Beetles enlisted to trim back loosestrife
County to breed bugs; invasive plant is threat to native
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
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
"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
At risk are sedge, bulrush and other native wildflowers,
such as trillium and black-eyed Susan, according to Spuhler
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,"
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.