Gypsy Moths, the plant-eating pests, keep spreading north and west across Wisconsin.

The quarantine zone now stretches from lake Michigan to the Wisconsin River.

That means more than half of the counties in the state are affected. The latest additions are Dane, Adams, Marquette, Lincoln, Oneida, Vilas and Marathon counties.

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Facts about the Gypsy Moth

• The species originally evolved in Europe and Asia and has existed there for thousands of years.

• In either 1868 or 1869, the gypsy moth was accidentally introduced near Boston, MA by E. Leopold Trouvelot.

• The gypsy moth is known to feed on on the foliage of hundreds of species of plants in North America but its most common hosts are oaks and aspen.

• Gypsy moth hosts are located through most of the coterminous US but the highest concentrations of host trees are in the southern Appalachian Mtns., the Ozark Mtns., and in the northern Lake States.

• Gypsy moth populations are typically eruptive in North America; in any forest stand densities may fluctuate from near 1 egg mass per ha to over 1,000 per ha.

• In most northeastern forests, less than 20 percent of the trees in a forest will die but occasionally tree mortality may be very heavy.

• Over the last 20 years, several millions of acres of forest land have been aerially sprayed with pesticides in order to suppress outbreak gypsy moth populations.

• In 1992, the USDA Forest Service began a pilot program to test the feasibility of slowing the spread (STS) of the gypsy moth in North America. STS pilot programs currently exist in North Carolina, Virginia, West Virginia, and Michigan.

Source:www.fs.fed.us/ne/morgantown/4557/gmoth/ contributed to this report