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August 2, 2011

MADISON - Purple loosestrife is in full bloom across Wisconsin and state invasive species officials are asking for citizens to help control these invaders.

"Purple loosestrife is easiest to find when it's flowering," says Brock Woods, who coordinates Wisconsin efforts to control purple loosestrife. "This is a crucial time to prevent this invasive plant from spreading and taking over wetlands and other special places."

One mature purple loosestrife plant produces more than 2 million seeds a season, so removing the plants while they're blooming and before they go to seed is very important, he says.

Purple loosestrife displaces native wetland plants and degrades wildlife habitat. Eventually, purple loosestrife can overrun wetlands thousands of acres in size. By law, purple loosestrife is a restricted invasive species in Wisconsin. It is illegal to sell, buy, transport introduce and transfer.

Citizens can help control purple loosestrife by reporting all infestations to DNR and pulling young plants and cutting off the flowering tops before they go to seed. They can also help by releasing special beetles that eat only purple loosestrife.

Report sightings of purple loosestrife and other invasive plants

Sightings of purple loosestrife on public land or private property can be reported to the DNR. Report populations of purple loosestrife and other invasive species by emailing the exact location, land ownership if known, population size, your contact information, and a photo or voucher specimen to, or by calling by 608-266-6437. Details on reporting can be found on the DNR website.

Property owners can tackle the invader on their own land

Pulling small, young plants with all their roots sometimes stops permanent plants from getting established. While simply cutting off the flowing tops of older plants before they go to seed eliminates this year's seed crop, treating the stem stumps with herbicide provides a longer-lasting solution, Woods says.

If there is open or standing water at or very near the plants, use an herbicide labeled for use near water and get an aquatic plant management permit from the local DNR aquatic plant management coordinator.

Plants and seeds should be carefully bagged and sent to a landfill. Composting will not kill the seeds.

An information sheet with photos of these and many other invasive wetland plants (pdf) is available online, as is more detailed information about many invasive plant species.

Raise and release biocontrol beetles

Free equipment and starter beetles are still available to anyone interested in helping raise special beetles that eat only purple loosestrife.

DNR and the University of Wisconsin-Extension, along with hundreds of citizen cooperators, have been introducing natural insect enemies of purple loosestrife, from its home in Europe, to infested wetlands in the state since 1994.

Careful research over two decades has shown that these insects feed on purple loosestrife and are not a threat to other plants, Woods says. Insect releases monitored in Wisconsin and elsewhere have also shown that these beetles can effectively decrease purple loosestrife's size and seed output, thus letting native plants reduce its numbers naturally through increased competition.

Most beetles have been raised and released by citizens using a simple backyard process and free gear from DNR. Equipment and starter beetles are available in spring to anyone interested in helping to raise special beetles for their area. Field site and plants for rearing should be chosen yet this summer.

People interested in raising the beetles can learn more about the project on the purple loosestrife biocontrol page of the DNR website, and can contact Woods at (608) 221-6349 or for details.

FOR MORE INFORMATION CONTACT: Brock Woods (608) 221-6349; Kelly Kearns (608) 267-5066

Last Revised: Tuesday, August 02, 2011

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