats coming into the lake. Boats should be inspected before being put in. All boats should be drained and pressure washed. They also should be allowed to dry for at least three to five days before re-entering any body of water.

Anything else that goes into the water should be thoroughly inspected as well, from docks, to nets and fishing equipment. Bait harvesters are also a major potential source of infection. Bait harvesters need to monitor their equipment with great care.

Another invasive species that has already established a small foothold on Pelican Lake is curly-leaf pondweed. Curly-leaf was most likely brought to Minnesota from Germany, Swanson said. It was first identified in Minnesota in 1910, and now is in 740 known locations.

Curly-leaf does best in bay areas and can completely overtake the water, bad enough so a boat would not be able to move through it.

Although a number of pilot projects have been under way for about four years, Swanson said an effective way to battle curly-leaf is yet to be found. So far, mechanical harvesters have been used to physically remove the weed from some lakes, but since all of its turions, or winter buds, cannot be eliminated, the weed will simply grow back.

Another method of attack on curly-leaf is the application of various herbicides, but using chemicals in the delicate ecosystem of a lake can create other problems.

"We still don't know the answers," Swanson said about the problem of curly-leaf pondweed.

Pelican Lake was awarded a grant in 2008 to work on invasive species problems. The money will be used for watercraft inspections, professional seminars, posting warning signage and more.

Swanson had high praise for Pelican Lake Conservation Club members, saying they are doing the right thing by getting organized and proceeding with pilot projects to control invasive species.