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Great Lakes Article:

Gypsy moths creep into Wisconsin Department of Agriculture to spray parts of Chequamegon National Forest this spring

Steve Tomasko The Daily Press
02/17/2002

 

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 Wisconsin.

 

Like a slow advancing army, Gypsy moths are creeping into Wisconsin and have reached the Bayfield Peninsula 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 Peninsula. 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 of caterpillars.

 

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 (STS) Project.

 

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 Resources.

 

"We can't stop the Gypsy moth, that's why it's not called stop the spread program," Diss said.

 

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 new areas.

 

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 said.

 

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

 

Medford, Massachusetts, a 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 control.

 

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

 

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