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Last spring, you may have wondered about some strange ghost-like objects standing in a child's wading pool in someone's back yard. Wondered, but were afraid to ask?
Put your fears to rest. They weren't ghosts but net insect bags containing a purple loosestrife plant and hundreds or thousands of helpful beetles.
And not just any beetle, but a species that feeds specifically on purple loosestrife.
All too often, purple loosestrife is found growing along the fringes of wetlands, waterways and roadsides in 70 of Wisconsin's 72 counties. Despite its beauty, it aggressively displaces native plants and devastates shoreline and wetland habitats. This plant originated in Eurasia and arrived in North America in the 1800s by way of ship ballast and as a garden plant brought over by immigrants.
Eradicating this exotic has proven difficult.
Once established, purple loosestrife forms a dense tangle of roots and stems, crowding out native plant species and wildlife. Mature plants can produce from 100,000 to 3 million seeds per plant per year, which creates a huge seed bank viable for years. Traditional removal methods such as hand pulling, burning and chemicals are labor intensive and, though very useful for containing small populations, have had limited success for larger infestations.
As a result, experts are increasingly turning to nature for a solution.
In Eurasia, the plants are kept in check by insects that feed on them. After years of rigorous testing to be sure they would only feed on purple loosestrife, several of these insect species were approved for release in the United States with the hope that they could help control the plant here. In 1994, DNR biologists began releasing some of these insects in Wisconsin. Monitoring release sites has shown the insects are an effective, natural and safe control for this exotic plant.
Two species of Galerucella beetles show particular promise in both reducing the plant's spread and rendering it less competitive with native plants. Beetles decrease flowering and seed sets by feeding on the developing stem. Leaf feeding also weakens purple loosestrife, helping native plants choke it out.
The Department of Natural Resources, through the Purple Loosestrife Biocontrol Project, has enlisted help from students, scouts, lake associations and individuals in raising the beetles for release since 1997. Over a 1.5 million of these beetles have been released in more than 200 sites statewide by these cooperators. Monitoring these sites has shown the beetles to be an effective, natural control for this exotic plant.
Notable assistance has come from two other parts of the state. Since 1998, Barron County seasonal worker Dave Blumer has not only released beetles in many sites in and around the county, but also has recruited teachers in most of the county's secondary schools to do the same. In 1999, DNR staff at the Rhinelander Service Center began a northern hub of this activity. They began raising beetles while working with cooperators like John Bie from Woodruff and providing plants for raising beetles to the Lucky Hills 4-H group in Taylor County. Since then, the center staff has released many beetles, in addition to helping other cooperators get started.
Many other special biocontrol efforts were integrated with traditional methods. For example, in 1999 Lori Regni, from the Post Lakes Protection and Rehabilitation District, spearheaded a campaign to eradicate loosestrife from Langlade County. Informational literature was distributed, residents were asked to remove purple loosestrife from their shorelines, a group was organized to remove flowering tops and dig purple loosestrife from the shores of Post Lake in 1999, filling three rowboats. In 2000, the project continued as Regni arranged to have more than 20,000 beetles raised and released in the Post Lake area.
Other examples include Camp Manito-wish YMCA, where campers and staff have released beetles as well as pulled purple loosestrife along the shores of Boulder Lake for the last two years. At Horicon Marsh, cooperation between Department of Natural Resources and federal workers has resulted in rearing and releasing beetles that reduced purple loosestrife all over the marsh.
Charlie Shong, superintendent of the Lake Pewaukee Sanitary District where beetles have been raised since 1999, says a small investment of time, space and a few materials is all that are required to become involved with biocontrol. Permission is granted to volunteers to grow purple loosestrife as a food source for the beetles, since the cultivation of the plant is banned in Wisconsin. The plants are gathered from local wetlands. Beetles needed to start rearing are either collected from former release sites or acquired from the Department of Natural Resources in Monona or Rhinelander.
The Pewaukee Sanitary District also is partnering with The Lake Country Rotary in Hartland and the Pewaukee Rotary Club to raise and release beetles in the district. To build a future for exotics management, the sanitary district hosts a spring high school summit on exotics species. The high school kids teach others at their schools and even middle schoolers about management options for controlling exotics.
While these beetles will not eradicate loosestrife, they may reduce the population enough that cohabitation with native species becomes a possibility, Shong notes.
Volunteers dig their plants in March and April, put the plants in pots or buckets and cover each with a net insect bag. They are placed in children's wading pools because they require a lot of water to grow. The pools are placed in areas of full sunlight.
Beetles may be acquired from the Department of Natural Resources or collected in May as they emerge from the leaf litter and soil where they've hidden throughout the winter. Ten beetles are placed on each bagged plant where they feed and lay eggs completing their life cycle. The eggs hatch, larvae emerge, feed, pupate, and about 1,000-2,000 new adults emerge from each pot in 7-10 weeks. The pots are taken to a purple loosestrife site where the beetles are released. Project materials are then stowed away until the next spring's rearing. It costs about $200 to $300 to produce 10,000 or more beetles.
The DNR's beetle program will continue as long as there is funding and interest for it. Contact the DNR aquatic plant manager in your region, or the Biocontrol Program Office in Monona at (608) 221-6349, or Brock Woods for more information.
Cathy Cleland works on aquatic exotics issues for the Department of Natural Resources and is stationed in the Rhinelander office. Brock Woods works on the Purple Loosestrife Biocontrol Project out of the DNR's Research Center in Monona.