For horror movie aficionados the scariest thing about Elm Street is Freddy Krueger. But an arborist is more likely to lose sleep worrying about an encounter with the dreaded elm bark beetle. Although this beetle is just one-eighth of an inch long and lacks Krueger's sense of showmanship, the Dutch elm disease (DED) fungus it transmits is just as deadly as one of Freddy's trademark slashes. So while Freddy vs. Jason is playing on the Big Screen, an even more intriguing showdown is taking place in the real world, with Elm Watch—a Massachusetts-based non-profit that encourages the protection of elm trees—facing off against the elm bark beetle, ensuring that its potential victims will not be cut down without a fight. It might be a losing battle, but with Elm Watch on the lookout, American elms just might have a chance to live another day.
From the 1800s until the middle of the 20th century the American Elm (Ulmus americana) was the predominant shade tree in towns and cities throughout the northeastern United States. Majestic and aesthetically pleasing, its stress-resistant constitution allowed it to withstand the diverse environmental stresses associated with city conditions. In fact, the American elm might have retained its most-favored status in perpetuity if it weren't for the fungus (Ophiostoma novo-ulmi) that causes DED (itself a misnomer, since it's native to Asia but was first identified by a Dutch biologist). In the early 1930s, elm veneer logs infected with the fungus were imported from France to the U.S., then shipped overland to furniture manufacturers in Ohio. “You want to talk about bioterrorism? That was it,” says Tom Zetterstrom, founder and spokesman for Elm Watch. “It was the train of death, right into the heartland of America.”
Within a few years the elm bark beetle was transmitting the fungus throughout the natural range of the American elm—from Canada to Florida and across most of the United States—and trees began dying by the millions. The fungus is transferred when a beetle feeds on an infected elm, picks up microscopic spores on its body, flies to the next tree and feeds again. The beetle does no direct damage, but the newly deposited spores establish themselves and the following summer visible symptoms become evident. “You'll see a little bit of yellow in June, July and August when the tree should be green,” says Zetterstrom. “Then the leaves start to curl and shrivel and turn brown as the fungus clogs the vascular system.”
Once an elm is contaminated its chances for survival are slim, even if, as recommended, fungicide is administered and the infected limbs are amputated eight to ten feet below the infected portions. “Early detection is critical,” maintains Zetterstrom. “If you have only five percent exposure and you do the proper surgical procedure of cutting that out and treating the tree, the chances are maybe two-thirds you can save it. But if you have ten percent exposure it drops down to 17 percent and if it's more than that you're down to three percent.”
Rapid response is even more imperative when other elms are standing nearby. “If the trees are growing in a row and left untreated the fungus progresses down the branches, through the main stem and into the root system,” begins Zetterstrom. Because the roots of nearby trees fuse underground the fungus can be sucked up from one tree into the bottom of its neighbor. “That tree dies very quickly because it's hit right at the base. Interrupting and breaking that junction can be an important treatment scenario,” says Zetterstrom, before noting that the alleys of elms that were once found lining American streets are almost unheard of today.
The Roots of Elm Watch
Growing up in New England in the 1950s and ’60s, Zetterstrom was exposed to the plight of elms at an early age. His father, a tree surgeon, spent a considerable amount of his time cutting down diseased elms. “When I was a little kid, my dad would be removing trees that required a five-foot, two-man chainsaw to cut through,” he remembers. In high school he began working side-by-side with his father, cutting down trees and spraying pesticides. In those days combating DED meant spraying elms with the pesticide DDT (dichlorodiphenyltrichloroethane), hardly a targeted strategy. “It killed the elm bark beetles plus almost everything else it came into contact with,” notes Zetterstrom.
After finishing college in 1970, Zetterstrom left the tree business and went on to teach photography. But over the years he noticed that roadside elms throughout northwest Connecticut and western Massachusetts were continuing to die off, and nobody seemed to be doing anything about it. “I [was thinking], ‘Hey guys, why don't you get that diseased elm out of here quickly, so you don't have two or three to remove?’” says Zetterstrom. Finally, he decided to take action, and began by protecting a single tree—a particularly magnificent specimen in Egremont, Massachusetts, that is thriving today as a result of his efforts. Still, Zetterstrom wishes he had started Elm Watch a long time ago, as many more magnificent elms might have been saved. “I should have been smart enough to think of this 20 years before I did. I didn't act decisively to interrupt the transmission cycle of the disease,” he says.
Ironically, preserving the remaining elms requires Elm Watch to take a seemingly cold and calculated approach. The most cost-effective method of control is called sanitation—simply getting rid of the source of the contamination. You can think of the procedure in terms of a horror film, as the tools employed by a tree surgeon and movie serial killer—an ax or chainsaw, and an incinerator or wood chipper—are often one and the same. Sanitation involves killing off the offending individual (the diseased elm) and then properly disposing of the body (the trunk and branches) by burning or shredding, so it won't be a nuisance or come back to haunt you (infect other elms).
However, getting community government and ordinary citizens to accept tree removal isn't as simple as it might seem. Just like horror movie victims are often caught unaware by an impending threat, most people aren't conscious of the danger posed by diseased trees. And just like law enforcement never seems to be around when a movie killer is on the prowl, most tree wardens are ill equipped or simply too busy to deal with issues related to illness. “Tree wardens have other things on their minds—primarily asphalt, plowing and mowing lawns. They're not hip to tree care,” says Zetterstrom. In that respect, both Massachusetts and Connecticut are ahead of the game, as Elm Watch has a relationship with MassHighway [the Massachusetts Highway Department] and the Connecticut Department of Transportation whereby Zetterstrom can request removal of infected elms.
