Great Lakes Article:

Beetles enlisted to trim back loosestrife

County to breed bugs; invasive plant is threat to native species

By LINDA SPICE
Article courtesy of the Journal Sentinel

Dec. 2, 2001

Before Milwaukee County can launch its ground attack against an exotic plant invading the county's wetlands, it must first breed its troops: a pack of 100 beetles expected to grow to 10,000.

Parks official have put in a $25 order to the state Department of Natural Resources for the Galerucella beetles, native to Europe and Asia, that they plan to mate in April and launch next summer into county parks infested by purple loosestrife.

The DNR introduced the biocontrol technique for the first time in Wisconsin in 1994 in Shawano and Jefferson counties, where beetles were first released. Since then, several other counties, such as Monroe, Door, Juneau and Fond du Lac, have used the method with some success.

Wisconsin is among 35 states using beetles against the purple loosestrife since 1992, according to Brock Woods, a research ecologist for the DNR. He noted that the southern unit of the Kettle Moraine State Forest near Eagle as well as areas in Rhinelander and Spooner, hit the worst in the state by infestation, will be the first to each undergo a mass rearing and release of 100,000 beetles next summer.

"The purple loosestrife is an invasive plant that chokes out native Wisconsin plants," said Milwaukee County Supervisor Jim McGuigan, who first noticed the invasion of the weed to the Little Menomonee River Valley in the informally named North Lake Park, just north of Brown Deer Road near N. 104th St.

"There is a large stand of purple loosestrife that are expanding," he said. "It's a tall plant, about 4 feet tall, so it robs (native plants) of sunlight."

Though beautiful in its purple flower bloom, said county land manager Dan Spuhler, the plant can kill off native species and displace wildlife if left unchecked. His office is working to identify areas in the county where the plant exists, and so far has found it not only in North Lake Park but also a small site in Whitnall Park and near the Root River Parkway.

"They produce enormous amounts of seeds and they are incredibly aggressive growers and will out-compete native vegetation in these wetland areas," he said. "They will destroy the wetland habitat by turning it into a monoculture of purple loosestrife. There will no longer be food, no longer nesting sites."

Spuhler said the plant was introduced in the United States in the early 1800s from Europe. It came over for use in flower gardens but is also suspected to have been transported in soil used for ballast of ships, officials said. But without its natural beetle predator, the perennial plant can produce up to 2 million seeds, which Spuhler said can remain viable for up to 40 years in the muck of wetland soils.

At risk are sedge, bulrush and other native wildflowers, such as trillium and black-eyed Susan, according to Spuhler and McGuigan.

The county will rear the beetles in some type of tub or basin that will hold living purple loosestrife plants, Spuhler said. A netting over the plants will serve two purposes. One will be to ensure that the beetles stay on the plants and are in close proximity to each other to find a partner. The second is to prevent predatory insects and birds from "feeding off of our little hatchery," Spuhler said.

The beetles and their offspring will feed off the plants between April and July, when parks officials will collect some of them and release them at different sites. The beetles are 4 to 5 millimeters long as adults and are light tan in color.

While the beetle feeds on the plant, helping curb its spread, it will not eliminate the plant entirely. Spuhler said the beetles can reduce any infestation to a level where the wildlife habitat and native plant species are at very little or no risk.

Spuhler said residents should not worry that once the beetle takes care of the plant they will have to worry about an overpopulation of beetles. He explained that the beetle needs the plant to live and with fewer plants will come fewer beetles.

"So when the purple loosestrife goes away, the beetles will die out," he said.