Gypsy moths creep into Wisconsin Department of Agriculture to spray parts of
Steve Tomasko The Daily Press
Photo courtesy U.S. Forest Service
MUNCH MUNCH — Gypsy moth caterpillars
have been known to eat the leaves of about 500 different
tree and shrub species. The destructive exotic pests
have defoliated millions of acres of forest in the Eastern
United States and are making a headway into
Like a slow advancing army, Gypsy moths
are creeping into Wisconsin
and have reached the Bayfield
and officials are set to try and slow them down.
The U.S. Forest Service plans to spray
close to 60,000 acres of forest this spring with a chemical
that will disrupt the moth's mating patterns.
The compound is a pheromone, a chemical
the female moths exude to attract males. By dousing
areas of the forest with the chemical, which goes by
the name of Disparlure, foresters hope to confuse the
mating habits of the moths.
Pilots will spread the pheromone by
plane over about 50,000 acres of National Forest in
the Washburn Ranger District and another 7,000 acres
in the Park Falls-Medford District.
Steve Millett, Gypsy Moth Program coordinator
for the Wisconsin Department of Agriculture said the
state has proposed to treat up to 344,000 acres for
forest land in the state, including state, federal and
private forest land. The treatments range from Janesville
in southern Wisconsin
to the Bayfield
It's the largest acreage that's been treated in the
state so far.
The majority of treatments will be
with pheromone flakes, although some areas will receive
sprays of Btk (Bacillus thuringiensis var. Kurstaki),
a bacterial insecticide that only effects certain kinds
Since the pheromone is specific to
Gypsy moths, it's considered practically non-toxic to
other insects, birds and other animals.
Only tiny quantities are needed to
disrupt the critter's mating habits. The compound is
attached to small plastic flakes and will be spread
at a rate of about one-half cup per acre.
The reason for the action is to attempt
to slow the advance of Gypsy moths, which can munch
on hundreds of varieties of tree and shrub species and
cause massive defoliation.
Since its introduction near Boston
in 1869, the Gypsy moth has spread to all or part of
17 states and the District of
Columbia. Yearly defoliation
often reaches into the millions of acres, and the costs
of damage and control run into tens of millions of dollars.
The treatment program is part of a
nation-wide effort to slow down the advance of Gypsy
moths called the National Gypsy Moth Slow the Spread
The name of the project admits that
the moths can't be eliminated, said Andrea Diss, Gypsy
Moth Program coordinator for the Department of Natural
"We can't stop the Gypsy moth,
that's why it's not called stop the spread program,"
The goal of the project is to use whatever
strategies are available to at least slow down the advance
of the insects until new research can come along to
help gain more control.
The STS project focuses on low-level
populations in the transition zone between areas considered
generally infested and generally uninfested -- which
is where Wisconsin sits.
Since female Gypsy moths don't fly,
they haven't advanced as rapidly as some other exotic
invaders. The newly-hatched caterpillars can sometimes
travel long distances by "ballooning," catching
a ride on the wind with long streamers of silk.
But humans are probably the main, if
unintentional, culprits in helping the moths move to
The females will lay their egg cases
anywhere, on nursery stock, the undercarriages of any
vehicle, firewood or outdoor furniture.
DNR silviculturalist Mark Theisen said
the pheromone treatments should definitely have an impact
on knocking back the moth populations. Like Diss, however,
he admits the moths won't be eradicated from the state.
The treatments will hopefully slow
the critter's advance enough to allow native predators
to develop a taste for the caterpillars and moths, he
Gypsy moth tidbits
Many exotic pests came to the United
States inadvertently: in the ballast water of ships,
in shipments of produce or other imports, even as seeds
on traveler's shoes. The Gypsy moth, however, was brought
over from Europe intentionally.
In the 1860s, French immigrant Ettiene
Leopold Trouvelot settled in
working-class suburb of Boston.
An amateur entomologist, Trouvelot
brought some Gypsy moth egg masses back from France
in an attempt to culture them for silk production on
trees in back of his house.
Some of the larvae escaped and they
have been slowly marching westward ever since.
Like many exotic invaders, Gypsy moths
left their natural enemies behind in their native land
and were able to spread quickly with little natural
Gypsy moth caterpillars have pairs
of red and blue spots along their back, long dark hairs
and are present from May until early July. The caterpillars
spin reddish-brown cocoons in July and pupate for one
to two weeks.
Adult moths live only a few days and
do not feed. Adult males are brown with dark markings
on the wings and are active fliers. Adult females have
white wings with black chevron markings, but do not
fly. Adults may be present in July and early August.
Each female lays one tan egg mass, which is covered
with tiny hairs. Egg masses may be small, about the
size of a quarter, or may be up to three inches long.
Egg masses are laid in July or August and will hatch
the following April or May.
Gypsy moth caterpillars are not at
all finicky eaters. They can eat the foliage of 500
species of trees and plants.
Their preferred tree species for snacking
on include alder, apple, aspen, basswood, white birch,
box elder, hawthorn, oaks, tamarack willow and witch
hazel. Second on their list are beech, black birch,
yellow birch, butternut, cherries, chestnut, cottonwood,
elms, hemlock, hickories, ironwood, juniper, maples,
pines, spruces and walnuts.
Some of the few species they do avoid
are ash, balsam fir, cedar, red and white dogwoods,
locusts, mountain maple, and scotch pine.
Each caterpillar can consume up to
11 square feet of foliage from early May until June.
For more information on this subject,
check out these resources: • Wisconsin DNR Gypsy moth
website • U.S. Forest Service "Slow the Spread"
Gypsy moth program