Department of Environmental Conservation

D E C banner

For Release: Tuesday, August 28, 2012

DEC Confirms First Discovery of Hemlock Woolly Adelgid in Schenectady County

The Hemlock Woolly Adelgid (Adelges tsugae) was confirmed for the first time in Schenectady County on August 20, the New York State Department of Environmental Conservation (DEC) announced today. A private homeowner in the City of Schenectady reported a suspected infestation to the USDA Forest Service. The infestation was later confirmed by DEC Forest Health staff.

This is the first record of this invasive, exotic pest in Schenectady County, which has been detected in 28 other counties in New York. Previously, Hemlock Woolly Adelgid (HWA) had been found primarily in the lower Hudson Valley and, more recently, in the Finger Lakes region. Seventeen other states along the Appalachian Mountain range also have HWA infestations, from Maine to Georgia.

HWA is a tiny insect from East Asia that attacks forest and ornamental hemlock trees which was first discovered in New York in 1985. It feeds on young twigs, causing needles to dry out and drop prematurely and causing branch dieback. Hemlock decline and mortality typically occur within four to ten years of infestation in the insect's northern range. Damage from the insect has led to widespread hemlock decline, high levels of hemlock mortality in forests and considerable ecological damage as well as economic and aesthetic losses. HWA infestations can be most noticeably detected by the small, white, woolly masses that are attached to the underside of the twig, near the base of the needles.

Hemlock trees are among the oldest trees in New York with some reaching ages of more than 700 years. They typically occupy the steep slopes and stream banks where few other trees are successful, which helps maintain erosion control and water quality. The hemlock's shade provides the cool water critical to the habitat of many of New York's freshwater fish.

This invasive exotic insect is continuing to spread north within the natural range of hemlock. HWA was detected in Albany county several years ago and in Schoharie County in 2011. The DEC Forest Health program conducts annual surveys for HWA, funded by a grant from the U.S. Forest Service (USFS). This new discovery is believed to be part of a natural progression of the insect's expanding range, rather than an outlier.

Cultural, regulatory, chemical and biological controls can reduce the HWA's rate of spread and protect individual trees. There are several options for homeowners and woodlot owners to manage hemlocks infested with HWA, including:

  • Reducing hemlock tree stress by watering during drought periods and pruning dead and dying limbs and branches;
  • Avoiding the use of nitrogen fertilizers on infested hemlocks as it will actually enhance HWA survival and reproduction;
  • Being cautious while moving plants, logs and mulch from infested to un-infested areas, particularly when HWA eggs and crawlers are present from March through June;
  • Moving bird feeders away from hemlocks and removing isolated infested trees from a woodlot may also help prevent further infestations;
  • Spraying hemlock foliage with properly labeled horticultural oils and insecticidal soaps on trees that are small enough to be saturated;
  • Systemic insecticides may be an option for larger trees. These insecticides must be applied around the base of the tree or injected into the trunk, making this treatment limited to individual trees in readily accessible, non-environmentally sensitive areas and is less feasible on a broad scale in natural areas. Chemical treatments also only offer a short-term solution and applications may need to be repeated annually. For insecticide guidelines for New York, see Cornell University's Crop and Pest Management Guidelines, and consult a certified pesticide applicator;
  • Woodlot Management and harvesting options will differ depending on the particular forest and the management goals. Unless timber revenue is the main objective, preemptive cutting of uninfested hemlocks is not recommended, as cutting could remove potentially resistant hemlock. Woodlot owners should seek advice from a DEC forester by calling the hotline number listed below.

Biological control opportunities using natural enemies, such as predators and pathogens, from the adelgid's native environment may be the best option for managing HWA in forested settings. The U.S. Forest Service, in partnership with USDA Animal Plant Health Inspection Service (APHIS), DEC, Cornell University and other universities, has been researching and introducing several predators known to feed exclusively on adelgids, which are slowly becoming established throughout the infested region. Efforts to locate, evaluate and establish other natural enemies to better control HWA populations continue.

Dispersal and movement of HWA occur primarily during the first life stage ("crawler") as a result of wind and animals that come in contact with the sticky egg sacks and crawlers. Isolated infestations and long-distance movement of hemlock woolly adelgid, most often occur as the result of people transporting infested nursery stock or other forest products.

Many states, including Vermont, New Hampshire, Maine Ohio, Michigan and Wisconsin, have HWA quarantines that address import and movement of hemlock nursery stock and forest products into their states to prevent the spread of HWA. All state quarantines offer a compliance agreement option for nurseries or forest industries wanting to import hemlock forest products from infested counties. These states require State phytosanitary certificates obtained from the NYS Department of Agriculture and Markets for import of hemlocks from HWA-infested counties in New York.

More information on HWA can be found at the New York Invasive Species Clearinghouse. For questions or to report possible infestations, call DEC's toll-free Forest Pest Hotline at 1-866-640-0652.

  • Contact for this Page
  • Press Office - Lori Severino
    625 Broadway
    Albany, NY 12233-1016
    email us
  • This Page Covers
  • Page applies to Region 4