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Purple loosestrife biocontrol — and you

Purple loosestrife is large flowering plant that is listed as a Restricted invasive in Wisconsin because of its history of causing negative ecological impacts to wetlands and shorelines. Extensive populations of the plants that were found throughout the state in the later half of the 1900’s have been brought down to manageable level in most areas thanks to tiny beetles and the people who rear and release them where needed. 

Wisconsin DNR has been using four of its insect enemies, also from Europe, to control it here since 1994. Careful research has shown that all four control species depend only on loosestrife and do not threaten native plants. This is classic biocontrol, and it is likely the best long-term control for loosestrife, reducing the need for other more costly and disruptive controls, such as herbicides.

"Cella" beetle species (Galerucella calmariensis and G. pusilla) feed on leaves and shoots and are the most effective of four types of imported insects. A root-boring weevil, Hylobius transversovittatus, was released early in the program and has been difficult to monitor for success. A second weevil, Nanophyes marmoratus, feeds on the flowers and appears to have naturalized since being released early on during the three-decade biocontrol program. 

Cellas are the easiest species to intentionally rear and place where they are needed. They successfully decrease the vigor, size and seed output of purple loosestrife, allowing native plants to survive and compete against the remaining purple loosestrife which can provide some benefits to pollinators when it is not eradicated. Effective biocontrol typically ranges from one to several years, depending on such factors as site size and purple loosestrife density. Though elimination is rare, biocontrol offers effective and environmentally sound control of the plant without herbicides.

You can help control purple loosestrife

Since 1997 hundreds of volunteers across the state have shared in the fun of rearing Cellas and releasing them into local purple loosestrife populations which occur in wetlands, lake and river shorelines and ditches. Starting out with ten beetles per plant, you can rear up to 1000 to release in just a few months. WDNR provides the netting to ‘cage’ the plants, but people generally provide other supplies themselves. Below you can learn more about the process which people often do in their own backyards or at local schools with the help of their County’s Aquatic Invasive Species Coordinator. Check our Aquatic Invasive Species Contacts page to find yours. 

A Purple Loosestrife Biocontrol permit is required because the process involves moving a WI Restricted invasive species from one location to another. The application can be found below in the Forms section.

Because Galerucella beetles are now naturalized throughout Wisconsin, WDNR does not provide the parent beetles for rearing or releases. However, County Aquatic Invasive Species Coordinators and the Statewide Coordinator can assist in finding parent beetles in most cases. Training to find your own is available, too, and possibly the most fun of the process!   


Help UW Madison Division of Extension Natural Resources Institute’s Aquatic Invasive Species Program evaluate our training videos and their use by taking this survey after you watch this and other videos in the series: Purple Loosestrife Training Follow Up Survey. You can repeat the survey for each of the videos in the survey or watch multiple videos and reply for all of them at once.


Educational materials for students:

  • See Cella Chow! Here you’ll find lesson plans for grades 6-12 built around the science of biocontrol, specifically purple loosestrife. The lessons include a listing of the related Wisconsin Model Environmental Education and Science Standards.

Purple loosestrife is here to stay in Wisconsin, but you can help protect your wetlands from domination by this exotic invader by simply reuniting it locally with its natural predators! And as biocontrol reduces your loosestrife, you'll experience even more satisfaction by helping to restore any native plants the loosestrife may have eliminated locally, further ensuring diverse, healthy wetlands!

For more information

Purple Loosestrife Biocontrol Coordinator
Purple Loosestrife Project
101 S. Webster St., WY/4
PO Box 7921
Madison, WI 53707-7921

Training Opportunities

To find learn if there is an upcoming training near you, contact the program coordinator or your county Aquatic Invasive Species Coordinator. The County Coordinators can be found at Wisconsin DNR AIS Contacts. Some counties may not have a coordinator, but there could be training in a county nearby.