Lingering ash and the emerald ash borer in Ohio

At a glance

Overview

The emerald ash borer, a metallic green beetle from northeast Asia, was confirmed in Ohio at Whitehouse, in Lucas County, on February 28, 2003. Ohio cut more than 30,000 trees trying to stop it, then gave up eradication in 2006 for lack of money, and by 2016 the beetle was in all 88 counties. The state's big forest ash are about 84 percent gone, and Columbus alone had cut more than 12,000 ash from city land by 2014. Yet in the dead woods along Swan Creek a Forest Service team noticed a healthy ash in 2009, and such "lingering ash" became the parents of a breeding program whose first offspring were scheduled for test plantings in 2026.

The name

The beetle is Agrilus planipennis, and when it was identified in July 2002 it was so little known that, as Ohio State noted in October 2003, it had not had a common name two years earlier. Forest Service scientists defined "lingering ash" in 2012 as healthy ash in areas infested for several years where the vast majority of ash have been dead for a few years. The name was meant to be cautious but hopeful; geneticist Jennifer Koch told a public radio program it is like the last person to leave a party, who just lingers.

Stories

A beetle without a name

Beetles collected from dying ash near Detroit reached Michigan State University in June 2002 and were conclusively identified on July 9, 2002, by Eduard Jendek. Tree-ring cores later showed ash dying from the borer in southeast Michigan as early as 1997, so it was probably established by the early to mid-1990s. The U.S. Department of Agriculture's plant health service says it "is thought" to have arrived in solid wood packing material from Asia in the early 1990s. Its native range runs from eastern Russia and northeastern China to Mongolia, Taiwan, Japan and Korea. Females lay roughly 50 to 100 eggs, and the larvae feed under the bark until the adults chew out through D-shaped holes an eighth of an inch wide. In green ash, the larvae kill more than 99 percent of the trees they infest.

Woodpeckers at Whitehouse

At Whitehouse, woodpeckers had flaked the bark off infested ash while feeding on the larvae, and inspectors found D-shaped exit holes, winding larval galleries and vertical bark splits. About 200 ash were infested there, and to wipe the beetle out the Ohio Department of Agriculture destroyed about 4,000 trees before May 1, 2003, the infested trees plus a quarter-mile buffer. Ohio State entomologist Dan Herms said that fall he feared the new finds were "just a preview of things to come". Michigan authorities then counted more than 5 million ash dead or dying around Detroit.

It came in on trucks

In August 2003 a nursery owner at Hicksville, in Defiance County, reported suspicious damage, and inspectors found about 100 infested trees in Defiance County and one in Paulding County; about 20 infested trees at Rossford in Wood County had come from a Michigan nursery, and 15 infested landscape trees in Columbus had been bought from one. Ohio State reported that the outlying finds were traced to ash logs and nursery stock brought in from Michigan in the previous few years. People were not the only carriers: the same year preliminary flight-mill tests at Ohio State suggested the beetle might fly at least 10 kilometers. By the end of 2003 the beetle had been found in five Ohio counties.

Cutting a firebreak, and running out of money

In 2004 the state went further, removing all ash within a half-mile of four infestation sites; more than 30,000 trees were cut, chipped and burned. New finds kept turning up in 2005 and 2006, some inside the cleared areas, and eradication was suspended in 2006 for lack of funding. The state's forest-health reports of those years repeated a projection that the beetle could cause more than $3 billion in damage to Ohio's economy over 10 years. By 2007 an estimated 53 million ash had been killed in Michigan, Ohio and Indiana combined.

County by county to 88

The Ohio Department of Agriculture's survey had the beetle in 26 counties by the end of 2006, in a band from northwest Ohio east to Cleveland and south to Columbus, and that year the federal plant health service put all of Ohio under its quarantine. The count reached 35 after 2007 and 39 after 2008, with the infested counties following Interstates 80/90 and 75 and U.S. 23. After the 2009 trapping season 53 of Ohio's 88 counties were under state quarantine, and in 2010 the department made its quarantine statewide. Known infestations then climbed to 72 counties in 2013, 80 in 2014 and 85 in 2015. In 2016 the last two, Adams and Vinton counties, were confirmed, completing all 88.

