Trees get reprieve from gypsy moth attacks

Joe Napsha
| Sunday, March 24, 2013, 12:01 a.m.

Gypsy moth caterpillars that have feasted on Western Pennsylvania's trees for 24 years won't defoliate the region's forests this year, sparing the oaks and other hardwoods that have recovered from past infestations, experts said.

“The trees are healthy, and no defoliation of hardwood trees was noted last year,” said Edward Callahan, district forester for the Forbes State Forest, which has 60,500 acres in Fayette, Somerset and Westmoreland counties.

Despite intensive spraying programs that cost more than $17 million from 2006 to 2009 alone, state foresters said, they can't eliminate the pest.

“It's too well established, and is here to stay,” said Richard J. Allan, secretary of the Department of Conservation and Natural Resources.

Ferocious attacks

The 2-inch gypsy moth — it lives about a year and eats leaves in its caterpillar stage — feeds on more that 200 species of trees and shrubs. It defoliates oak, apple, birch, poplar, willow and other trees common to Western Pennsylvania.

Foresters believe the pests will strike in Northcentral and Northwestern Pennsylvania this summer, said David A. Schmit, a forest health specialist for the state Bureau of Forestry.

State, federal and local governments this spring plan to spend as much as $2 million to helicopter-spray BT, a biological insecticide, over about 43,100 acres of state forestland, parkland and Pennsylvania Game Commission land in Cameron, Clarion, Forest, Jefferson, Lycoming, Potter and Tioga counties.

The insecticide, which kills the caterpillars when consumed, also will target 65 acres of private forest in Venango County.

Spraying has not been necessary since 2009 because the gypsy moth's natural enemy, a fungus, caused populations to collapse across the state, said Daniel Devlin, forestry bureau director.

Healing process

About 700,000 acres of woodlands in Pennsylvania were defoliated by the gypsy moth in 2006, according to the state conservation department.

At least half of all oak trees in the state were lost in the initial infestation. Fewer died the following year, as there were fewer leaves to eat and natural predators attacked the gypsy moth, said Kurt W. Gottschalk, research forester for the U.S. Forest Service in Morgantown, W.Va.

Cynthia Walter, an associate professor of biology at St. Vincent College near Latrobe, has headed a gypsy moth research project and worked on long-term ecological studies in forests and streams for more than 25 years.

Trees don't die due to the loss of leaves. Rather, “they often succumb to a fungal infection,” Walter said. The stress of making new leaves and trying to ward off pathogenic fungi can be too much for weakened trees, she said.

The affected areas in Forbes State Forest have recovered, thanks to the variety of trees in Pennsylvania, along with fungus, pesticide spraying and wasps that were introduced to kill the moth, Walter said.

Joe Napsha is a staff writer for Trib Total Media.

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