Battle of the Ash Borer

Matthew Miller’s story about scientists’ efforts to slow the spread of the emerald ash borer won a AAAS Kavli Science Journalism Award in 2015. Miller is currently the Lansing State Journal’s storytelling coach. 

‘The devastation was complete’

Tom Yack steered his black SUV past the blue-and-electric-purple walls of the Skatin’ Station II and swung south toward the industrial buildings that line Ronda Drive. To the east, the 1.1 million-square-foot W. F. Whelan Co. warehouse that used to be a Kmart distribution center. Along the road, companies that make up much of Canton Township’s small manufacturing base: Champagne Grinding & Manufacturing Co. and Directional Regulated Systems, Inc. and a dozen others.

“This is old industrial,” Yack said, as he slowed the car. “This could be the area.”

He has lived in the township since 1971, when it still touted itself as the “Sweet Corn Capital of Michigan.” The slogan wouldn’t stick. A never-realized plan to integrate the Detroit public schools through cross-district busing created a housing boom. The Plymouth-Canton schools lay just outside the “desegregation area.” By the time Yack became township supervisor in 1988, its population had quadrupled and cornfields were being replanted with new houses at a rate of 1,000 units a year.

Yack was acting as a guide, offering his best guess about a point of entry, the epicenter of the invasion, the place where the emerald ash borer, the most costly and destructive forest insect ever to gnaw its way across the North American continent, first arrived from other shores.

Earlier this year, researchers from Michigan State University published the results of a meticulous effort to determine where and when the borer arrived and how it spread. They divided Michigan’s southeastern corner into a grid, searching in each square for the longest dead or longest infested green ash tree. They collected core samples from 1,085 trees, used the thin tree rings of drought years and thick rings of abundant years to establish dates.

The emerald ash borer probably arrived in the early 1990s, they found, possibly as early as the late 1980s. Larvae were likely carried along inside of wooden packing materials from the borer’s native range in China.

Of those 1,085 trees, the one that fell victim to the ash borer the earliest was in Canton Township, a stroke of cosmic drollery, maybe. In the 1830s, enthusiastic about burgeoning trade with China, Michigan’s state legislature named three townships after Chinese cities. Only in Canton did the name stick.

When developers built on Canton’s farmland, they had to plant trees or pay into a tree fund. The township planted ash trees along its major roads.

“A great street tree,” Yack said. “It was resistant to salt. It could do OK in drought periods. We mono-planted.”

“And the devastation was complete,” he said, “just complete.”

The ash borer has wiped out virtually every ash tree in southeast Michigan. In much of the rest of the state’s lower peninsula, there are few trees left to fight for.

But, in a sense, this is still one of the front lines in the fight against an insect that has laid waste to more than 100 million ash trees from Massachusetts to Colorado and has another 8 billion or so waiting for it.

Scientists here were the first to recognize the emerald ash borer as a threat. They gave the metallic green beetle a name in English. Some have spent the past dozen years chipping away at the puzzle of how to stop an insect that is singularly lethal to its hosts and uncommonly difficult to track.

They have lost most every battle. They may yet win the war.

Mystery of a dying ash

Ash yellows is a disease caused by a parasitic bacteria, spread by leafhoppers and spittlebugs, capable of killing a weak tree in as little as year. It was also the best guess of arborists called upon back in the early 2000s to explain why the ash trees in western Wayne County were dying.

That was Dave Roberts’ initial diagnosis, but the MSU plant pathologist had doubts.

In June of 2001, an arborist named Guerin Wilkinson asked Roberts to come out to Bradbury Parkhomes, a condominium development in Plymouth. Every ash on the grounds was in decline.

Bradbury Parkhomes is less than a mile down Joy Road from Canton Township’s industrial district.

The sickness didn’t look like ash yellows, Roberts recalled. A herbicide, maybe, but nothing fit. Then, that fall, he happened to visit the site on a day when a grounds crew was cutting trees. He saw the inner bark riddled with serpentine tunnels.

The extent of the damage struck him. “It seemed so aggressive.”

He would return to collect larvae-infested logs, breed out the bugs in a lab at MSU. By the end of May, he had green beetles that no one in Michigan could identify.

The entomologists got involved then, and the state and federal agencies. Teams of scientists made trips to the Detroit suburbs that June to inspect the dying trees. There was a growing sense of unease.

