GOWANDA — The fight to protect hemlock trees in remote areas of Zoar Valley from the invasive hemlock woolly adelgid (HWA) is just getting underway.
Earlier this week, state Department of Environmental Conservation foresters, rangers and certified pesticide specialists located and treated hundreds of hemlock trees on both sides of the South Branch of Cattaraugus Creek in the Forty area of the town of Persia.
The white, wax-like hemlock woolly adelgid, an aphid-like pest, attaches itself to the hemlock needles and sucks nutrients from the tree, killing it in five to 10 years.
A hemlock with HWA was spotted by a Cornell University scientist in the adjacent Deer Lick Preserve, owned by The Nature Society, in September. That sparked a wider survey of hemlock trees in the area, according to DEC forester David Paradowski, and two more trees were found in the same area across the South Branch in the Zoar Valley Multiple Use Area.
Zoar Valley and Chautauqua Gorge are two Western New York gorges with significant numbers of hemlock trees, Mr. Paradowski said in an interview Friday. Foresters looked along streambanks where HWA has been found in the past along the Hudson River in eastern New York and in Pennsylvania. It was also discovered earlier this year in two locations in Allegany State Park.
The hemlock on The Nature Conservancy’s side of the South Branch had been uprooted but was still alive, Mr. Paradowski said. Dinotefuran and imidacloprid were applied by DEC-certified pesticide applicators directly to the bark of the tree, where it will absorb into the vascular tissue. It was also sprayed on about 200 surrounding hemlock trees.
The two flagged trees on the west side of the creek where HWA was confirmed were cut down and burned, he said. About 400 surrounding hemlock trees were thoroughly sprayed with the chemicals.
Dinotefuran moves rapidly through the tree, killing any adelgids that are feeding on it, while imidacloprid moves more slowly, protecting the tree from further attacks for five years or more, according to DEC officials.
The DEC employees had to carry the chemicals and spray tanks up the South Branch for more than a half-mile, crossing the creek several times, Mr. Paradowski said. Those applying the chemicals sprayed the tree trunks from a level of four feet down to the ground.
“It soaks into the tree,” he said. “It is water-soluble and gets taken up to the rest of the tree.”
Many of the trees that were sprayed not because HWA had been confirmed, but because they were in the same general area and were accessible on the often steep slopes in the gorge. Many hemlock branches are too high to see from the ground, Mr. Paradowski said.
Trees along waterways are often the victim of HWA because they are an open pathway for birds, Mr. Paradowski said. A bird perching on a hemlock branch can pick up some of the HWA on its claws and deposit it on the next hemlock tree it perches in. The white, waxy insects can blow off in a light wind.
“There are thousands of hemlock trees in the area,” Mr. Paradowski said. “Many are not accessible due to their location. There are many more areas we’d like to survey.” Some of those areas are along Cattaraugus Creek. While winter is a good time to be looking for HWA, it can be dangerous walking around in the gorge in certain conditions.
Mr. Paradowski said it is believed the HWA infestation in the Deer Lick and above the Forty area is at least two years old.
“Last winter killed off a lot of them, but not all,” he said.
The hemlock woolly adelgid is not real tolerant of extreme cold like the region experienced last winter.
“The cold weather slowed it down,” Mr. Paradowski said.
“We’re not going to be able to save all the hemlocks with chemicals. We’ll treat some of the trees that can be easily reached, but we’re hoping predators will be able to provide a balance.”
Predator beetles from the Pacific Northwest have been proven effective against the HWA in other locations, he said.
DEC employees and others are currently looking for nearby areas to rear the predator beetles. Hemlock hedges with low-lying branches that are infested with HWA would be ideal. The beetles would feed on the hemlock woolly adelgid and then be collected and released in other areas of hemlock infestation.
Area volunteers have been vital to finding outbreaks of HWA, Mr. Paradowski said. While they are not a particularly valuable tree for timber, hemlocks are important because they provide habitat for a wide variety of wildlife and provide shade to cool streams for fish.
(Contact reporter Rick Miller at firstname.lastname@example.org. Follow him on Twitter, @RMillerOTH)