The quarantine ends

The plant health service's final rule, published December 15, 2020, ended the federal domestic quarantine effective January 14, 2021, and the money went instead to biological control. As of March 2026 the service listed the beetle in 36 states, the District of Columbia and six Canadian provinces. Ohio's own statewide rule dated from 2010; the published record gives no clear date for when the state retired it, and states remain free to regulate ash wood and firewood on their own.

Six years from healthy to dead

In Ohio plots, ash stands went from healthy to almost complete death of the mature trees within about six years. At 60 sites set up from 2005 to 2008, with more than 3,000 ash followed, the share dead by 2019 was 98.6 percent of white ash, 95.8 percent of green, 91.8 percent of black, 66.7 percent of pumpkin and 28.3 percent of blue ash. Trap catches rose slowly, then exponentially, peaked when about half a site's ash had died, then crashed. Dead trees did not stand long: of 1,100 Ohio ash that died from 2006 to 2014, 20 percent had fallen within two years and more than 80 percent within eight.

Ohio's ash ledger

On Ohio forest land, where the Forest Service's inventory counts trees (city trees are not in it), live ash at least 5 inches thick fell from about 71.2 million in 2004 to 21.2 million in 2022 and 11.5 million in 2024, and their share of Ohio's trees that size fell from 8.0 to 1.5 percent. Standing dead ash that size rose from about 8.2 million in 2004 to 42.1 million in 2022, about a third of all standing dead trees of that size in the state. Ash timber volume fell from about 1.10 billion cubic feet to about 156 million, a drop of 86 percent. The Ohio Department of Natural Resources' 2020 assessment put ash mortality at 86 million cubic feet a year, 10 percent of ash volume annually and up 614 percent from 2008. Counting every stem at least an inch thick, Ohio's forests held about 260.6 million live ash in 2004, a peak of 294.8 million in 2010 and 141.7 million in 2024.

The cities' bill

In 2007 Columbus city forester Jack Lowe oversaw about 120,000 street trees, roughly 10 percent of them ash, and said treating 12,000 trees would probably not be cost-effective. By May 2013 Columbus crews had removed nearly 9,000 trees, and by June 2014 the city had taken out more than 12,000 of an estimated 30,000 ash on golf courses, parks and other city land, spending about $4 million with $4.6 million more expected. In Worthington, more than 200 of the city's 435 ash were removed, while insecticide treatments helped the rest survive. Upper Arlington began cutting ash before the beetle arrived, in 2006, and by 2020 had removed 850 street ash and replanted 800 trees at a cost of $493,550 over 15 years. Cleveland reported that 2,206 ash had been removed and replaced citywide since 2013. In May 2020 Dayton announced that all remaining ash in the public right of way would be systematically removed.

What ash gave Ohio

Ohio nurseries sold more than $2 million of ash at wholesale in 1998 and held a standing crop worth more than $20 million. The wood is strong and shock-resistant, second only to hickory for tool handles, and the Forest Service counts Louisville Slugger bats and Fender and Taylor guitars among the products made from white and green ash. Ash was the leading wood for Major League bats for a century.

Swan Creek: one creek, one count

On the floodplain of Swan Creek inside Oak Openings Preserve Metropark, near Toledo, where ash had been the most common tree, Forest Service scientists counted, in 20 survey plots, 858 standing dead green ash and 53 live ones, and they estimated about 11,595 dead ash within 50 meters of a 10-kilometer stretch of creek. Their 2010 survey of that stretch found 299 living ash, 2.5 percent of the trees that had been there, and only 111, under 1 percent, with healthy crowns. About half of those healthy trees showed no sign of the beetle at all, and a year later 74 percent of them were still healthy. A later Forest Service slide gives slightly different figures, 284 live and 108 healthy, so "about 1 percent" is the safe way to say it.