“As soon as we started looking under the bark of these trees, you knew something was going on,” said Deborah McCullough, an MSU entomologist. “Ash trees don’t have a native insect that feeds like that.”

Samples of the beetle went to experts in California and to Richard Westcott, an Oregon taxonomist who had worked with beetles for more than half a century. No match. More samples went out, to the Smithsonian Institution and the Natural History Museum in London, the two largest insect collections in the world. No match, again.

But there was still Eduard Jendek, an expert on Asian wood-boring beetles at the Institute of Zoology at the Slovak Academy of Sciences in Bratislava. They e-mailed pictures, then sent the small green bodies of the beetles across the Atlantic. On July 9, 2002, Jendek had the answer.

The next day Agrilus planipennis was found on the other side of the Detroit River in Windsor. Five days after that, the Michigan Department of Agriculture set up a five-county quarantine. What they didn’t know is that the emerald ash borer had already reached Cincinnati.

The species now known as the emerald ash borer became known to the Western world by way of a French priest and naturalist named Armand David, who made three trips through imperial China in the 1860s and ’70s.

David was the first European to lay eyes on the gerbil and the giant panda and dozens of other species. He sent four specimens of the creature he called the “yellow rat” from Mongolia to the Muséum d’Histoire Naturelle in Paris in 1866. The skins of the pandas came three years later.

He found the emerald ash borer in Beijing, according to a brief description of the beetle by the French entomologist Leon Fairmaire published in the Revue d’Entomologie in 1888.

That description, 67 words in Latin, the barest accounting of the borer’s physiology, was one of just a handful published in the west prior to the borer’s appearance in Michigan more than a century later.

Fairmaire assigned it to the genus Agrilus, a subset of jewel beetles and, with more than 3,000 species, the most populous genus of insects. He gave it the species name planipennis, a reference to its flat wings.

But it was a Czech entomologist named Jan Obenberger, publishing a separate description of the borer in 1930 and apparently unaware of Fairmaire’s account, who gave it the more prophetic name, evocative of trade routes between China and the West.

He called it Agrilus marcopoli.

“We knew nothing in terms of biology, except for a name we got from the Slovakian taxonomist,” said Houping Liu. “We didn’t know what kind of life cycle, what damage it can cause, even the host materials. We found them on ash, but we didn’t know if they were going to attack other tree species.”

Liu is a forest entomologist with the Pennsylvania Department of Conservation and Natural Resources. In 2002, he was a post-doctoral researcher at MSU but working with the U.S. Forest Service.

And it was in the campus offices of the Forest Service that the researchers had their first stroke of luck.

At the end of a 1998 trip to China to study the Asian longhorn beetle, a Chinese researcher had presented Robert Haack, an entomologist at the Forest Service, with a 1,000-page guide to Chinese forest pests written in Chinese. He couldn’t read it, but Liu could.

And, indeed, the book contained a description of the emerald ash borer, a page-and-a-half account of its life cycle and eating habits and the speed with which the larvae could kill a tree.

“It didn’t give us any of the real details,” Haack said, “because some of our Agrilus infest in the branches, some infest the major trunk, some are root feeders. And then we weren’t sure if there were any natural enemies.”

But it was something, one of just three published studies.

One of three because no one in China and other parts of its natural range cared much about the borer. They mostly didn’t have to. The Manchurian ash and Chinese ash and other Asian species have an evolutionary history with the insect. They produce compounds toxic to emerald ash borer larvae.

“If you go to China, the only trees that it’s going to attack, the only native ash trees, are trees that are really stressed,” McCullough said. “Dying. That level of stress.”

On a trip to China the following year, Liu and colleagues from China tracked down the researcher who had done the original article, hoping he had more to tell them about the borer, a habit, a weakness, an easy means of detection.

Chengming Yu was in his 80s by then. Liu never got to talk to him in person, but his Chinese colleagues did. Yu said he’d done his research back in the 1960s, after white ash trees were brought to China from the United States and all of them died from infestations.

But the older man had nothing more to say about emerald ash borer.

“If you know a little bit of history about China, there was a 10-year Cultural Revolution where all the intellectuals, the professors were sent to the countryside to do labor instead of doing research,” Liu said.

Yu had been among them. His research notes had been lost.

