\u201cYou can only collect the scion from them for grafting in the winter when the buds are entirely dormant,\u201d Rosenthal said. \u201cOtherwise, the grafting won\u2019t work.\u201d<\/p>\n
Earlier this week, MaMA arborists cut branches from two lingering black ash trees in Hemlock-Canadice State Forest, in the heart of the Finger Lakes. The scion will be sent to Cornell Botanical Gardens<\/a> where they\u2019ll be grafted onto rootstock.<\/p>\n The hope is scientists will one day unlock the mechanisms that allow lingering ash trees to tolerate infestation from the emerald ash borer, an invasive beetle from East Asia that has killed hundreds of millions of ash trees in the U.S. over the past three decades.<\/p>\n \u201cWe want to find these trees and propagate them to keep that genetic material in the environment from winking out,\u201d said Todd Bittner, director of natural areas for Cornell Botanic Gardens. \u201cThat\u2019s our particular role in the program\u2014we\u2019re essentially a gene conservation bank.\u201d<\/p>\n The collaboration between MaMA and Cornell is part of The Nature Conservancy\u2019s Trees in Peril<\/a> project, which seeks to restore ash trees on a landscape scale using EAB-resistant cultivars.<\/p>\n MaMA has so far identified more than 230 lingering ash trees. Most are from the Hudson Valley region, ground zero for the beetle\u2019s invasion of the Northeast, according to Rosenthal. The program has collected scion from 71 of these trees for use in Cornell\u2019s breeding program. <\/p>\n Bittner\u2019s goal is to have 50 to 60 genotypes or trees from different parents of three ash species\u2014white, black, and green\u2014in the ground, along with five clones from each of those parents as back up.<\/p>\n MaMA delivered the first batch of lingering ash cuttings to Cornell two years ago. The grafted trees were grown in pots until they were anywhere from three to seven feet tall. <\/p>\n In October, Cornell transplanted the first set of saplings from pots to a conservation bank in a natural area owned by the university. <\/p>\n In five years, the saplings will be big enough to provide scion for a new generation of ash trees that can be sent to other researchers for EAB resistance testing. <\/p>\n All told, it will take 15 to 20 years, from collection to propagation to field experiments, before scientists can begin to produce ash trees that might be able to withstand EAB\u2019s onslaught. <\/p>\n But the window for finding lingering ash trees is closing fast. Conservationists have only a year or two after EAB kills 95% of the ash trees in a particular area to collect scion from lingering ash. Right now, the Finger Lakes region is in that \u201csweet spot,\u201d said Bittner.<\/p>\n \u201cThe ash are really seriously declining in this region,\u201d Bittner said. \u201cMany places are reaching this 95% threshold or they\u2019re going to within a year or so. And we only have a couple years to find more lingering ash before those also succumb to the emerald ash borer.\u201d<\/p>\n Native to East Asia, EAB was first found in the U.S. in Michigan in 2002, though experts believe it likely hitched a ride a decade earlier on wood shipping crates from overseas. EAB has since spread to 37 states.<\/p>\n New York recorded its first case of EAB in Cattaraugus County in 2009. By 2014, it had arrived in Central New York. <\/p>\n Today, EAB has been confirmed in every NY county except Hamilton and Lewis, according to the state Department of Environmental Conservation.<\/p>\n Left to their own devices, EAB spread slowly. Adult beetles fly less than a half-mile from their host trees. But people unwittingly transport EAB long distances by hauling infected firewood and nursery stock. The same year EAB came to NY, DEC banned moving untreated firewood<\/a> more than 50 miles from its source. <\/p>\n Areas of NY most impacted by EAB infestation generally coincide with large population centers connected by major highways such as Buffalo, Rochester and Syracuse. But the bug\u2019s spread hasn\u2019t been uniform. <\/p>\n \u201cA lot of people think EAB has already killed off all the ash everywhere,\u201d Rosenthal said. \u201cActually, the distribution is like a patchwork quilt.\u201d<\/p>\n For instance, in areas like the Catskills where EAB has been present for a long time and there\u2019s very high ash mortality, it\u2019s still possible to find places untouched by EAB.<\/p>\n Signs of EAB infestation:<\/b><\/p>\n Adult EAB burrow into ash trees and lay eggs in the cambium beneath the bark. EAB larvae then chew their way through the cambium for about two years, leaving behind telltale tunnels that cut off the flow of nutrients between the tree\u2019s roots and upper canopy. <\/p>\n Most ash trees infested with EAB die within two to four years. Lingering ash are often surrounded by bare stands of dead and dying ash trees. <\/p>\n \u201cThey\u2019re kind of like the last man standing,\u201d Bittner said.