The tree spotted on the walk out

Forest Service ecologist Kathleen Knight had measured a forest of hundreds of healthy ash in 2006 and came back in 2009 to find them dead. On the walk out after a day measuring dead trees, she told a public radio program, an intern crossing a bridge pointed at a green tree and asked if it was an ash. It was, and it was the first lingering ash her team found. Koch said the idea ran against the scientific mantra of the time: no co-evolution, no resistance.

Breeding from survivors in Delaware, Ohio

The Forest Service's ash program has two arms: crossing resistant Asian ash with native ash, modeled on the American chestnut program, and selecting rare resistant native trees. In common gardens at Delaware and Wooster, Manchurian ash from the beetle's home range survived best, most North American species and cultivars died, and blue ash was the best native survivor. To be tested, a lingering tree must be forest-grown, have a healthy crown, be big enough to have been attacked at the peak, and still be alive at least two years after more than 95 percent of nearby ash died. Some lingering green ash were less favored by feeding adults, one killed more larvae and another raised lighter larvae, so more than one defense is at work.

Partial, not immune

Three lingering green ash used as parents killed only 28, 6 and 10 percent of the larvae in tests, yet their offspring killed significantly more larvae than offspring of ordinary green ash. Koch's 2024 summary put it this way: not all lingering ash are resistant, but all resistant trees are lingering ash, about half of them by lab test. A 2026 study of 51 lingering green and white ash selected from 2008 to 2013 in southeast Michigan and northwest and central Ohio found that 54 percent of the white and 78 percent of the green selections beat the average unselected tree at killing larvae. The first improved seed orchards use lingering-by-lingering seedlings suited to eastern Ohio, southern Michigan and western Indiana.

Seeds in the bank

From 2021 to 2023 the Great Lakes Basin Forest Health Collaborative, run from Holden Forests and Gardens in Kirtland, logged 115 new lingering ash reports and about 451,000 seeds from 94 trees in the 2022 mast year, including trees on Cleveland Metroparks and Toledo Metroparks land, and expanded a 2-acre research orchard at Kirtland. Its 2024 report said green and white ash from southern Michigan and Ohio were confirmed to pass the resistance trait to their offspring, with progeny to be planted in 2026. The Ohio Division of Forestry joined surveys for lingering ash in 2023, 2024 and 2025 and found healthy trees in several counties.

Blue ash, and a town named for it

In the monitoring plots more than 70 percent of blue ash were alive in 2019, while under 5 percent of white and green ash were; where they grew together, white ash died first and blue ash declined later. Feeding and landing studies show adult beetles prefer other ash over blue ash. The forest inventory agrees: big white ash fell from 52.1 million to 7.0 million between 2004 and 2024, while blue ash stayed roughly flat at about 1.1 million. The Hamilton County city of Blue Ash says it took its name from the Carpenter's Run Baptist Church of 1797 to 1828, "built of logs from the blue ash tree".

A borer in the fringetree

In late 2014 a Wright State University biologist found the beetle completing its life cycle in white fringetree, an olive-family tree, in the Dayton area: 4 of 20 mature ornamental fringetrees showed symptoms, and one held at least three generations of larvae. Later lab work showed it could develop in cultivated olive as well.

Wasps from the beetle's homeland

Three parasitic wasps from China were first approved for release in 2007, and a fourth from the Russian Far East in 2015; by 2023 they had been released in more than 360 counties in 31 states. Ohio was a release state from the start, with long-term monitoring sites set up in 2008 and wasps released at Ohio sites that June and August. The federal rearing center in Brighton, Michigan, has released more than 9 million wasps since 2009 in 34 states, Ohio among them, and in some early-release regions they have spread and pushed the beetle down to low densities.