American chestnut trees once grew from southern Maine to the Florida panhandle and west as far as the Mississippi River. Their nuts supported sky-blackening flocks of passenger pigeons, broods of turkeys, raccoons and squirrels and deer and bears and humans, too. Their strong and rot-resistant wood became log cabins and split-rail fences, caskets and cradles.

In 1904, the chief forester for the New York Zoological Park found that chestnut trees on the zoo’s grounds had been attacked by an unusual fungus. That fungus would become known as chestnut blight. It probably arrived on imported Japanese chestnut trees. By 1950, it had killed virtually every mature American chestnut in the country.

In some areas of the Appalachian mountains, one tree out of every four had been a chestnut. The forests we have now are not the forests we had 200 or even 50 years ago.

“To somebody who doesn’t know anything about the woods, you go out and you see a lot of trees with leaves and it all looks great,” said Susan Freinkel. She is the author of American Chestnut: The Life, Death, and Rebirth of the Perfect Tree. “But if you know what ought to have been there, the kind of diversity that should have been there, then to you it looks like the wreck of an old cathedral.”

Some change is normal. Ecosystems rejigger their balance. Species lose ground to competitors, find new niches to exploit,

But as more container ships pass back and forth across the oceans, species are strewn and scattered at a faster rate, placed into environments where there are no predators to keep them in check, where their prey never evolved to resist them.

Take Dutch elm disease, the other famed killer of North American trees. It is a fungus carried by bark beetles. Elm species in Asia, where is probably originated, are reasonably resistant. European and American elms are not.

Dutch elm arrived on the East Coast of the United States in the 1930s. It has killed 100 million elms here since.

The first Europeans to lay eyes on elms in the New World had marveled at their grandeur, the architectural beauty of their limbs. They were part of the urban landscape from the early days of the republic, the dominant American street tree by the early 20th century.

And, when the elms began to die, cities replanted with maple and with ash.

Eradication

Before the emerald ash borer was found in the United States, there was the Asian longhorned beetle, an invasive killer of hardwoods found in New York and Chicago in the latter half of the 1990s.

Federal and state agencies pursued a strategy of eradication, chopping down infested trees by the thousands. When the fight against the emerald ash borer began, the methods used against the longhorned beetle seemed like an obvious template.

And, in retrospect, a bad one.

“We now know that Asian longhorned beetle and emerald ash borer are very, very different plant pests in terms of their biology and ecology,” said Paul Chaloux, national policy manager for the emerald ash borer program at the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, also known as APHIS.

Asian longhorned beetles are big, black and white and shiny. They chew dime-sized holes into the trees where they lay their eggs, a clear sign of their presence. They spread slowly, often re-infesting the same tree years in a row.

Emerald ash borer infestations typically aren’t visible until the trees are already half-dead. The borers are smaller. They lay their eggs covertly in cracks and crevasses in the bark of ash trees. Their larvae feed exclusively on the phloem, the part of a tree that carries nutrients from the leaves, killing their hosts with uncommon speed.

And they spread fast, unpredictably.

“There’s some portion—one percent, five percent, who knows—of these females that just take off and fly,” McCullough said. “They’ll fly by ash trees that look like they’re perfectly suitable and we don’t know why.”

Lab tests show they’re capable of flying as much as three miles in a day. Larvae carried along in firewood can go much farther, which is probably how the emerald ash borer reached Boulder, Colo., where it was discovered last fall, hundreds of miles from any previously discovered infestation.

“With a number of the pests that our agency has historically dealt with, it’s relatively difficult for the average person to move the pest,” Chaloux said. “The average person very rarely handles whole wheat grain, so a pest of wheat is not something that the average person is likely to move around.”

“The average citizen certainly can and, we have evidence, certainly has brought the EAB to new locations,” he said.

The five-county quarantine established in 2002, restricting the movement of ash nursery stock and logs and any sort of firewood, quickly expanded to six counties and then 13 and then 20, growing as the true extent of the infestation became clear. It hasn’t stopped expanding.

In 2004, Canada cut more than 60,000 ash trees between Lake Erie and Lake St. Clair to create a six-mile-wide barrier they hoped the borer couldn’t cross. The next year, satellite populations were found on the other side. Plans for a similar ash-free zone in Michigan were never realized, largely because of difficulties in delineating just where the infestation stopped.

None of the 12 specialists interviewed for a 2006 report on from the General Accounting Office believed eradicating the borer was still possible.

