State to treat hemlocks for invasive pest in Saratoga, Warren counties

New hemlock woolly adelgid infestation found near Spruce Mountain trail

By Gwendolyn Craig

The state plans to treat infestations of invasive hemlock woolly adelgid in the Adirondacks this fall including a new batch found in the Wilcox Lake Wild Forest in Saratoga County.

That wild forest invasion discovered at the beginning of this year and a previously reported population on the western side of Lake George in Warren County demand chemical attention, said the state Department of Environmental Conservation (DEC).

The Saratoga County population is the second known infestation of the bug, outside of the Lake George area, in the 6-million-acre Adirondack Park. Approximately 10% of the park’s trees are hemlocks.

There are at least six Eastern hemlock trees near the Spruce Mountain Fire Tower in the town of Corinth that have the aphid insects, according to the DEC. It’s not clear how long the bugs have been there, though the DEC said the infestation is light and there is no tree mortality. 

A volunteer with the Adirondack Park Invasive Plant Program spotted the Saratoga County infestation and reported it to iMapInvasives, an online mapping system that allows the public to post potential invasive species sightings. 

The DEC plans to treat about 40 acres of forest preserve hemlock trees in Saratoga County and about 40 acres in Warren County by spraying and injecting pesticides called imidacloprid and dinotefuran. The untreated Warren County infestation is at the Hearthstone Campground in the town of Lake George. The adelgid is more widespread there and the DEC plans to treat “numerous” infested trees. The DEC will post warning signs at the sites and along nearby trails, according to work plans. 

The DEC hopes to apply pesticides before the end of November, but is currently accepting public comments on the work plans. Comments should be made by Oct. 18 to Jason Denham, NYSDEC Division of Lands and Forests, 625 Broadway, Albany, NY 12233 or [email protected]. 

Hemlock woolly adelgid are native to Japan and were first spotted in the Adirondacks in 2017 on the village of Lake George’s Prospect Mountain. In 2020, a camper discovered a new infestation on the eastern shore of Lake George. Surveys have ramped up since, uncovering proliferation all along the eastern shore, on several of the lake’s islands and at the DEC’s Hearthstone Campground on the western shore.

Adelgids are so small they can spread on the wind. All hemlock woolly adelgids are females and reproduce asexually. They colonize hemlock branches. Adults suck on the twigs, indirectly killing the tree’s buds. During the winter, the adelgids cover themselves in a white, waxy wool beneath branches. An infested tree will die in four to 10 years.

The New York State Hemlock Initiative, a Cornell University program that receives state funding, is rearing bugs that are predators to the adelgid. These biological controls have been released on Lake George. They will not be released at the Saratoga County site, the DEC said, as they are not effective for small populations of adelgids. The biological controls need enough prey to survive. Biological controls were released this spring at the Hearthstone Campground site, the DEC said in its work plan, “and is being monitored for establishment.”