Yet, even when public officials are onboard, all it takes is one uninformed individual to delay or block the process. “When MassHighway came to take one down in Sheffield a woman got out in front of the tree and wouldn't let them take it down,” reports Zetterstrom. The woman's complaint was that the tree wasn't completely dead—it was still three-quarters green. Nevertheless, the sick individual was a danger to every other elm in the area. “Procrastinating and being too emotional is not in the interest of elm management,” he advises.
Drugs Not Hugs?
The other primary method of combating DED is both proactive and highly targeted—macro-injection of healthy elms with a fungicide called Arbotect (thiabenzadole). The hour-long procedure is performed by a professional arborist, and involves drawing back the soil around the base of the tree and injecting a diluted mixture of the fungicide into the root flare. Then nature takes over and the tree naturally sucks the moisture up throughout its system. “The idea is to get it [the fungicide] out there to the outer periphery of the branch tips where the fungus is deposited [by the beetle],” says Zetterstrom. While Arbotect drastically reduces the chance of a DED infection, the procedure—$500 for a tree three feet in diameter—must be repeated every three years and cannot save an already-contaminated specimen.
To encourage individuals to contribute to the cause, Elm Watch started the Adopt-An-Elm initiative, whereby donors can sponsor the treatment of one or more trees. To date, Elm Watch has protected 118 elms, although Zetterstrom acknowledges that protecting elms one-at-a-time is a decidedly labor-intensive process. As a result, Elm Watch is now working to persuade towns and cities to include elm protection in their annual budgets—ensuring that the trees will receive their injections without interruption.
Survival of the Fittest
Of course, Elm Watch isn't the only group looking out for the future of elm tress. For the past 20 years, the Floral and Nursery Plants Research Unit of the U.S. National Arboretum has been testing American elm cultivars to determine the most disease-tolerant varieties. According to Zetterstrom, “they grow the trees up to a reasonable size and then methodically inject them with a solution of the fungus.” It's the equivalent of deliberately injecting the HIV virus into a human being. But by testing more than 50,000 seedlings the researchers have identified two particularly disease-tolerant selections—Valley Forge and Princeton—both of which are likely to play a leading role in the restoration of elm populations.
Meanwhile, building on the work of the National Arboretum, Elm Watch is beginning to pursue what Zetterstrom refers to as community forestry. The organization plants young disease-tolerant elms in the hope they will one day grow to complement the architecture of towns across New England, just as they did in past centuries. “These elms are not placed willy-nilly. They are placed precisely where they should be—with an understanding of how they are going to relate to architecture, the motorists' experience, safety, and the condition of the soil,” he emphasizes.
He also notes that restoration is a daunting task these days, largely because you can't just plant a tree wherever you want anymore. “Now you've got to pick out the site, get everybody's permission, contact ‘Call Before You Dig,’ get a backhoe, dig the hole, enhance the soil—we have a whole checklist for elm restoration procedure,” he continues. But despite all the trials Zetterstrom finds the process rewarding: “I am taking great pleasure in the vision that these plantings involve. When I drive down the road I am now imagining these trees full blown.”
Nightmare on Oak Street? Ash Street? Maple Street?
While Zetterstrom is relatively optimistic about the prognosis for elms he is less sure about the outlook for trees in general. “The great loss that preceded DED was the American chestnut blight [in the first 40 years of the 20th century, 3.5 billion trees died], which wiped out an equally beloved and very, very significant forest tree,” he reminds. But these days there's plenty of new diseases and pests to worry about—California's Sudden Oak Death syndrome and the emerald ash borer that is killing trees in Michigan—to name a few.
He's also concerned about globalization and the ramifications of intercontinental trade, which inevitably introduces contaminants that were once geographically confined, to new, far-flung places. In August of 1996, a shipment of goods imported from China to New York delivered an unwelcome visitor—the Asian longhorned beetle. Since then, untold millions have since been spent trying to locate, contain and eradicate these beetles, which threaten the maple population, the American elm and a variety of other trees. “It's an alarming situation and I'm not an alarmist,” asserts Zetterstrom. “These invasives take off because there's no natural check on them.”
Not surprisingly, Zetterstrom advises individuals to resist becoming overwhelmed by macro-level issues. Aside from contributing to the Adopt-An-Elm initiative Zetterstrom encourages would-be activists to start a local tree committee and push for their town or city to hire a qualified tree warden—“someone who is not just dealing with hazard trees and branches that killed someone”—as he puts it. Alternatively, individuals can educate themselves about the disease-tolerant varieties that are now commercially available and plant an elm or two themselves.
However, Zetterstrom urges communities to heed the lessons of the past century. “The elm is still an extraordinary tree. That's why they were over planted, and every Elm Street had nothing but elms,” he begins. “But it's biologically unstable when you invest everything in one stock. We're trying to encourage diversity—the ideal mix is not more than ten percent of one species in a healthy community forest environment.”
The Real Slim Shady
At the same time, it's possible to look back at history to see how elms were once an integral part of landscapes and streetscapes—and to understand how we might learn to appreciate them again in the future. A recent book entitled “The Republic of Shade: New England and the American Elm,” by Thomas J. Campanella, examines Native American relationships with the land and relates how, over time, New Englander's discovered the value of elm trees.
According to Zetterstrom, consciousness raising is a big part of his responsibility, and he considers it a big plus when Elm Watch can plant a young elm where a historically significant elm once stood. “What we're planting may look like a stick with some leaves on it, but you have to understand it's potential,” he says, pulling out a picture from days gone by to demonstrate his point. "Look at how incredible this town once looked. At one time it was just chillingly beautiful.”
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