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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

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June 2001

Purple invaders

How ghosts and beetles in the backyard help control the spread of purple loosestrife.

Brock Woods and Cathy Cleland

Table of contents
Weed Warriors: Volunteers keep watch for Eurasian water milfoil

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.

Table of Contents

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.

Weed Warriors:Volunteers keep watch for Eurasian water milfoil
Self-Help Lake Monitoring volunteers have been the backbone of water quality testing in Wisconsin since 1986. In fact, today about 650 Wisconsin volunteers invest their time and energy to help with everything from taking secchi readings that monitor water clarity to collecting water chemistry samples, taking dissolved oxygen readings and monitoring aquatic plants.

Now, many of these volunteers also have answered the call to be weed warriors in a battle against Eurasian water milfoil. Many, but not all, of the weed watchers are Self-Help volunteers.

Weed watchers are trained by the Department of Natural Resources or University of Wisconsin-Extension to distinguish native aquatic vegetation from the exotics and in particular to differentiate the Eurasian variety from the seven species of native milfoil. Early identification makes eradication or control much easier and can help prevent its spread. The most recent information available from Oct. 2000 shows that Eurasian water milfoil is found in 54 of 72 Wisconsin counties.

Volunteers receive a packet containing fact sheets, reporting forms and a laminated sample of Eurasian water milfoil. The weed watchers motor around their chosen lake once or twice a summer on clear, calm days checking plant beds and raking up suspect plants.

Since Eurasian water milfoil can grow in water up to 20-feet deep, volunteers check both the near shore areas and deeper water. In particular, areas near boat landings are carefully inspected since boats are the primary carrier of Eurasian water milfoil to other waters.

If the exotic water milfoil is present, fragments may wash up on beaches, so volunteers also thoroughly check these areas. When volunteers find a plant they think is Eurasian water milfoil, they share their findings with a plant expert, usually their local Self-Help coordinator. The plant is verified and the results entered into a DNR database.

One observant volunteer weed warrior, for example, found a fragment of Eurasian water milfoil near the boat landing on Lake Minocqua in Oneida County last September. This was the first report of the exotic on this lake. The plant was verified and the lake association hired a diver to remove the Eurasian water milfoil plants near the boat landing and dispose of them. With luck, the diver found and destroyed the aquatic exotic intruder in this bay. Plant surveys will be done in the future so a control strategy can be worked out if Eurasian water milfoil is found again. Early identification is essential in this battle.

Contact your local DNR Self-Help Coordinator if you are interested in becoming a weed warrior.

-- Sandy Wickman is a Self-Help Lake Monitoring Program Assistant in the DNR's Rhinelander service center.