Hemlock Woolly Adelgid, or HWA, as the invasive aphid-like insect is called, has been found in a stand of eastern hemlocks on Forest Preserve lands on the eastern shore of Lake George, the state’s Department of Environmental Conservation announced August 11.
So far as anyone knows, it is only the second infestation of HWA to have reached the Adirondack Park. A small cluster of HWA was discovered in three hemlocks on Prospect Mountain in July, 2017. Those trees, however, were successfully treated with pesticides and declared pest-free earlier this year.
Last week, according to the Department of Environmental Conservation, a camper using iMapInvasives, a digital early detection mapping system that allows citizen scientists, educators and natural resource professionals to report invasive species locations, alerted the agency to an infestation north of Shelving Rock.
“That it was detected at all was pretty near a miracle,” said Dr. Mark Whitmore, the forest entomologist leading the Cornell University-based New York State Hemlock initiative.
Whitmore was on Lake George last week assisting DEC teams survey the extent of the infestation.
Impacts of HWA on Lake George Forests
If allowed to spread, HWA would have significant ecological, aesthetic and economic consequences for the Lake George watershed, said Whitmore, who noted that hemlock is among the most important species of tree found in the southeastern sections of the Adirondack Park.
“You can’t but be impressed by how common hemlocks are on the shores of Lake George; if it’s not the most commonly found tree here, it’s right up there,” said Whitmore.
The loss of Lake George’s hemlocks to HWA would create a visual blight, Monica Dore, the Lake George Land Conservancy’s Conservation Manager, noted in an earlier interview with the Lake George Mirror.
“It would be pretty horrifying,” she said. “HWA leaves a tree looking lifeless, grey, drained of color; it looks like something that would fall apart if you shook it,” she said.
HWA feeds on young twigs, causing needles to dry, drop prematurely and causing branches to die. Hemlock decline and mortality typically occur within four to ten years of infestation, said Dore.
But both Dore and Alex Novik, the Conservancy’s Land Steward, have stressed the hemlocks’ ecological value in presentations on terrestrial invasive species.
“The hemlocks’ needles contain nutrients; they shade streams and cool waters for wildlife, they provide habitat for birds, they stabilize soils and protect water quality. HWA may initially attack trees, but the ultimate fall-out from their introduction and transmission is much more wide-spread,” said Novik.
DEC: Effective Treatment from Pesticides
According to the DEC, an initial survey of the Lake George shoreline found three infested hemlocks near the campsite.
“If the infestation is limited, it will be manageable, if we move rapidly,” said Whitmore.
But, Whitmore emphasized, “We have just begun the survey process. We have yet to check on the islands and the interior of the eastern shore. This will take a few weeks.”
A thorough survey, ascertaining the size and extent of the infestation, will enable an inter-agency group and its advisors to determine the best method of managing the infestation, the DEC stated.
According to the DEC, insecticides, applied to bark near the base of the tree and absorbed through its tissue, remain the most effective method for controlling HWA.
In addition to the hemlocks on Prospect Mountain, chemicals have been used by both the DEC and the Office of Parks, Recreation and Historic Preservation to control the spread of HWA at a number of sites, state parks included, the DEC said.
Cornell Lab Rearing Natural Predators
The DEC, in conjunction with the New York Hemlock Initiative, is also promoting the use of biological controls, or natural predators, to suppress HWA populations and ensure the survival of eastern hemlock populations.
In November, 2017, the DEC announced that it had contributed $500,000 toward the creation of a $1.2 million laboratory at Cornell University to research and breed insects naturally inclined to prey upon HWA.
“We’ve learned a lot about implementing HWA biocontrols over the past few years and it reaffirms my belief that we are moving in the right direction,” said Mark Whitmore, who leads the lab.
“We’re not just growing bugs,” he said. “We’re researching the system within which the predator interacts with the prey so that any release will be efficient and effective.”
Whitmore added, “We hope that these predators or perhaps others we may identify will have a widespread impact on HWA and offer long-term survival for eastern hemlock populations.”
Researchers are currently focusing their attention on three insects, said Whitmore.
A beetle from the Pacific Northwest, one of the HWA’s predators, has been released from the lab and established itself in a number of locations in upstate New York.
Two species of Silver Fly have been released and found to have been able survive upstate New York winters.
Current experiments seek to determine if the flies can survive at higher elevations.
According to Mark Whitmore, the goal of the new lab is to develop and release predator species throughout New York capable of controlling HWA populations.
“Creating an effective, biological control program is not a simple process and will take years but we are moving as fast as possible,” said Whitmore.
“Naturally, people want to see results, but it takes patience. This is not a short-term fix,” he said.
“Bio-controls represent a long-term sustainable option because after a number of years, pesticides cease to be an economical or ecologically prudent choice. With pesticides, we can only treat individual trees. Bio-controls are scaled to the landscape,” said Charlotte Malmborg, an education and outreach coordinator for the New York State Hemlock Initiative. “The predators released are not confined to a single tree. Once established, the population grows and spreads beyond the original point of introduction.”
LGLC, DEC, Monitoring for HWA
Even after the predators have successfully established themselves, monitoring of the watershed’s forests, stream corridors, wetlands and shorelines, by the Lake George Land Conservancy, the DEC and others is expected to continue.
“As a land trust, we protect lands from threats of all kinds, including HWA,” said Jamie Brown. “We want to work with every not-for-profit group and municipality in the area to get the word out about this invasive’s potential impacts.”
According to the DEC, climate change contributes to the dispersal of Hemlock Wooly Adelgid and the growing size of local populations.