Nature Saves Trees from Gypsy Moths: Fungus Helps Stop Spring Caterpillars Cold
Ferrechio, Susan, The Washington Times (Washington, DC)
The annual threat of massive defoliation by gypsy-moth caterpillars barely surfaced this spring, thanks in part to an obscure but deadly Japanese fungus.
The fuzzy caterpillars traditionally turn their appetites on area trees between April and mid-June, stripping bare most of the foliage in their paths with a distinctive munching audible during the night.
But the trees have been silent this spring.
"This is one of the quietest years we've experienced," said Robert Tichenor, chief of the Maryland Department of Forestry's pest-management program, which oversees the control of gypsy-moth infestations.
The state has sprayed insecticides, two chemicals called Dimilin and B.T. , on less than 11,000 acres this spring, down from 40,000 acres in 1996 and more than 100,000 acres in 1991, Mr. Tichenor said.
"It's a great break for the trees," said Phillip Madden, who inspects trees in Southern Maryland for the state's Department of Agriculture.
In Fairfax County, officials have grounded the pesticide airplanes this year after spraying 6,000 acres in 1996 and nearly 40,000 acres in 1995.
"This is the first time we haven't had an aerial treatment program," said Frank Finch, a naturalist with the Fairfax County gypsy-moth program, which was established in 1983.
Mr. Finch and other area gypsy-moth experts said the pest has been subdued, albeit temporarily, with the help of Entomophaga maimaiga, a Japanese soil fungus that gets inside the caterpillar and kills it.
The fungus was unleashed in the United States in the early 1900s to curb a gypsy-moth outbreak in Massachusetts. The caterpillar made its debut there after escaping out the window of a scientist's Medford home in the late 1860s.
The fungus didn't stop the moths. They munched their way through the neighborhood and down the East Coast, where they have most recently begun defoliating trees in North Carolina. But the fungus resurfaced in the soil last year and is believed to have helped curb this year's outbreak.
"I'm sure the fungus is part of the picture," said Mr. Tichenor, who added that two spring frosts killed many caterpillar eggs.
At their worst, the caterpillars can strip the leaves off dozens of acres of trees, leaving giant bald spots on the horizon and depriving other vegetation, animals and people of shade and shelter.
Their appetites are more than a nuisance - repeated defoliation kills many trees, especially the oak and beech species preferred by the caterpillars. …