The second wave

Trap counts in northwest Ohio have shown a small resurgence in recent years, and in January 2025 Knight said the Forest Service was seeing a second outbreak killing younger surviving ash, "bringing a lot of mortality". At Seymour Nature Preserve in Delaware, she showed a reporter a large ash recently killed in the second wave. Because the beetle does not attack roots, killed ash can send up sprouts, and many Ohio woods hold an "orphaned cohort" of ash seedlings left behind by the dead canopy. The Ohio Division of Forestry's Thomas Macy said ash will probably persist, but "ash borers are here to stay" and it will not likely be a dominant canopy tree again.

How to report a survivor

Forest Service scientists use the free TreeSnap app to find and verify newly reported lingering ash; as Knight put it, there are not enough scientists to survey every forest. The collaborative's Lingering Ash Report Form asks for a forest-grown, untreated ash over 4 inches thick with a healthy canopy, in a county where more than 95 percent of other ash have died, plus GPS, photos and 10 nearby ash. The Forest Service's older "Submit a Survivor Ash" page asks for a natural tree over 10 inches thick, never treated, with no dead upper branches, where over 90 percent of large ash died at least two years ago.

Myths and the record

• "Ohio had 3.8 billion ash trees." An Ohio State fact sheet says a Forest Service study found more than 3.8 billion white ash in Ohio. The Forest Service's plot inventory counts about 4.15 billion live trees of all species at least an inch thick in Ohio forests in 2004, of which ash were 6.3 percent.
• "The borer reached Ohio in 2002." Ohio's forest-health reports said "discovered in 2002" for years, then corrected it to 2003 in the 2024 and 2025 editions; 2002 is the Michigan year.
• "Lingering ash are immune." The breeding program's goal is partial resistance with genetic diversity, not immunity, and the state's 2020 assessment notes a tree's survival could be due to chance or to being unattractive for egg-laying.
• "Ash is gone from Ohio." About 141.7 million live ash stems still stood in Ohio forests in 2024, mostly small, though the Forest Service cites an international listing of green, white, black, blue and pumpkin ash as critically endangered.
• "A firebreak of cut ash will stop it." Ohio tried twice, and new finds kept appearing, some in cleared areas; in the plots, ash also died faster, not slower, where there were fewer ash.
• "Small ash are safe." Knight wrote in 2014 that it attacks ash as small as an inch thick, and the second wave is killing the younger survivors.

Timeline

• 2002: On July 9 beetles from dying ash near Detroit are identified as Agrilus planipennis. (source)
• 2003: On February 28 the borer is confirmed at Whitehouse, Lucas County; about 4,000 trees are destroyed before May 1. (source)
• 2003: Later finds are traced to Michigan logs and nursery stock; five counties are infested by year's end. (source)
• 2004: All ash within a half-mile of four sites, more than 30,000 trees, are cut, chipped and burned. (source)
• 2006: The beetle is in 26 counties and the federal quarantine covers all of Ohio. (source)
• 2007: The first parasitic wasps from China are approved for release. (source)
• 2009: The first lingering ash is spotted at Oak Openings Preserve Metropark. (source)
• 2010: The Ohio Department of Agriculture makes its quarantine statewide. (source)
• 2014: Columbus has removed more than 12,000 ash from city land. (source)
• 2016: Adams and Vinton counties are confirmed, and all 88 Ohio counties are infested. (source)
• 2019: In Ohio plots 98.6 percent of white ash and 28.3 percent of blue ash are dead. (source)
• 2021: The federal quarantine ends on January 14. (source)
• 2022: About 451,000 seeds are gathered from 94 lingering ash in a mast year. (source)
• 2024: Live ash 5 inches and up are down to about 11.5 million, 84 percent below 2004. (source)
• 2025: Knight reports a second wave of the borer killing younger ash. (source)
• 2026: A study of 51 lingering selections is published, and progeny test plantings are scheduled. (source)

