DRESDEN — Marked and sprayed, an estimated 2,500 Adirondack hemlock trees were treated last month after the second known infestation of the invasive hemlock woolly adelgid was reported in the region this summer.

The state Department of Environmental Conservation and its partners completed the first round of insecticide treatment in a multi-year effort to control the spread of the sesame-seed-sized insect.

The DEC dispatched a forest health specialist in early August to survey trees on state forest preserve lands in Washington County, after a camper at a Glen Island area campsite reported a tree through the iMapInvasives mobile app. The specialist located “one heavily infested and two lightly infested” Eastern hemlock trees near the campsite along the northeastern portion of Lake George, some 30 miles away from the closest known HWA presence in southern Saratoga County.

Staff from DEC, Cornell’s New York State Hemlock Initiative, the Adirondack Park Invasive Plant Program and Lake George Land Conservancy conducted additional surveys along 16.3 miles of Lake George shoreline, identifying 250 acres of affected forest with infested trees on the shore of the Shelving Rock Special Management Area, at the Buck Mountain Trailhead and on Dome Island.

Led by DEC’s Division of Lands and Forests, a three-week treatment period began Oct. 6, primarily covering 138 high-priority acres.

The treatment plan, which was developed in September, involved spray applications of the short-acting dinotefuran, a common insect pest control chemical, and imidacloprid, a type of neurotoxin for long-term protection. Applied to the base bark of infected trees to limit impacts on non-target species, the insecticides are the most effective widespread treatment for HWA control, according to the DEC.

About 80 trees, in areas determined to be “sensitive” by partners, were treated by direct injection of insecticides to further reduce impacts on the watershed and non-target species. Biological control was also implemented, with 620 Laricobius beetles released within the infested area through a partnership between the DEC and state Hemlock Initiative. The adelgid-feeding beetles have been used as a biological control for HWA for more than a decade in the United States.

Invasive species treatment is budgeted through DEC and the state Environmental Protection Fund, and a new research agreement, finalized this year between DEC, Cornell University and the New York Invasive Species Research Institute, totals $3.5 million in the state EPF. The five-year agreement includes $2.5 million for invasive species projects, and the remaining $1 million is set to be allocated over two years through the Hemlock Initiative.

Native to East Asia, HWA damages hemlocks by feeding on tree tissue and nutrients through a thin, tubed mouthpiece. The wounds inflicted by the mouthpiece lead the tree to heal over the twigs, causing the twig tissue to become clogged from the healing attempt. The clogs then prevent effective water and nutrient flow to the ends of the twigs, and new growth — through new needle growth — cannot continue, and the tree eventually starves.

First recorded in New York in the 1980s, scientists believe HWA likely arrived in the state on nursery stock trees sold near New York City. By 2008, HWA had been discovered in the Finger Lakes region, as well as metropolitan areas, including Syracuse, Rochester and Buffalo.

HWA was previously recorded in the Adirondacks at Prospect Mountain in 2017, at the southern end of Lake George in Warren County, and has since been eradicated there.

The DEC reports HWA has been detected in 47 counties, mostly in the lower Hudson Valley and the Finger Lakes regions, with 17 other states from Maine to Georgia along the Appalachian Mountains having confirmed infestations.

Eastern hemlocks and Carolina hemlocks are most susceptible to widespread damage from HWA, and the two North American species are the only known hemlock species in the world to be “at risk for fatal HWA infestations,” the state Hemlock Initiative reports.

The Adirondack forest is comprised of about 10% Eastern hemlock trees, according to the DEC, with some individuals hundreds of years old and providers of crucial shade habitat and erosion control along stream banks.

The DEC, Hemlock Initiative and a statewide network of hemlock and invasive species groups encourages reporting of suspected HWA sightings through iMapInvasives, a free mobile app for photographing and reporting invasive species locations. Suspected sightings can also be reported directly to one of the state’s eight DEC Partnerships for Regional Invasive Species Management, or PRISMs.

To spot HWA, the Hemlock Initiative advises people to look at the base of hemlock needles, where the needles meet the twig. At the needle base, HWA will exhibit characteristic, white woolly masses from mid-fall through spring, and in summer, HWA will appear as black sesame seeds with a thin ring of white around them.

More information and HWA identification techniques are posted to the state Hemlock Initiative’s website. To report possible infestations, call the DEC forest pest information line at 1-866-640-0652, or download the iMapInvasives app.

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