Wednesday, February 1st, 2023
Wednesday, February 1st, 2023

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In New York, invasive insect reaches Adirondacks

Hemlock needles have two white lines on the undersides. (New York State Department of Environmental Conservation)

A minor infestation of the hemlock woolly adelgid (Adelges tsugae) was confirmed on forest preserve lands in the town of Lake George in Warren County on July 18, the New York State Department of Environmental Conservation (DEC) announced Thursday, July 27. This is the first known infestation of the invasive in the Adirondacks.

HWA, a tiny insect from East Asia first discovered in New York in 1985, attacks forest and ornamental hemlock trees. 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 10 years of infestation in the insect’s northern range.

A small cluster of early stage HWA was detected on one branch of an old-growth Eastern hemlock tree on Prospect Mountain during a field trip by a senior ecologist from the Harvard Research Forest.

DEC immediately dispatched a HWA survey crew to the site and was joined by staff from Cornell University’s New York State Hemlock Initiative. HWA was located and confirmed on a number of branches on the tree by a Cornell scientist and later by DEC’s DEC Diagnostic Lab. The mature tree had no visible sign of crown thinning.

The crews spent 72 hours surveying 250 acres of forest and found only one other tree, a small Eastern hemlock near the original infested tree, that contained one branch with a small cluster of early stage HWA.

While this is the first recorded infestation of the invasive, exotic pest in the Adirondacks, it previously has been detected in 29 other counties in New York, primarily in the lower Hudson Valley and, more recently, in the Finger Lakes region. Seventeen other states along the Appalachian Mountain range from Maine to Georgia also have HWA infestations. HWA is a listed prohibited species under DEC’s invasive species regulations.

DEC is evaluating means to eradicate this infestation and prevent it from spreading. This will not include cutting down trees, which is not an effective means for controlling HWA as it is with other invasive forest pests.

The most effective treatment method for control of HWA is the use of insecticides. The insecticide is applied to the bark near the base of the hemlock tree and are absorbed and spread through the tissue of the tree. When HWA attaches itself to tree to feed, it receives a dose of the pesticide and is killed.

Damage from the insect has led to widespread hemlock mortality throughout the Appalachian Mountains and the southern Catskill Mountains with considerable ecological damage, as well as economic and aesthetic losses. HWA infestations can be most noticeably detected by the small, white, woolly masses produced by the insects that are attached to the underside of the twig, near the base of the needles.

Eastern hemlock trees, which comprise approximately 10 percent of the Adirondack forest, are among the oldest trees in New York with some reaching ages of more than 700 years. They typically occupy steep, shaded, north-facing slopes and stream banks where few other trees are successful. The trees help maintain erosion control and water quality, and the hemlock’s shade cool waters providing critical habitat for many of New York’s freshwater fish, including native brook trout.

Survey efforts by DEC and Cornell’s New York State Hemlock Initiative will continue to determine if other infestations are present in the surrounding area. As the closest known infestation of HWA is 40 miles away in Schenectady County, DEC is asking hikers, campers, boaters, sportsmen, and others recreating on or along forestlands in northern Schenectady, Saratoga, and southern Warren counties to check Eastern Hemlock trees and report any HWA infestations.

More information on HWA, including identification, control techniques, and reporting possible infestations can be found at Cornell’s New York State Hemlock Initiative or DEC’s website. You may also call DEC’s toll-free Forest Pest Information Line at 1-866-640-0652 to ask questions and report possible infestations.

— New York State Department of Environmental Conservation

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