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My, What Hungry Beetles You Have!

09/30/202609/30/2026

Beetle parent volunteers releasing Galerucella beetles at Maplewood Nature Center. Photo Credit: Abby Tekiela, South Washington Watershed District

Utilizing Beetles to Manage Purple Loosestrife in the St. Croix Watershed

What is Purple Loosetrife?

Purple loosestrife is an invasive semi-aquatic plant that grows in wetlands, along lake shores and rivers, and in roadside ditches. A single purple loosestrife plant can produce over 2 million seeds per year, allowing the species to rapidly spread and outcompete other flowering wetland species native to North America. One solution to this problem includes very hungry beetles – Galerucella beetles, that is! Galerucella beetles are a genus of beetle native to Europe and Asia that were introduced to Minnesota and Wisconsin as a biological control for purple loosestrife in the late 90’s. As an officially approved biological control by the USDA, Galerucella beetles are proven effective at decreasing the density of purple loosestrife stands while also not posing harm to our native plants in North America.

A Galerucella beetle.
Photo Credit: Abby Tekiela, South Washington Watershed District

How is Wild Rivers Conservancy addressing Purple Loosetrife in the St. Croix Watershed?

In 2022, the Conservancy started the Purple Loosestrife Biocontrol Volunteer Science Project, which combines passionate volunteers with purple loosestrife management. Dedicated volunteers, otherwise known as beetle parents, are provided with all materials necessary to raise and release Galerucella beetles, including purple loosestrife plants, starter beetles, netting, and a kiddie pool. The kiddie pool acts as a DIY wetland and allows the plants to take up water via their roots, just as they would in their natural environment.

Invasive species interns Hadlee and Hayden collecting Galerucella starter beetles for distribution.
Photo Credit: Maria Young

After receiving plants, netting, and kiddie pools in May, volunteers take care of the plants until they grow green and leafy enough to support their starter beetles. Volunteers will add their beetles to the plants in June, and wait for the beetles to lay eggs on the plants. The larvae that hatch from these eggs will eventually pupate in the soil of the plants before emerging as adult beetles, typically in mid to late July. The Conservancy then hosts multiple mass release days, where volunteers can gather to release their beetles in locations with dense purple loosestrife stands. In 2026, Wild Rivers Conservancy hosted three mass release days in the St. Croix watershed.

2026 group Galerucella beetle releases

Purple loostrife plants cover a wetland. Photo by Katie Sickmann

1,490

beetles released

At Maplewood Nature Center

700

beetles released

At Serenity Shores

1650

beetles released

At Shafer Baseball Field

Beetle parents who were not able to release their beetles during any of the mass release days also have the option to release their beetles on their own at a pre-approved location. Some of these locations in 2026 include the Lake De Montreville boat launch in Lake Elmo, MN, the North Center Lake boat launch in Center City, MN, and along Sturgeon and Island Lakes in Pine County, MN. In total, 10,000 beetles were released in the St. Croix watershed in 2026.

Thank you to all our dedicated beetle parent volunteers in 2026! If you are interested in becoming a beetle parent in the future, be sure to sign up for our volunteer newsletter to be alerted when sign-ups open in 2027.