Invasive hemlock bug found in Oswego County

Hemlock Woolly Adelgid, seen above infecting a tree, have been found in Oswego County.

OSWEGO COUNTY — Scientists recently observed three separate populations of hemlock woolly adelgid (HWA) in southwest Oswego County, and urge residents and land managers to keep an eye out for signs of the invasive forest pest.

The hemlock woolly adelgid, or HWA, is an invasive, aphid-like insect that attacks North American hemlocks. According to the state Department of Environmental Conservation (DEC), HWA are very small (1.5 mm) and often hard to see, but they can be easily identified by the white woolly masses they form on the underside of branches at the base of the needles. Juvenile HWA, known as "crawlers," search for suitable sites on the host tree, usually at the base of the needles. They insert their long mouthparts and begin feeding on the tree’s stored starches. HWA remain in the same spot for the rest of their lives, continually feeding and developing into adults. Their feeding severely damages the canopy of the host tree by disrupting the flow of nutrients to its twigs and needles. Tree health declines, and mortality usually occurs within four to 10 years. All species of hemlock are vulnerable to attack, DEC officials said.

While conducting early detection searches for hemlock woolly adelgid (HWA) over the past several weeks, members the SLELO PRISM (St. Lawrence Eastern Lake Ontario Partnership for Regional Invasive Species Management) Early Detection Team, Robert Smith and Brittney Rogers, made the first confirmed observations of HWA within the SLELO PRISM region. The region encompasses Oneida, Oswego, Jefferson, Lewis and St. Lawrence counties. SLELO PRISM is collaborating with the DEC, Oswego County Soil and Water Conservation District, affiliated land managers and the New York State Hemlock Initiative to develop a strategic response to provide guidance and assistance to the landowners and managers of the infested sites.

A delimiting survey was conducted at the initial site by SLELO PRISM staff, the Oswego County Soil and Water Conservation District, the Youth Bureau, the park land manager and numerous volunteers. At the 40-acre site, more than 1,100 hemlocks were surveyed with roughly 30 percent visibly infested. This population has likely been established for several years due to tree stem mortality. More surveys are being planned in collaboration with the DEC and SLELO partners.

Experts have suggested that the more likely area for HWA to spread in the SLELO region is along the eastern Lake Ontario shoreline because of the moderated temperatures adjacent to the lake.

For those participating in hemlock woolly adelgid survey efforts, hemlock stands located along the eastern Lake Ontario shoreline should take survey priority. Landowners and land managers in Oswego county and throughout the eastern Lake Ontario region are encouraged to check their hemlock trees for signs of hemlock woolly adelgid.

Signs to look for include: lack of bright green foliage on the tips of hemlock branches in the spring, needle-loss and dead branches in the top portion of hemlock trees, and the presence of white woolly masses in addition to black insects with white fringe, both of which will be nestled along hemlock branches where the needles connect to twigs.

If HWA is found on your property, you are under no obligation to treat the trees, however, treatment is encouraged for two reasons; first, hemlock trees provide essential services that are vital to forest health; and second, treatment will reduce the rate of spread of this invasive forest pest into other parts of the region. Treatment may include a combination of insecticides and biological controls. You can learn about HWA treatment options at the state Hemlock Initiative’s website: www.nyshemlockinitiative

If you think you have found HWA in the SLELO region, be sure to note the location of the observation, take clear photos of the infestation and email the information to the SLELO PRISM Terrestrial Coordinator, Robert Smith at or contact the NYS DEC Forest Pest Hotline at 1-866-640-0652 or report the observation via

To get involved in surveying for HWA in the SLELO region, join the invasive species Volunteer Surveillance Network at

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