“It became very evident that the tree removal campaign was certainly not going to be effective,” Chaloux said.

USDA program managers also told the GAO that they were concerned about cuts in funding for the emerald ash borer program. Without the resources to pursue the beetle aggressively, they said, it was likely to spread farther and cost more in long run.

White ash has been the preferred wood for baseball bats for more than a century. Maple bats surged in popularity after Barry Bonds used one to hit 73 home runs for the San Francisco Giants in 2001, but roughly half of the players in the majors still use ash.

The emerald ash borer hasn’t changed that. Not yet.

Louisville Slugger uses white ash harvested from northern Pennsylvania and New York. The ash borer arrived in western Pennsylvania in 2007.

“This spring, it was discovered within about 50 miles of where we harvest our timber,” said Rick Redman, a spokesman for the company.

White ash is valued for its strength and flexibility. It doesn’t shatter the way maple does. But the company has been exploring other types of wood: several species of birch and beech, as well.

The popularity of maple has been “a bit of a blessing,” Redman said. “If ash wood were to go away, at least there’s the maple option.”

A visual bug

Few people understand the borer’s ability to confound those who would track its spread better than Therese Poland.

She’s an entomologist with the U.S. Forest Service in East Lansing and the owner of what is probably the world’s only anatomically correct, hand-knitted emerald ash borer, a gift from an assistant. Almost immediately after the borer was discovered, she began putting ash leaves and the beetles themselves into ethanol, making extracts, analyzing them with gas chromatography and mass spectrometry, hooking the borers into electro-antennal detectors to see which compounds they respond to.

The hope was to find something that could lure the beetles from a distance, bring them into traps, allow researchers to track small infestations as well as devastating ones.

Alas, the emerald ash borer is a visual bug. If humans had eyes of the same proportion to our bodies, they’d be the size of grapefruit. It has certain preferred colors, as reflected in the Barney-the-Dinosaur-purple now used for emerald ash borer traps, and it likes the silhouettes of trees, but visual cues don’t exert a long-distance pull.

There are compounds that attract it, Poland said. There is a green leaf volatile called cis-3 hexenol and a number of sesquiterpenes from ash bark that, as luck would have it, are pretty well mimicked by commercially available manuka oil. Canadian researchers are working on what might be a short-range pheromone.

“We have traps now that are better than nothing,” Poland said, “but they’re not super sensitive at detecting low infestations. It’s very hard to find it early. Usually, by the time we find it, it’s been there for a few years.”

The Congressional Research Service pegs the cost of the estimated 50,000 non-native species in the U.S. at $129 billion each year. That’s everything from dense stands of leafy spurge supplanting grasses on grazing lands in the west to quagga mussels clogging the water intakes of nuclear power plants on the Great Lakes to the cumulative effect of six million feral swine foraging on crops.

The federal government spent $2.2 billion in 2012 to combat invasive species and to prevent new entries. The USDA spent $26.8 million that year to fight the emerald ash borer. In 2013, it spent just $10.7 million.

The emerald ash borer probably costs at least $1 billion each year in the U.S. That figure comes from studies by the U.S. Forest Service, and it only takes into account the removal, treatment and replacement of trees in urban areas. Another estimate, from a team of U.S. and Canadian researchers, placed annual damages at $1.6 billion including the loss of residential property values and timber.

The timing of the invasion exacerbated that burden. By the time the borer was discovered, Michigan was already entering a single-state recession. Cities and property owners were stuck paying for the removal of dead trees and planting new ones if they could afford it.

The emerald ash borer was found in Ingham County in 2003 in nursery trees planted at Meridian Mall and elsewhere. In Lansing, it was 2006 before the ash tree started dying in large numbers. The city removed approximately 6,500 ash trees at a rough cost of $800 each, said Paul Dykema, assistant superintendent of operations and maintenance, though he cautioned that no one had calculated the city’s total cost.

“It’s taken them out of the landscape entirely,” Dykema said.

The champion

The green ash tree that hangs over the intersection of Topash Street and Townhall Road north of Dowagiac has a trunk that measures 22 feet around and a lifespan that can be measured in centuries.

At one time, it was the largest green ash in the country: 95 feet tall with a spread to match, “but that’s all disappearing,” said Tim Watson, who has owned the property where the tree stands since 1985.

