Gypsy moth caterpillar numbers down; spraying to begin

HARRISBURG, Pa. (WHTM) — Efforts to control an annual Pennsylvania pest are about to begin.

“We’re getting ready to go into the field. We’re monitoring egg hatch of the gypsy moth,” said Donald Eggen, chief of the Department of Conservation and Natural Resources Bureau of Forestry, Division of Forest Health.

Eggen says weather permitting, his agency’s gypsy moth suppression program will commence with the aerial spraying of pesticides within the next week or two.

“Game commission land, state forest lands, and state parks,” Eggen said. “We may identify areas where there are young stands of oaks in which we do not want to see a high level of mortality, areas that might contain trees that are about to be timbered.”

The gypsy moth caterpillar is not native to Pennsylvania. It is believed to have been introduced to the United States decades ago from overseas by someone wanting to breed the species with a native silk worm for use in the silk industry. The experiment failed and several of the gypsy moths escaped, gaining a foothold in nature, first in Massachusetts. The species is now believed to exist in at least 11 eastern states.

“Gypsy moth feed principally on oak trees, but they are known to feed on at least 250 other species of trees and plants,” Eggen said. “They will eat leaves at the point when the tree has pushed out its foliage to full development. If the tree is healthy, it will refoliate, which is good and bad. It needs the new leaves to photosynthesize, but now it has used up its reserve energy and the tree is now stressed. We get drought or other secondary diseases, and that’s how a lot of mortality of oaks occurs.”

This year, DCNR is scheduled to spray 46,000 acres of land, down significantly from 136,000 acres last year. While gypsy moth numbers appear to be in a down cycle for 2017, Eggen says the problem is still significant. The most deeply affected regions include northeastern Pennsylvania including Carbon, Luzerne, Lehigh and Northampton counties. Small portions of Cumberland, Dauphin, Juniata and Perry counties will also receive spraying. Private lands in three counties will also receive spraying.

Eggen says other species are often misidentified as the invasive gypsy moth. For instance, the eastern tent caterpillar, which spins a silky nest, mostly between the branches of fruit trees, is a much less destructive native species. While considered unsightly to property owners, Eggen says the small nests can typically be ignored or removed by hand, and most trees will grow back their leaves without affecting their health.

The DCNR will utilize four aircraft for its gypsy moth suppression program. Once spraying begins, two helicopters and two fixed-wing aircraft will operate from dusk to late morning or as weather permits until all areas are treated. Treatment areas will be posted on the DCNR Bureau of Forestry website.

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