Emerald ash borer now in every corner of Adirondack Park; killing 7% of New York’s trees

NYS DEC confirming reports of infestations in every county in the Adirondacks; Champlain Valley hit particularly hard

By Tim Rowland

The emerald ash borer, once a distant threat, is now believed to be in every Adirondack county, inevitably dooming a species of tree that represents 7% of the New York forest and is valued for baseball bats, indigenous woven baskets, canoe components, wildlife habitat and fall foliage.

“At the beginning of this year, only two counties in New York did not have confirmed emerald ash borer (EAB) infestations (Lewis, Hamilton), and DEC is currently working to confirm credible reports in both of those counties,” said the NYS Department of Environmental Conservation, in a response to questions about the invasive insect. “At the continental scale, EAB is present coast to coast. This does not mean that every ash tree or stand in the state is already infested, but there is no geography that is free of EAB.”

Rapid spread across the region

Over the past year, the emerald ash borer has swept south through Clinton County, leaving highly visible stands of dead trees as far south as Peru and Valcour on Lake Champlain.

Meanwhile, iNaturalist maps of reported sightings show heavy infestation in Warren County and creeping up the Champlain Valley from the south as far as Crown Point.

“EAB is on the move in the Adirondacks with pest populations building and moving into the Adirondack interior from several directions, especially from the southeast, northeast, and northwest,” said Ari Giller-Leinwohl, Adirondack Park Invasive Plant Program terrestrial invasive species manager. “We are seeing the damage in the form of canopy dieback, epicormic growth, flaking bark/blonding, galleries in the cambium layer, D shaped exit holes, and adult EAB are being caught in APIPP and partner-agency green funnel traps.”

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The advancement of the ash borer is variable, said the DEC, and can be predicted on human activity, such as the transport of firewood. In the Adirondacks, ash can run as high as 20% to 30% in some areas, according to the DEC. The population in the Adirondack Park itself is heaviest in riparian areas beside streams, but in the uplands represents only 1% to 2% of the canopy, the relative isolation itself giving some measure of protection.Left to its own devices, the infestation can travel up to a dozen miles a year Giller-Leinwohl said, and unlike many other threats, it doesn’t simply weaken the tree over time. “It’s not this death by a thousand cuts that you get from, say, the nematode that causes the beech leaf disease,” he said. “The issue with emerald ash borer is very fast tree mortality.”

Ash trees fill important ecological role

Ash is not as dominant a species as the American chestnut — wiped out a century ago by blight — but it is a complementary fixture in the Adirondack forest: white ash in upland elevation, and black and purple ash in wetlands and river valleys.

At Point au Roche State Park along Lake Champlain, site manager Charles L. Payson IV estimated that between 20% to 30% of the forest is, or was, ash. Many of those trees are gone, while others have been protected or bypassed by the insect.

“We have definitely been called upon to respond to these ash trees that have died and are over-top of trails or have dead branches that lean over roadways,” he said. “We have had a contractor come in and treat some of the ash trees on the beach side with insecticide, and these particular trees have been tagged with metal tags at their bases.”

Payson said the larger trees were killed, while some of the smaller-in-diameter ash have survived so far.

Biological control efforts underway

The park has also been active in the introduction of parasitic wasps that feed on EAB larvae. These wasps, said the DEC, have been released at dozens of sites and have become well-established in several  locations.

Kristin Collins, environmental educator at the Point au Roche Nature Center, said there have been three releases of wasps at the park beginning in 2020. Samples have been taken to see if colonies have been established and are awaiting analysis.

“Most of the infested trees are already dead or dying at this point, but we’ll see what happens in the future,” Collins said.

There is enough initial evidence for some hope, not for the mature ash of today, but for the next generation of ash saplings. Establishing wasp colonies in the Adirondacks “is a heavy lift, and it certainly is not going to stop emerald ash borer in its tracks, but I think it’s a program that, if you can further amplify it, certainly could keep populations (of EAB) down,” Giller-Leinwohl said.

Limited options for property owners

For property owners concerned about their ash trees, there are some limited options. A favored specimen or a handful of woodlot seed trees can be protected with insecticide, but the treatment costs depend on the size of the tree and can run several hundred dollars. The treatment must be repeated every two years.

The DEC and APIPP do not recommend preemptive cutting of ash, unless it’s for safety reasons.

“Leaving some ash untouched helps DEC to identify the small percentage of ash trees that show some resistance to EAB (called ‘lingering ash’) and may also provide the beneficial parasitoids the chance to thrive or occupy new areas,” the agency said.

Forest succession and climate change

Conservationists are also watching to see what trees and shrubs move in to take the place of the ash, particularly in wet, low-lying areas. Native species including hackberry, river birch and hornbeam are likely candidates, although there is always the risk that invasives like buckthorn and honeysuckle will get there first.

As the climate warms, it’s also possible that a more southern-oriented bottomland tree such as sycamore could move into lower elevations. 

As demoralizing as the loss of ash‚ a beautiful tree, with compound leaves and tight, diamond-shaped bark, might be, the combination of biological control, potential resistance to the insect in some trees and upland isolation give some hope that the ash won’t join the chestnut as a memory in eastern hardwood forests.  “I don’t think that those bugs are smart enough to get every last tree,” Giller-Leinwohl said.

Top: Dead and dying ash trees in Clinton County. Photo by Bruce Rowland