Tackling Purple Loosestrife—Kenosha to Cornucopia!

Tackling Purple Loosestrife—Kenosha to Cornucopia!

by Derek Strohl, Program Director
Wisconsin Wetlands Association


The most northerly community in Wisconsin is Cornucopia in Bayfield County, and Wisconsin Wetlands Association (WWA) intends to be there this summer. WWA has plans – and funding – to amass a huge volunteer force to survey Wisconsin’s Great Lakes’ 15 coastal counties for purple loosestrife, (Lythrum salicaria).

This European plant, although attractive, has become an aggressive invader of many of Wisconsin’s and other states’ coastal inland wetlands and waterways. Purple loosestrife first appeared in North America in the 1800s, having been inadvertently brought over in Great Lakes ships’ ballast waters, as well as deliberately imported for its medicinal and decorative landscaping uses. This plant reproduces by inundating its environment with seeds, a mature plant producing as many as 300,000 seeds in a season. These tiny seeds can travel by wind and water and can stay viable after being submerged in water for 20 months! But that’s not all – it also reproduces vegetatively, meaning that a part of a plant, even one that has been broken off by a muskrat or a mower, can sprout into a new, healthy, flowering purple loosestrife plant. This prolific and successful reproduction leads to dense infestations on our continent because North America’s wildlife does not consume the plants. Muskrats or other mammals do not make houses out of it, and neither the birds nor the insects here eat it. Basically, this plant is just plain hard to get rid of.

The proliferation of roads across North America carried purple loosestrife across the continent during the last century. The ditches that run along the roads, with their wet, highly disturbed soils, make a perfect habitat for purple loosestrife, and the use of lots of cars and trucks on those roads, each making its own little gust of wind as it zooms to its destination, explains why purple loosestrife infestations often follow the roadways.

Taking Action

A thorough survey of the species’ distribution has not been undertaken for 15 years. A grant from the Wisconsin Coastal Management Program will allow WWA to facilitate this massive public initiative. Local training sessions for volunteers in each coastal county are planned in July. DNR and WWA staff and local resource specialists will teach volunteers how to distinguish the plant from its look-alikes, how to estimate the size and density of an infestation, and how to conduct the field survey. In August, when the plant is in full bloom, volunteers will be asked to spend part of a day surveying a specific area pinpointed on a county map. Surveyors may choose to observe by car, by foot, by boat, and/or by canoe!

All of the data we collect will be assimilated into a database and mapped by the Great Lakes Indian Fish and Wildlife Commission (GLIFWC). Check out their invasive plant website at: www.glifwc-maps.org. Citizens who wish to participate in local efforts to control this plant will be able to use the Internet information to assist them in pinpointing zones of high infestation in order to target their control efforts.

Control Measures

Several methods are currently recommended for use in controlling purple loosestrife. Traditional methods, including plant removal and careful pesticide application, may be used to control populations that are small and not dense, but the only effective and affordable method for controlling large infestations is introducing a beetle that eats purple loosestrife – a method known as biological control. People can purchase a few Galerucella beetles, raise them on an enclosed, potted purple loosestrife plant, and allow them to multiply, producing thousands of beetles within about six weeks. The beetles are then released in an infested wetland, and they become a regular part of the ecosystem, consuming purple loosestrife wherever they find it. The beetles can then be harvested in the spring in order to raise more for another release. The updates to the purple loosestrife GIS will include the locations where Galerucella beetles have been released already. Galerucella beetles are native to the places where purple loosestrife originates, and they are the reason that purple loosestrife is not an “invasive” plant in Europe.

You can learn more about the purple loosestrife bio-control program at: – www.dnr.state.wi.us/org/land/er/invasive/info/loose2.htm,
– www.inhs.uiuc.edu/chf/outreach/VMG/ploosestrife.html,
– www.miseagrant.org/pp/, and
– www.invasiveplants.net/.


In addition to the surveys, we’re coordinating three workshops on the bio-control methodology this fall for citizens and grassroots groups who want to get involved in controlling the plant. Prospective cooperators will be trained in the ecology of the insect’s life cycle and in techniques of raising and releasing the beetles. A part of each workshop will be targeted toward teachers who will receive an introduction to our publication, See Cella (pronounced Chella) Chow: A Purple Loosestrife Biocontrol Manual for Teachers. This publication, containing the 15 activities that we developed last summer, will be printed this summer. We hope teachers who participate will use the biological control program to teach their students about insect life cycles, invasive species, and other ecological concepts. For more information, contact the Wisconsin Wetlands Association at (608)-256-4562.



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Images courtesy of Steven Huyser-Honig,
West Grand Boulevard Collaborative, & Yellow Dog Watershed Preserve.