By Tom Boisvert

Conservation Program Manager, Lincoln County Land Services Dept.

LAKE MOHAWKSIN – As the days warm and our Northwoods summer kicks into high gear, many of us will form lasting memories on some of the most beautiful waters in the state.

The Northwoods is fortunate to have healthy waterways with a wide range of native plant species along the shorelines. Native plants provide habitat for birds and fish, sequester excess nutrients and protect against shoreline erosion. One of the best ways to protect our waters is to preserve existing native vegetation and prevent invasive species from taking hold.

One of these invasive species to be aware of is purple loosestrife (Lythrum salicaria).

Purple loosestrife is an attractive flower that reaches six feet tall and has pinkish-purple flower spikes in mid-summer. This plant used to be sold as an ornamental water garden plant, but quickly escaped and began spreading into the wild. As a non-native species, it has no local predators and easily multiplies to take over wetlands, shorelines and roadside ditches.

To keep purple loosestrife from crowding lakeshores, many lake groups are cooperating with conservation organizations to take steps to control this plant.

One of the best tools at our disposal is a tiny ally, a beetle native to the same part of Asia as purple loosestrife itself. This insect specifically feeds on the leaves and stems of purple loosestrife. This weakens the plant so it develops extremely low numbers of seeds, if any at all. This helps to contain the plant’s numbers and gives our native shoreline plants a fighting chance.

Purple loosestrife beetles have been studied in North America and the Midwest for more than 30 years and have been used on the landscape since the mid-1990s. There is no documented example of these beetles feeding on any other plant species. They are extreme insect specialist feeders, just like the monarch butterfly needs milkweed and no other plant.

One of the local groups working to control purple loosestrife on their shoreline is the Friends of Lake Mohawksin. They have partnered with the Wisconsin Headwaters Invasives Partnership (WHIP). WHIP is a nonprofit group serving Lincoln, Oneida and Vilas Counties comprised of 16 groups cooperating to battle invasive species.

With funding supported by WEC Energies, WHIP has set up purple loosestrife rearing plants on properties of landowner volunteers and will raise beetles under netting until mid-summer. These beetles will then be released into purple loosestrife patches to keep the invasive plant numbers down.

If you see tall purple flowers waving in the wind on your land this summer, you may have purple loosestrife. To keep it from spreading, snip off flower stalks before they go to seed and dispose in secure trash bags.

If you would like help identifying or controlling this plant, contact the Wisconsin Headwaters Invasives Partnership at 313-590-4419 or the Lincoln County Land Services Department at 715-539-1054.

By working together and using multiple techniques, we can help our waterways stay as natural and healthy as possible.