<\/p>\n Lingering ash trees shouldn\u2019t be confused with trees that sprout in the aftermath of an EAB invasion, or trees growing in areas with less than 95% ash mortality. <\/p>\n To qualify as a lingering ash, trees must be chemically untreated, measure at least four inches in diameter at breast height, and retain healthy crowns. Most importantly, lingering ash are found only in areas with at least 95% ash mortality.<\/p>\n Scientists believe there are at least two mechanisms that make lingering ash trees more resistant to EAB. For one, lingering ash can wall off EAB larvae early in their life cycle, trapping them in a layer of cambium where they starve to death. <\/p>\n Another hypothesis is that lingering ash trees emit a different chemical signature that makes it more difficult for adult EAB to find them\u2014a kind of invisibility cloak.<\/p>\n But lingering ash trees are not completely immune to EAB. Even the hardiest specimens will eventually succumb to the EAB swarm. Finding the lone survivors is a race against time. <\/p>\n Conservationists want lingering ash from as many different areas as possible to maintain regional genetic diversity and to provide an insurance policy against future blights that might otherwise wipe out trees of a single cultivar or genotype.<\/p>\n \u201cWe want lingering ash source trees from New York to be planted in New York, and we want Ohio trees to be planted in Ohio,\u201d he said, \u201cpartly because they were adapted to those local conditions, those local soils, those local climates.\u201d<\/p>\n A high priority is given to black ash trees, which are far less common than white and green ash and \u201cdie much more quickly than the other two species when they\u2019re attacked by EAB,\u201d Rosenthal said. <\/p>\n Black ash typically grow in swampy areas and are critical in regulating complex wetland hydrology. Once EAB kills off all the black ash in a wetland, water levels rise and what was once a swamp can become a pond or a lake. <\/p>\n Furthermore, black ash hold great cultural significance for many Native American communities. <\/p>\n \u201cThey\u2019re used primarily for basketry and also for ceremonial purposes,\u201d Rosenthal said, \u201cand even feature very importantly in their language and so forth. So it\u2019s really crucial for them that black ash be conserved.\u201d<\/p>\n For a long time, EAB seemed unstoppable. The fate of ash trees appeared to be going the way of the American chestnut, a majestic tree that once dominated the landscape east of the Mississippi River<\/a>. But the discovery of lingering ash changed all that.<\/p>\n \u201cPeople were hopeless. And when they\u2019re hopeless, they don\u2019t do anything,\u201d Rosenthal said. \u201cBut when we started finding lingering trees, people were like, \u2018Oh, they\u2019re real!\u2019 It\u2019s a game changer because it gives people hope, and if they have hope, they take action.\u201d<\/p>\n Here are two ways you can take action to help save ash trees from annihilation. All you need is smartphone and a little bit of naturalist training.<\/p>\n Cornell Botanical Gardens recommends using the TreeSnap<\/a> app to document locations of lingering ash using your smartphone. With a tap of your finger you can virtually tag trees in the wild on a digital map for follow up by scientists.<\/p>\n![\"Cornell](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/01\/TRM6VSJPR5AZ3GTN2S4ROK4HYM.jpg\")
A lingering white ash tree in NY’s Hudson Valley, surrounded by dead ash trees. Scientists are racing to find lingering ash trees before emerald ash borers wipe them all out. Lingering ash trees hold the key to creating future strains of ash trees that are highly resistant to EAB.Radka WildovaA patchwork quilt of dead trees<\/p>\n\n
![\"Cornell](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/01\/LAGJ3FOPE5FSRGEIGAOXGLT76I.jpg\")
In this triptych, a white ash tree located in Clark Reservation State Park shows evidence of damage from emerald ash borers, including S-shaped galleries in the cambium (left), and D-shaped exit holes in the bark (right). An EAB larva is shown in the middle photo.Mike ServissLast man standing<\/p>\n![\"Cornell](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/01\/A7LADT24ABFY3FCSSVU3PMT5FU.jpg\")
Emerald ash borer beetle shown next to a penny on a piece of an infested ash tree. Serpentine patterns on the bark are created by EAB larvae as they feed under the bark. Michael Mancuso | For NJ.com.TT TT Michael MancusoBlack ash a priority<\/p>\n![\"Cornell](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/01\/RMSOHPHJ7ZF6VGJ4XE5JZMQGNA.jpg\")
This map from the Monitoring and Managing Ash project shows levels of ash tree mortality due to EAB infestation in areas across the Northeast. Lingering ash trees are found in areas with at least 95% mortality (red or green on the map).MaMACitizen science<\/p>\n