The secretary noted weather conditions curtailed "heavy infestations" anticipated in northeastern and central counties in spring 2016, and reduced last year's statewide defoliation to 104,018 acres.
"Conversely, warm dry weather in April and May, 2015, helped delay emergence of a fungus -- a natural and most effective enemy of the gypsy moth -- until June and the result was nearly 700,000 acres of defoliation in 2015," Dunn said.
The gypsy moth suppression program is conducted by the Bureau of Forestry on a request basis, with the goal of preventing defoliation so that trees do not become stressed and succumb to disease and other pests.
A 46,540-acre suppression program in 110 treatment blocks is proposed for 2017 in 12 counties. They are: Carbon, Columbia, Cumberland, Juniata, Lackawanna, Lehigh, Luzerne, Mifflin, Northampton, Perry, Snyder and Union.
In spring 2016, a total of 352 blocks totaling more than 136,000 acres were sprayed in 21 counties.
Aerial spraying by helicopter and fixed-wing airplanes principally will be on state-managed forests, game lands and federal lands (Francis E. Walter Dam), as well as residential county lands in three participating counties. Lackawanna, Lehigh and Northampton counties have requested bureau spraying on a cost-share basis.
Though weather dependent, spraying is expected to begin in late April or early May, and be completed by the end of May or early June.
Maps of the treatment areas will be posted on the DCNR Bureau of Forestry website: http://www.dcnr.state.pa.us/forestry/insectsdisease/gypsymoth/index.htm
Targeted sites are determined by surveys of egg masses and other indicators across the state indicating gypsy moth populations are increasing and have the potential to cause major defoliation.
In 2015, gypsy moth populations increased in eastern Pennsylvania after several years of high populations in the northwestern part of the state. Two years ago, DCNR treated 26,433 acres in six northeastern counties.
Bureau of Forestry experts note the state's oak stands are especially vulnerable to gypsy moth infestation, often resulting in tree mortality. The loss of habitat, timber and tree growth are considerable when gypsy moth populations go untreated.
Biological in nature, the applied insecticide must be ingested by young caterpillars as they feed on emerging foliage.
"Private woodland owners and public lands visitors must remember spraying is a suppression effort and a forest management effort to protect trees from moderate to severe defoliation," said Dr. Donald Eggen, the bureau's forest health manager. "The gypsy moth will continue its cyclic population with ups and downs about every five to 10 years. We cannot eradicate the insect in Pennsylvania, only try to minimize the damage in areas where the land manager requests assistance. It's too well-established and is here to stay."
Forestry bureau experts identify the gypsy moth as one of the most destructive forest pests in Pennsylvania. Feeding while in the larval -- or caterpillar -- stage, the insect usually hatches and begins feeding from mid- to late April in southern Pennsylvania, and in early to mid-May in the northern part of the state.
Oak, apple, sweet gum, basswood, birch, aspen and willow trees are affected the most by the gypsy moth. Older larvae also will feed on hemlock, pines, spruces, northern white cedar and other conifers. A tree begins to significantly suffer when 30 percent or more of its leaf surface is lost.
Begun in 1972, forest insect spray program is a cooperative effort among DCNR's Bureau of Forestry, county governments and the U.S. Department of Agriculture Forest Service's Forest Health Protection Unit.
The gypsy moth was introduced to North America in 1869 at Medford, Mass., where it was used in a failed silk-production experiment. The gypsy moth first reached Pennsylvania in Luzerne County in 1932, and since then has infested every county.
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SOURCE Pennsylvania Department of Conservation and Natural Resources