Our Forests
Forests in New York cover 18.6 million acres of land, making the state 61% forested. Whether it’s hiking, hunting, camping, or birdwatching, these forest lands provide recreational opportunities for millions of residents and visitors to the state’s scenic regions. New York’s forests also provide employment and bolster the state’s economy through the production of timber. New York’s forests are made of a variety of forest types with tree species such as maple, pine, oak, eastern hemlock, and more.
Invasive species threaten New York’s forests, damage our economy, and impact human health. Tracking, managing, and conducting research on invasive species and other forest health concerns is crucial for ensuring that New York’s forests remain a healthy, valuable resource for years to come.
Insects
Asian Longhorned Beetle
New York state has been managing Asian longhorned beetle (ALB) since the insect was first found in Brooklyn in 1996. Since then, ALB has been eradicated from all five New York City boroughs. The single remaining quarantine area is in Central Long Island, covering portions of Nassau and Suffolk counties. When ALB is found, infested trees are cut down and destroyed, while healthy nearby trees are sometimes treated to prevent future infestation. In January of 2024, USDA removed 10 square miles from the Long Island quarantine area, leaving 43 square miles under quarantine.
Hemlock Wooly Adelgid
Hemlock woolly adelgid (HWA) continues to cause widespread damage and mortality to eastern hemlock trees. In 2024, DEC treated hemlocks with systemic insecticides at Lake George Wild Forest, Glen Island Campground, Zoar Valley Unique Area, Carpenter Falls Unique Area, and multiple state forests to protect sensitive hemlock ecosystems and high public use areas. DEC supports HWA biological control work across the state, which uses the natural predators of invasive species to reduce their populations. In 2024, predators of HWA were released at more than 20 locations across New York, including silver flies and Laricobius beetles. It is hoped that chemical treatments will help to buy time for biological controls to become established and effective across the landscape.
Southern Pine Beetle
Southern pine beetle (SPB) continues to cause significant pine mortality on Long Island. Through an aerial survey in March 2024 followed by ground surveys, DEC mapped about 5,000 acres of damage on Long Island due to SPB. In 2024, DEC’s SPB program conducted thinning and prescribed fires to restore a healthy, naturally sparse pine barrens that is resistant to SPB outbreaks. In total, 250 acres of pine forest were thinned on DEC lands in Suffolk County. About 100 acres of dense scrub oak understory were mowed. DEC staff worked with land managers at Sarnoff State Forest to burn 250 piles of coarse woody debris and conduct 50 acres of woodland prescribed fires. Management activities were conducted outside the active season of the federally endangered northern long-eared bat in order to protect this sensitive species. At sites north of Long Island, DEC continues to trap for SPB to monitor potential spread of the beetle. To date, no established populations of SPB have been found in New York outside of Long Island.
Spongy Moth
Spongy moth outbreaks occur every 7 to 10 years and cause severe defoliation of oaks and other hardwoods. When populations get exceptionally high, moths will also feed on conifers like white pine and hemlock. Hardwoods can often recover from 1-2 years of defoliation, but may die if they are defoliated for multiple years in a row. Conifers do not rebound well, and may die after just 1-2 years of defoliation. The current outbreak began in 2020 in the Finger Lakes region and spread to many areas of the state, peaking in 2021. In 2024, the heaviest defoliation occurred in Columbia, Dutchess, Ulster, and Orange counties. Through aerial surveys, DEC mapped about 600,000 acres of defoliation in southeastern New York in 2024. Outbreaks typically collapse after 3 to 5 years, so we should be nearing the end of this outbreak.
Multiple years of defoliation due to spongy moth, combined with multiple years of drought, have led to observations of oak mortality in central and northeastern New York. These same factors are likely to impact oaks in the Hudson Valley area in the coming years. DEC will continue to monitor and further quantify the damage to oaks in 2025.
Emerald Ash Borer
Emerald ash borer (EAB) has expanded its range to nearly every corner of the state. In 2024, EAB was confirmed in Essex County for the first time. Research into biological control and surveys to locate potentially resistant ash trees are being conducted in all the infested regions of New York.
Red Pine Scale
Red pine scale, an invasive insect, was detected in Essex and Warren counties for the first time in 2024. Red pine scale nymphs feed on a red pine tree’s sap, eventually causing the tree to die. Infestations can be identified by the insects’ cocoons, which look like white, woolly masses around the base of red pine needles. Native to Japan, red pine scale was first detected in New York on Long Island in 1950. However, red pine scale had not been identified in upstate New York until 2024, possibly because colder temperatures kept populations low enough to remain undetected. In 2024, a significant amount of red pine in Essex and Warren counties that were surveyed for red pine scale showed signs of dieback, poor health, or mortality. DEC plans to conduct surveys in 2025 to determine the locations and abundance of red pine scale in New York.
Pathogens
Beech Leaf Disease
Beech leaf disease (BLD) was first found in New York in 2018 and has expanded rapidly across the state in the past few years. In 2024, BLD was confirmed in five new counties: Otsego, Oneida, Washington, Lewis, and Schenectady. Currently, there is no known treatment for BLD. Funded by the U.S. Forest Service, DEC is testing potential treatment strategies including canopy thinning and understory removal to see if the impacts of BLD can be mitigated by forest management.
Oak Wilt
Oak wilt is a disease that causes oak leaves to turn brown and fall off in spring and summer, typically killing the tree. Oak wilt is caused by a fungus and can spread when fungal spores are transported by beetles or when the roots of nearby oaks, especially red oaks, graft together with an infected tree. When oak wilt is detected in New York, a quarantine district is established to prohibit the movement of infected wood, preventing the disease from spreading. Quarantine districts currently exist in the towns of Middlesex, Bristol, South Bristol, Italy, and Glenville. In 2024, DEC conducted aerial surveys for oak wilt over previously known infected areas. No new cases of oak wilt were discovered.
Invasive Plants
Giant Hogweed
Giant hogweed plants have been managed by DEC since 2008 and are present in 48 counties in New York, with the largest and densest number of sites located in the western portion of the state. At sites where giant hogweed plants are found, a mix of manual and/or chemical control methods are used. Sites that have previously been treated for giant hogweed continue to be monitored until no giant hogweed plants are found for nine years, at which point they are considered eradicated. Information is available for landowners and the public through our giant hogweed information line, outreach materials, and website. Because of our control efforts, over 62% of historical giant hogweed sites in New York no longer have these invasive plants.
Kudzu
Kudzu plants have been managed by DEC since 2014 and are present in 14 southeastern counties in New York. Because of our control efforts, kudzu has been eradicated from over 30% of sites where it was historically present.
Forest Health Research Lab
The Forest Health Research Lab (FHRL) responded to 701 diagnostic requests and conducted four public site visits in 2024. Diagnostic requests and inquiries received by the FHRL came from across the state from the public, arborists/tree care professionals, foresters, and more. Additionally, the lab received inquiries from nine other states/provinces. General Invertebrate Identification (insects, spiders, mites, and worms) remains the most frequently inquired subject across the state for the second year in a row, followed by General Pathogen/Microorganism Identification (fungi, bacteria, slime molds, etc.). Many of these are native species that the public hasn’t seen before and would like identified.
Forest Health Research Lab staff looking for signs of beech bark disease. Photo credit: Erica Culbert
Public reports of invasive species are crucial to protecting the health of New York’s forests. The first detection of oak wilt in New York was reported by a concerned homeowner. Both HWA and BLD have been found at the edges of their known range by campers, hikers, and homeowners. Public reports also help us track outreach efforts and determine what issues are emerging across the state.
To report and invasive species, go to https://www.nyimapinvasives.org/report-an-invasive
