HARRISBURG, PA — The Pennsylvania Department of Conservation and Natural Resources (DCNR) began its annual aerial spraying initiative on Monday, May 5, to suppress the spread of spongy moth populations that pose a significant threat to the state’s forests. This year’s program targets 74,779 acres of critical forestland, a substantial reduction from the 227,000 acres treated the year prior and the 595,324 acres defoliated in 2024.
“Pennsylvania’s forests are one of the Commonwealth’s most valuable natural assets, providing clean air and water, recreation opportunities, and a sustainable timber resource,” said State Forester Seth Cassell. “Each year, spongy moths pose a significant threat to our native oak forests, and DCNR works to target and suppress outbreaks to prevent widespread tree loss. This reduction is a strong indication that our suppression efforts are making a difference, and we remain committed to protecting these vital forested landscapes.”
Spongy moth larvae, known for their voracious feeding habits, primarily attack oak, apple, birch, willow, and other tree species, starting in mid-April in the southern regions of the state and early May farther north. Unchecked infestations can strip trees of their foliage, leaving them vulnerable to disease, pests, and environmental stressors like drought.
Scope of the 2025 Program
This year’s effort focuses on 65 sites across 13 counties, including areas within five state forests and seven state parks. Regions targeted for spraying include Tiadaghton State Forest in Clinton and Lycoming counties, Delaware State Forest in Pike and Monroe counties, and Kings Gap State Park in Cumberland County, among others. DCNR will also collaborate with the Pennsylvania Game Commission, which will spray an additional 38,000 acres of State Game Lands.
Forest Health Manager Rosa Yoo emphasized the importance of this work in maintaining the ecological integrity of Pennsylvania’s forests. “Spongy moth populations in Pennsylvania appear to be declining, particularly in the central part of the state, thanks to ongoing suppression efforts and the natural end of the insect’s outbreak cycle,” Yoo stated. “That said, we’re still seeing hotspots and lingering populations that will be addressed in this year’s suppression program.”
While spongy moth numbers show an overall decrease, northeastern Pennsylvania remains a concern due to clustering identified during egg mass surveys conducted last fall and winter. Spray operations will address these vulnerable areas, supporting a statewide trend toward population reduction.
Environmentally Safe Approach
The aerial spraying program uses targeted insecticides, specifically tebufenozide and Bacillus thuringiensis subsp. kurstaki. These products, harmless to non-target species such as bees, must be ingested by young caterpillars to be effective. Both insecticides undergo rigorous environmental review and are widely used in agriculture for pest control. Spraying will be carried out by two helicopters and two fixed-wing aircraft, with application sites identified through egg mass counts and other monitoring metrics.
Tree health is a central focus of DCNR’s strategy. A tree begins to suffer when more than 30% of its foliage is lost. Sustained defoliation over two to three years can result in tree mortality, a devastating outcome for Pennsylvania’s oak-dominated forests that affects wildlife habitats, timber resources, and the ecosystem’s carbon capture capabilities.
Additional Measures Targeting Threatened Areas
Simultaneously, DCNR will spray parts of Somerset, Fayette, and Westmoreland counties to combat Fall Cankerworm infestations, another defoliator that has compounded pressure on forests stressed by repeated pest attacks and drought conditions. Although native to the region, excessive cankerworm activity could further hinder forest recovery, prompting this preventative action.
A Holistic Commitment to Forest Health
The suppression efforts come as part of Pennsylvania’s wider commitment to managing forest health and preserving its natural resources. Oaks, a critical tree species in the state, provide essential habitats and food sources for insects and wildlife. Protecting these vital trees ensures the sustainability of Pennsylvania’s forests—which, along with supporting biodiversity, play a key role in recreation and the economy.
Looking ahead, DCNR will continue monitoring insect populations and prioritizing proactive measures to mitigate potential infestations. Forested landscapes across the state stand to benefit not only from this year’s efforts but from ongoing management aimed at safeguarding these invaluable resources for generations to come.
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