David Milarch came, the Copemish nurseryman who has spent two decades cloning the country’s oldest and largest trees and replanting them. He has planted clones from the green ash on the grounds of the U.S. Capitol and the Pentagon and the National Museum of Forest Service History in Missoula, Mont. and other places, too.

It was nice, Watson said, “just knowing that it was a champion tree.”

The emerald ash borer arrived in Cass County in 2007. Watson said he heard about the bug, but “never knew anything about it.” He doesn’t know if it reached the champion ash. What he knows is that the crown of the tree is half bare, that branches are falling off during wind storms.

“When we moved here, it was in full bloom every year,” he said, “but it’s just slowly, slowly been dying off.”

The emerald ash borer costs the city of Milwaukee is $980,000 a year, but ash trees are still very much part of the city’s streetscape. The money pays for insecticide treatments, 14,000 ash trees each year.

Milwaukee took an uncommonly deliberate approach to the invader. It assessed its urban canopy in 2008, found that ash trees made up nearly a fifth of it and started a conversation about what it would really mean to lose them.

“We knew we’d have other ancillary impacts,” said city forestry services manager David Sivyer.

Trees intercept rainfall and so blunt the impact of heavy storms on city drainage systems. Their shade keeps temperatures lower in summer, reducing the energy used for air conditioning. Many species intercept and sequester airborne pollutants. And then there’s the cost of replacing, not just trees, but trees that have survived long enough and grown large enough to provide those benefits in a meaningful sense.

“It turns out that our trees are providing some $15 million annually in storm water benefits and almost $4 million annually in other benefits: air quality, energy reduction and carbon sequestration,” Sivyer said.

Which wouldn’t have mattered even a year prior. But, in 2008, a Massachusetts company called Arborjet released TREE-äge®, the first insecticide that really worked on the emerald ash borer. McCullough at MSU did the testing. It killed more than 99 percent of emerald ash borer larvae in treated trees and 100 percent of the adult beetles that nibbled on their leaves. A silver bullet with limitations, among them the fact that it had to be injected directly into each tree.

That required knowing the location of every ash tree in a 97-square-mile city, which Milwaukee got by paying for hyperspectral imaging of the urban canopy. Where the human eye sees three bands in the visible light spectrum, hyperspectral cameras can see hundreds. Used properly, the data in the images can be used to make all sorts of fine distinctions, between tree species for example, based on the unique way that they reflect light. Milwaukee checked for false positives with a small army of interns.

The emerald ash borer was found in Milwaukee in 2012, an infestation on private property that had begun at least four years prior. The ash trees lining the adjacent street were healthy. They still are.

“This tree has begun to form scar tissue.” Leah Bauer had her hand on the trunk of a thin ash tree in Central Park in Okemos, just north of Meridian Mall.

“If I were to cut into here, we would have live phloem, right here and over here,” she said, “which is why this branch is alive.”

There are ash trees growing in the forest here, stump sprouts, saplings that lingered in the forest understory until a gap in the canopy gave them light and room to grow, survivors. Bauer, a U.S. Forest Service entomologist, is keenly interested in their success because she is keenly interested in whether the wasps are doing what they’re meant to.

From the start, the federal government’s efforts to combat the emerald ash borer included a trickle of money for what’s known as bio-control. It has since become the focus.

The emerald ash borer has few natural enemies in North America—woodpeckers are an exception—and so in 2003 researchers from the Forest Service and APHIS and colleagues from China began searching in the borer’s native range for parasites. They brought back three species of tiny stingless wasps.

Oobius agrili—Bauer calls it “oobs”— is the size of a poppy seed and lays its eggs inside borer eggs. The slightly larger Tetrastichus planipennisi, or “tets,” lays eggs inside borer larvae. The hatching larvae of Spathius agrili feed and develop on ash borer larvae.

Researchers first had to determine that the wasps wouldn’t wreak havoc on North American ecosystems. In 2007, they began releasing small numbers of them at test sites in mid-Michigan. A breeding facility opened in 2009 in a nondescript building just off of Grand River Road in Brighton with cold storage rooms in the basement that are filled with emerald ash borer–infested logs.

The borers are bred out in cardboard drums. The wasps are bred on borer eggs and larvae and then shipped to 17 states for release. The EAB Biological Control Production Facility produced more than 200,000 wasps in 2012, more than 550,000 in 2013. It’s on track for 735,000 this year, said team leader Scott Whitehead, more of the Tetrastichus planipennisi than the others.

