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DCNR to Begin Spraying Forests in Spongy Moth Suppression Effort


​Harrisburg, PA -- Department of Conservation and Natural Resources (DCNR) Secretary Cindy Adams Dunn today announced the start of aerial spraying of state woodlands to combat spongy moth (Lymantria dispar dispar, formerly known as the gypsy moth) populations poised for spring outbreaks in many sections of Pennsylvania.

“Suppression efforts are commencing now as these insects emerge and begin feeding,” Dunn said. “As the statewide leader in protecting our Commonwealth’s natural resources, we are conducting aerial spraying to keep this invasive pest in check and protect the trees from defoliation to maintain Pennsylvania’s 2.2 million acres of state forests.”

In 2022, spongy moth defoliated 855,406 acres in Pennsylvania.

DCNR’s Bureau of Forestry will oversee spraying of 274 sites totaling 290,753 acres. Included will be portions of 13 state forests and 18 state parks, in 19 counties located in southcentral, central, northcentral, and northeast Pennsylvania.

The agency’s spraying efforts will cost more than $6 million, using a combination of General Funds, DCNR Special Funds, and Federal Funds.

In 2022, a total of 209,000 acres were treated. In addition to DCNR’s spray program, the Pennsylvania Game Commission will also be conducting an aerial spray program in 2023 on approximately 109,000 acres of State Game Lands.

State parks to be sprayed include:

  • Bald Eagle, Centre County
  • Black Moshannon, Centre County
  • Colton Point, Tioga County
  • Fowler Hollow, Perry County
  • Hyner Run, Clinton County
  • Hyner View, Clinton County
  • Kettle Creek, Clinton County
  • Kings Gap, Cumberland
  • Leonard Harrison, Tioga County
  • Little Pine, Lycoming County
  • Ole Bull, Potter County
  • Pine Grove Furnace, Cumberland County
  • Poe Paddy, Centre County
  • Poe Valley, Centre County
  • Promised Land, Pike County 
  • R.B. Winter, Union County
  • Ravensburg, Clinton County
  • Sinnemahoning, Cameron County

“In Pennsylvania, these destructive, invasive insects go through cycles where outbreaks generally occur every five to 10 years,” DCNR Forest Health Manager Rosa Yoo said. “Populations had declined in 2019 and 2020 thanks to the spongy moth fungus disease and wet spring weather, but that no longer is the case in 2021 and 2022, resulting in the need for suppression efforts.”

The suppression program is conducted with the goal of minimizing defoliation so that trees do not become stressed and succumb to disease, other insect pests, or drought. Aerial spraying will be conducted by one helicopter and seven fixed-wing aircraft.  Progress of the spray program can be followed using the interactive map on the DCNR web page, which shows the location of all 274 spray blocks.

Targeted sites are determined by surveys of egg masses and other indicators across the state indicating populations are increasing and have the potential to cause major defoliation.

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 most affected by the spongy moth.

Bureau of Forestry experts note the state’s oak stands are especially vulnerable to infestations, often resulting in tree mortality. The loss of habitat, timber, and tree growth are considerable when populations go untreated

 A tree begins to significantly suffer when 30 percent or more of its leaf surface is lost.

The applied insecticides, tebufenozide or Bacillus thuringiensis subsp. kurstaki, must be ingested by young caterpillars as they feed on emerging foliage.

These products are subject to State and Federal environmental review and are deemed safe for use and are commonly used in agriculture.

Launched in 1972, the forest insect spray program is a cooperative effort among DCNR and the USDA Forest Service's Forest Health Protection Unit.

The Lymantria dispar dispar was introduced to North America in 1869 at Medford, Mass., where it was used in a failed silk-production experiment. The spongy moth first reached Pennsylvania in Luzerne County in 1932, and since then has infested every county.

Visit DCNR’s website for more information on spongy moth spraying.

Check out DCNR’s Calendar of Events for events on public lands.

MEDIA CONTACT: Wesley Robinson, 717-877-6315

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