Sources

• research.fs.usda.gov: Poland and McCullough, Emerald ash borer: invasion of the urban forest (2006)
• research.fs.usda.gov: Siegert et al., dendrochronological reconstruction of early spread (2014)
• aphis.usda.gov: EAB biological control release and recovery guidelines (2026)
• archive-news.cfaes.osu.edu: Ohio State researchers conduct key studies on destructive ash pest (2003)
• fs.usda.gov: Ohio Forest Health Highlights 2003
• fs.usda.gov: Ohio Forest Health Highlights 2005
• fs.usda.gov: Ohio Forest Health Highlights 2006
• fs.usda.gov: Ohio Forest Health Highlights 2008
• fs.usda.gov: Ohio Forest Health Highlights 2009
• fs.usda.gov: Ohio Forest Health Highlights 2011
• fs.usda.gov: Ohio Forest Health Highlights 2013
• fs.usda.gov: Ohio Forest Health Highlights 2014
• fs.usda.gov: Ohio Forest Health Highlights 2015
• fs.usda.gov: Ohio Forest Health Highlights 2016
• fs.usda.gov: Ohio Forest Health Highlights 2024
• fs.usda.gov: Ohio Forest Health Highlights 2025
• dontmovefirewood.org: federal deregulation of emerald ash borer (2020)
• apps.fs.usda.gov: Forest Inventory and Analysis, Ohio live trees 1 inch and up
• apps.fs.usda.gov: Forest Inventory and Analysis, Ohio growing-stock trees 5 inches and up
• dam.assets.ohio.gov: Ohio Forest Resource Assessment (2020)
• research.fs.usda.gov: ash mortality in Ohio monitoring plots (2023)
• nrs.fs.usda.gov: Knight et al., factors affecting ash mortality (2013)
• research.fs.usda.gov: Knight et al., lingering ash at Oak Openings (2012)
• alleghenyfront.org: lingering ash in Ohio (2024)
• thereportingproject.org: the emerald ash borer hasn't won yet (2025)
• dontmovefirewood.org: Koch, ash resistance breeding slides (2024)
• frontiersin.org: progeny of lingering green ash (2023)
• research.fs.usda.gov: Mason et al., New Forests (2026)
• research.fs.usda.gov: ash breeding plan (2012)
• research.fs.usda.gov: Koch et al., lingering green ash bioassays (2015)
• research.fs.usda.gov: Knight, ash monitoring (2014)
• research.fs.usda.gov: biological control releases, 2007-2009 (2010)
• research.fs.usda.gov: Kovacs et al., cost of EAB on developed land (2010)
• fs.usda.gov: Hermes et al., ash common gardens (2015)
• fs.usda.gov: Duan et al., EAB biocontrol (2023)
• fs.usda.gov: Submit a survivor ash
• fs.usda.gov: Fire Effects Information System, white ash
• holdenfg.org: Great Lakes Basin Forest Health Collaborative annual report (2023)
• holdenfg.org: Great Lakes Basin Forest Health Collaborative partners report (2024)
• holdenfg.org: Lingering Ash Report Form (2021)
• woodlandstewards.osu.edu: What is the emerald ash borer?
• corescholar.libraries.wright.edu: Cipollini, white fringetree as a host (2015)
• etd.ohiolink.edu: Klooster, ash regeneration after EAB (2012)
• blueash.com: history of Blue Ash
• wosu.org: Columbus, Grandview Heights plan for emerald ash borer (2007)
• wcbe.org: Columbus fighting ash borer (2013)
• wcbe.org: city continues battle with tree-killing beetle (2014)
• vtcommunityforestry.org: EAB municipal management case study, Upper Arlington
• news5cleveland.com: Ohio City neighborhood fights to save ash trees
• patch.com: Dayton to remove ash trees in right-of-way areas (2020)