“Those are the ones, you can get 150 wasps out of a single exposure,” he said. “There’s more bang for the buck.”

It’s Bauer’s job to determine how the wasps establish themselves in the wild, what impact they have on emerald ash borer populations and how that matters for ash trees. She has been been observing populations at six sites in Ingham, Clinton, Shiawassee, Saginaw and Gratiot counties.

At one and only one site, the ash trees are growing bigger, she said. She needs more data. It’s not the sort of study that happens quickly. The life cycle of a tree is long.

According to a story told by Anishinabe people in Michigan and elsewhere, the first black ash tree grew from the cremated body of a man named Black Elk.

Nearing the end of his life, the story goes, Black Elk asked the creator for a way to help his people. He was given a vision. His people were to watch over the tree that would sprout from his buried ashes, to hold it sacred. He saw how it could be cut down, how to separate the growth rings from one another, how to fashion the wood into baskets.

“The black ash tree has been used by our people for centuries and centuries,” said Kelly Church. “It’s a tree that is very flexible, so when you pound the growth rings apart, you can bend it, twist it, you can steam it. We make cradle boards from it, snowshoes, baskets.”

Church is a basket maker from a family of basket makers, part of the Grand Traverse Band of Ottawa and Chippewa Indians. Her house outside of Hopkins has largely been given over to studio space for her elaborate, often colorful, creations.

But the trees that that supply her working materials are dying. Different species of ash have different levels of susceptibility to the emerald ash borer. Blue ash, named for the blue dye that can be extracted from its inner bark, is relatively resistant, white ash a little less so. Green and black ash are the most vulnerable.

“The black ash trees dying is like losing a part of our culture,” Church said. “It’s going to be devastating, for the future generations especially.”

For other tribes, too. In the creation myth of the Wabanaki tribes in New England, for instance—the Penobscot, Passamaquoddy, Maliseet and Micmac—the black ash is the source of humankind. Glooscap, who came into their lands “first of all,” shot arrows into black ash trees. Humans came out from under the bark.

Insecticides won’t help save trees for the basket makers. It wouldn’t be safe. They use their hands in the manufacturing process, their mouths, too. Since the threat of the borer became clear, there have been conferences and seed collection programs, efforts to document the basket-making process and to teach the young who might be alive to see the black ash restored.

It’s not as if another tree would work, Church said. Traditions don’t swap out so simply.

“It’s kind of like saying, ‘We lost our language. Let’s just make up another one.'”

Even in the southeast corner of Michigan, where more than 99 percent of the mature ash trees have died, a few survive, a few tenths of a percent of a population that numbered in the millions. Dan Herms and his colleagues are trying to figure out why.

“The big question is, ‘Are those ash trees actually resistant or are they just lucky?'” said Herms, an entomologist at The Ohio State University, “because, if you look at the rate at which trees die, it’s a bell curve. By definition, there’s going to be a few remaining trees out on the tail of the bell curve, even if it’s just natural luck.”

Lingering ash. That’s what they call the survivors. Herms and his colleagues have collected their buds, planted clones to be exposed to the emerald ash borer. They don’t know yet if the native resistance is real, but it would be “the ideal situation,” Herms said.

It’s not the only solution. It should also be possible to cross North American ash with the resistant trees from China, to produce trees that are nearly identical to the American species genetically but also able to protect themselves from the borer.

The goal, Herms said “is to essentially do what natural selection has done over evolutionary time,” only to do it far more quickly.

Identifying the genes that make Chinese trees resistant to the bug is “just a matter of time and perseverance,” Herms said.

He’s hopeful on that front.

The deaths of 100 million trees have consequences.

There are, for instance, at least 260 species of insects that use ash trees as a host, at least 44 that do so exclusively. Gaps that have opened up in the forest canopy are allowing invasive plants to thrive on the forest floor, buckthorn and honeysuckle and multi-floral rose. In rivers and swamps where the ash have died, the water chemistry and temperature and flow are changing

And the emerald ash borer will kill more trees. Scientists have found many ways to slow it down, but no way to stop it on a large scale.

“I guess I expect that it will eventually spread from coast to coast,” McCullough said.

The hope is to buy time, to find new tools, to keep the ash trees alive long enough to save them.

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