SCHENECTADY — The hemlock woolly adelgid, an invasive, aphid-like insect that attacks North American hemlock trees and has recently been found in several Capital Region locations — is now in Vale Cemetery.
Crews from the Davey Tree Expert Co. on Thursday chemically treated three infested trees in the cemetery. The hemlocks are expected to survive.
The bugs, in time, will not.
The insect ovisacs were spotted about a month ago, verified by Mary Werner, who chairs the invasive species committee of the Schenectady County Environmental Advisory Council.
Dr. Bernard McEvoy, vice president of Vale’s board of directors, first believed the trees would have to be cut down. Werner told McEvoy the trees could be treated and saved.
Read about efforts to treat other hemlock trees in this story.
The insects, native to Asia, are identified by the small white woolly masses that form on the underside of hemlock branches at the base of the needles. These masses — the ovisacs — can contain up to 200 eggs each. They can remain on the trees throughout the year.
Left untreated, the insects can kill hemlocks.
Michael Pollard, a sales arborist for Davey, said the adelgids — accidentally introduced to the United States in the 1920s — will feed on foliage by sucking juice through the needles.
“They’re not actually taking bites out of it,” he said, adding trees eventually start to lose their chlorophyll.
Once adelgids are established, hemlocks begin long declines.
“They start to look like zombies,” Pollard said. “They get really ugly looking. They’ll still hang on for a few years and just look terrible along the way. Eventually, they die.”
The infected Vale hemlocks are in the 19-grave Horsfall family plot, which dates to the 1800s. The most famous grave in the plot belongs to William Horsfall, who fought in the Civil War. Horsfall, a captain in the 18th New York infantry, was killed in the Battle of South Mountain near Burkettsville, Maryland, on Sept. 14, 1862.
Pollard estimated the hemlocks were planted when the Horsfall family began using the plot for burials. He estimated the trees, now around 80 feet tall, are all about 150 years old. Vale opened in 1857.
The Davey treatment pumped several gallons of the chemical compound imidacloprid — also sold under the trade name Merit — into soil near the root systems of the three hemlocks.
The chemical is toxic to the adelgids. Because it starts at the roots, it moves through the trunk and limbs slowly and can sometimes take a year to reach shoots in the top of a large tree. One application will protect the tree for at least four years.
The treatment cost Vale $540.
“They will overwinter and hatch new eggs,” Pollard said of the insects. “By controlling the crawlers, you break the cycle.”
Hemlock woolly adelgids first were seen in New York in 1985 and were first seen in the city of Schenectady in 2012. They also have been found recently at the Plotter Kill preserve in the town of Rotterdam, the Indian Kill preserve in the town of Glenville and in the town of Ballston, Saratoga County.
“It’s kind of patchy,” said Jason Benham, supervising forester in the Department of Environmental Conservation’s Bureau of Invasive Species and Ecosystem Health. “It’s not like a clean battle line. There are spots of it here and there; it’s been gradually expanding. We get reports on them fairly frequently.”
Adelgids can’t be compared to another insect pest that used to get publicity — leaf-devouring gypsy moth caterpillars. Benham said the caterpillars attack a broad host of trees and will stunt their growth. Unless a tree is defoliated two or three times in a row, Benham added, it will survive.
“With hemlock woolly adelgids, although there have been some cases where trees have survived much longer than expected, it seems to be pretty much 100 percent fatal in the Eastern U.S. on your hemlock trees, so far as we can tell,” Benham said. “We have not found or confirmed any sort of resistance to it.”
Werner believes the adelgids’ presence in Schenectady is another warning for the Adirondacks.
“We’re considered to be the gateway to the Adirondacks because there’s a contiguous forest up from the Catskills up to the Adirondacks, and it comes through Schenectady County,” Werner said. “There are no natural breaks … and hemlock stands are central to the character of the Adirondacks. If they kill them in the Adirondacks, it’s going to be very, very serious.”
According to the New York State Office of Parks, hemlocks are plentiful in Lake George, Keene Valley and much of the Lake Champlain Basin.
People are already looking for the hemlock killers. The bugs were found in the Adirondack Park last July — at Prospect Mountain in Lake George. The trees there were treated.
Neil Woodworth, executive director of the Adirondack Mountain Club, said the insects remain a large problem for the region. Adirondack groups are working with Cornell University to develop biological controls.
“White flies and beetles will prey on them; that’s our best hope for large areas,” Woodworth said. “A place like the Adirondacks, with billions of trees, you’re not going to be able to inoculate every tree.”
People with hemlocks on their property should look for tiny woolly masses about the size of a tiny cotton swab on the underside of branches, at the base of needles. Needle loss, branch dieback and and gray-tinted foliage are other clues.
People can email photos to the DEC at [email protected], for confirmation of infestation.