Lake Photo

Purple Loosestrife, another aquatic invasive species, is present on the Eagle River Chain

What is it?

Purple loosestrife is an attractive shoreline/wetland plant native to Europe and Asia where insects and diseases native to that area have kept it in check. It was introduced to North America without its natural controls as a garden plant, and has since spread to wild areas and depleted natural habitat of native plants and animals.

Purple Loosestrife grows taller and faster than our native wetland plants. It displaces native vegetation and degrades wildlife habitat. Eventually, purple loosestrife can overrun wetlands thousands of acres in size, and almost entirely eliminate the open water habitat. Thick growth of purple loosestrife can be detrimental to recreation by choking waterways, and it can even impede boat travel.

Purple loosestrife is a beautiful perennial herb 3-7 feet tall with a dense bushy growth of 1-50 stems. The stems, which range from green to purple, die back each year. Showy flowers vary from purple to magenta and have 5-6 petals aggregated into numerous long spikes. A single plant can produce millions of seeds annually. It blooms from July to September.

Purple Loosestrife Photo   Purple Loosestrife Photo   Purple Loosestrife Photo


What are we doing about it?

In 2012, Ted Ritter, Vilas County Invasive Species Coordinator at that time, launched a multi-partner community effort to begin controlling purple loosestrife plants in the Eagle River area. The project employed Galerucella beetles as biological control agents to reduce the growth and reproduction of plants established in the area.

According to Ted, "The advantage of biological control is that the beetles eat nothing but purple loosestrife. They burrow into the plant root crown for the winter as the plant tops die back in the fall. As the plant re-emerges in the spring, the beetles travel up the stems and mate heavily for several weeks. Continued eating by the ever increasing beetle population takes a heavy toll on the plants. While mortality of the plants at a given site is not always achieved, the inability of the plants to flower and produce seeds stops the otherwise rapid spread of the plant population."

"The beetle depends entirely on purple loosestrife plants for survival and reproduction," explained Ted. "Having the ability to fly only short distances to other nearby host plants, the insects have proven not to be pests to other plants, animals or humans. Without purple loosestrife plants to live on, the insects die. This method of bio-control has been employed in Wisconsin for more than 10 years without adverse effects," he added.

The community project involved the partnership of the Eagle River Chain of Lakes Association, students from Northland Pines High School, and the Vilas County Land and Water Conservation, Mapping, Forestry and Highway Departments.

NPHS students dug purple loosestrife roots in May, 2012 as part of the school's Earth Day recognition. The roots were taken to the Vilas County Forestry / Highway Departments grounds on Highway 45 North where the students planted them in 50 pots. They were fertilized, wrapped with fine mesh nets and placed in shallow pools of water where they rapidly grew to large plants.

Purple Loosestrife Photo   Purple Loosestrife Photo

Purple Loosestrife Photo   Purple Loosestrife Photo

Volunteers collected 500 Galerucella beetles in early June from plants where a bio-control project has been underway the past several years. Ten beetles were released in each netted pot and reproduced to approximately 50,000 beetles in six weeks.

Purple Loosestrife Photo   Purple Loosestrife Photo

The plants were nearly destroyed by the beetles which rely exclusively on purple loosestrife plants for food and habitat.

In July, 2012, the netted pots and beetles were transported to established population sites on the Eagle River Chain where the beetles were released to control populations of purple loosestrife. The beetles burrow into the root crowns of the plants during fall, then awaken the next spring to continue reproducing and eating the leaves of their host plants. Beetles were harvested and released again in 2013 and 2014.

In 2016, Cathy Higley, Vilas County Invasive Species Coordinator, repeated the program. Click here to learn what was done.

What is next?

Eagle River Chain of Lakes Association volunteers will continue to annually monitor and mark GPS waypoints where purple loosestrife and other shoreline invasive species are noted.

What can you do?

Prevention is the easiest control method and the best way to stop the spread of purple loosestrife. Monitor your shoreline annually and remove any new young plants. Plants are most easily located when flowering. One mature PL plant produces over 2 million seeds a season, so learn to recognize pre-flowering plants or search for them when they just start to bloom. Destroy plants before they flower and drop seeds. When removing plants, take care not to leave stems or cuttings that can resprout or disperse viable seed.

Anyone in the Eagle River area having purple loosestrife plants on their property is encouraged to contact Cathy Higley at the courthouse in Eagle River at 715-479-3738.

Click here for a map of Purple loosestrife locations.

More information can be found on the WI DNR website at:

Purple Loosestrife

Purple Loosestrife Monitoring and Biocontrol

Purple Loosestrife Publication



Other Wetland Plants of Concern

At more than 120,000 acres, wetlands account for approximately 19% of Vilas County's landscape. About one third of Vilas County is covered by either surface waters or wetlands.

Wetlands are capable of handling and neutralizing many environmental stresses. But one of their enemies is invasive species. Certain plants capable of causing harm to wetlands are showing up across the state.

Are you familiar with plants such as garden loosestrife, yellow iris, or common reed grass, all of which can now be found scattered throughout Vilas County, or flowering rush which has recently been found in northern Oneida County, but not yet reported in Vilas? We need to be on the lookout for these wetland threats.

Click here for more information and to see pictures of these wetland plants.


Click here for a map of yellow iris locations.

Click here for a map of yellow loosestrife locations.