Purple loosestrife biocontrol underwayEach summer, Upper St. Croix Lake transforms into a sea of color in the shallow waters at the north and south ends of the lake. Tall stalks of purple or deep pink flowers dominate the other aquatic flora, and even though the flowers look pretty, they are an unwelcome sight for members of the Upper St. Croix Lake Association.
By: Emily Kram, Superior Telegram
Each summer, Upper St. Croix Lake transforms into a sea of color in the shallow waters at the north and south ends of the lake. Tall stalks of purple or deep pink flowers dominate the other aquatic flora, and even though the flowers look pretty, they are an unwelcome sight for members of the Upper St. Croix Lake Association.
For them, purple loosestrife is the enemy.
Lynne Nason, a member of the organization, was scouring the ditches near Solon Springs Wednesday with Lynn Zimek of the Gordon-St. Croix Flowage Association. Dressed in rubber boots or waders and armed with shovels, the duo sloshed through the water and mud, looking for the early shoots of purple loosestrife. The plants will not flower until late June or July, but the lake association has much work to do before that happens. The group will be raising beetles.
Two beetles of the genus Galerucella are used as a biocontrol for purple loosestrife. The insects feed only on purple loosestrife and have been found effective in containing the plant.
“You can see where the beetles are because the leafs get what we call ‘lacy,’” Zimek said.
The Upper St. Croix Lake Association group has a permit from the Department of Natural Resources to collect and raise purple loosestrife for the purpose of feeding the beetles. Once the plants are gathered, they are divided into buckets and put in a series of kiddie pools to simulate a swamp environment. The purple loosestrife is then placed inside an enclosure and allowed to grow before the beetles are collected and placed inside.
“This will be the third year we’ve used the cage,” Nason said. “I think it’s the sixth year overall (we’ve released beetles).”
The mesh-covered enclosure is set up outside the Solon Springs Mercantile. Peter Nason, Jim Heim and John Munsell worked to construct the cage while Lynne Nason and Zimek searched for plants.
In June, members of the lake association will travel to a marsh near the Northern Great Lakes Visitor Center in Ashland to gather the Galerucella beetles. There is no charge to collect them, but Nason said when the project was beginning years ago on the east cost, the insects cost $1 apiece.
As the beetles feed on the purple loosestrife they lay eggs. Near the end of July, thousands of offspring will be ready to relocate to the plants around Solon Springs.
Last year, the Upper St. Croix Lake Association did not raise beetles, but it has been monitoring the level of purple loosestrife around the lake. Lynne Nason, said the beetles have already had an impact.
“We can definitely tell,” she said. “And we can definitely tell that in the lake, the beetles don’t winter over.”
Because the beetles don’t reemerge near the lake in the summer as they do elsewhere, the lake association must reintroduce them each year to effectively combat the purple loosestrife.
Another key to winning the battle against the invasive plant is education.
As Nason walked through the ditch looking for purple loosestrife, Gene Lietha stepped away from working in his vegetable garden to ask was she was looking for. Nason described the purple flowers to Lietha and he was familiar with them, though he hadn’t known they were invasive.
“I thought they looked so pretty I dug one out and put it in my garden,” Lietha said.
Nason explained how the flower spreads and crowds out native plants, as it has in areas of Upper St. Croix Lake. Just one purple loosestrife plant can produce enough seeds to create 100 more.
“Well, I learned something new,” Lietha said.
Nason moved on to search the rest of the ditch for more purple loosestrife, but when Zimek walked by Lietha’s home, he asked her to dig up the plant in his garden and take it with her. If it was harmful to the native ecosystem, he wanted nothing to do with it.