Last year in Pennsylvania, according to state Department of Conservation and Natural Resources officials, 76,000 acres were devastated by gypsy moths compared to 2.1 million acres the year before.
In Maryland, said state entomologist Robert Rabaglia, the moths chomped through 200,000 acres of forests in the early 1990s. In 1996, the number of acres of defoliated trees was down to 11,000 acres. "This year I don't know if there are any," Rabaglia said.
Tichenor said Maryland spent an average of $1.5 million a year spraying for gypsy moths during the moth's peak years. Only sporadic spraying is conducted now and only on the Eastern Shore, he said.
West Virginia officials determine gypsy moth damage by the number of acres sprayed. The worst year for the Mountain State was 1990, when 364,000 acres, including most woods in the Eastern Panhandle, were sprayed, Hacker said. "We haven't sprayed for two years," he said.
Hacker and his counterparts in Maryland and Pennsylvania list several reasons for the moth's demise. They credit a fungus introduced in the Northeast in the early 1900s to kill the insects. The fungus was dormant for decades until the early 1990s when its effect on the moths was first observed, Hacker said.
Bruce Kile, a service forester at the 83,000-acre Michaux State Forest, which lies in part in Franklin County, Pa., said he counted thousands of gypsy moth caterpillars on a Friday afternoon in 1993. He came back on Monday and all those he saw were dead or dying from the fungus, he said.
Gypsy moths eat the fungus, which creates spores in their systems. When they die the spores are released and become airborne on their way to other moths, Hacker said.
Also, foresters said, a virus that attacks the moths that also was introduced in the early part of the century is taking its toll. The virus is most effective when gypsy moth populations are high, Tichenor said.
Other reasons for the population decline are the wet, cool springs of recent years, which enhanced the survival of fungi. The life cycle of the gypsy moth, with populations building for years, collapsing, then building again, also must be taken into account.
Foresters in all three states said aggressive aerial spraying over millions of acres every spring, at first with powerful insecticides and later with more environmentally friendly biological growth regulators, has had a devastating effect on gypsy moth populations.
"We're not saying it's all over, but it's good news that it's at a 30-year low. Our trees will look normal again" said William Reagan, spokesman for the Penn State Cooperative Extension Office in Franklin County. "We're hoping it stays that way. There may be pockets of defoliation, but it will never get back to like it was."
Gypsy moths hatch in late April or early May and begin eating young leaves. Their favored diet is oak, sugar maple, beech and aspen. Trees defoliated for three consecutive years usually die, foresters said.
Gypsy moths were imported to Massachusetts in 1868. They were supposed to produce silk for the textile industry, but the experiment failed. The first gypsy moths were spotted in Pennsylvania in 1932. The moth has no natural enemies.