ORIGINALLY PUBLISHED IN
USA Today
Arlington; November 6, 1997
The Great Elm Returns
DENNIS CAUCHON
New tree survives Dutch elm disease
The beloved American elm once arched over the streets of this nation, forming long, shady cathedrals of nature that defined the look of this country's for two centuries.
The United States has never looked the same, never looked as good, since a tiny beetle landed in Cleveland in 1930 on a log aboard a ship from England. the European elm bark beetle brought Dutch elm disease, a fungus that has killed hundreds of millions of elm trees -- as many as 95‰ of American elms -- in the greatest ecological accident to strike North America.
Now, in the most important development ever in the fight against Dutch elm disease, the U.S. National Arboretum has developed an American elm tree that possesses an extraordinary genetic ability to withstand the fungus. When injected with massive amounts of the most deadly strains of the disease, this remarkable American elm wilts only slightly and then recovers to full health.
The tree, named the Valley Forge elm, culminates 60 years of government research, involving three generations of scientists and tests on 60,000 elm trees. The Valley Forge elm has been shipped to 17 wholesale nurseries and will be available to the public in the year 2000. It will be the first American elm to be widely planted in 50 years.
These trees may restore the American elm to its historical position as the nation's pre-eminent tree. "In 2010, the elm tree will once again be the most popular tree in the country," predicts T. Davis Sydnor, professor of urban forestry at Ohio State University. "I don't think it can be stopped because, other than a soft spot for Dutch elm disease, it is the perfect city tree."
The American elm is known for its craggy bark and stately beauty, a Y-shaped form that grows 60- to 100-feet high. But the tree's greatness also springs from its unique ability to survive city life. Better than any other trees, the American elm withstands smog, drought, floods, heat, cold, poor soil, vandalism, lawn mowers and de-icing salts.
As testimony to its versatility, the American Elm grows naturally in North Dakota riverbeds, Louisiana swamps and Maine's thick woods. Yet the tree is equally well-adapted for life as a landscape tree in Manhattan or a Kansas City suburb.
American colonists planted elm trees near their homes in the 1600s. George Washington took control of the Continental Army in 1775 under an American elm in Cambridge, Mass. Pioneers brought the tree west in covered wagons as early as 1835. Elms dominated nearly every city and college campus by 1930. What the maple tree is to Canada, the American elm is to the United States -- part of the national experience.
The original log infected with Dutch elm disease was put on a train in Cleveland and shipped to a Cincinnati furniture factory. Soon, elms along the railroad tracks began dying. Tree experts knew immediately that disaster had arrived. Dutch elm disease, named after the Dutch researchers who isolated the fungus, had already killed millions of European elms.
The long war to save the elm
For a half-century, the United States waged a costly war against Dutch elm disease, involving hundreds of researchers, most major chemical companies and city foresters across the country. The fungus won.
"The war against Dutch elm disease turned out to be like the war against cancer: far more difficult and complex than we realized in our youthful optimism," says Gene Smalley, 71, a leading elm researcher at the University of Wisconsin.
The fight seemingly lost, Dutch elm disease research has dwindled to almost nothing today, just a handful of middle-aged researchers who wouldn't give up.
One of the stragglers is Denny Townsend, a mild-mannered tree geneticist at the National Arboretum's research farm in Glenn Dale, Md. He drives a 1985 Oldsmobile Delta 88 with 107,000 miles on it; it replaced a Chevy Caprice with 199,000 miles. Tree people don't like change. "We're patient sorts," he says.
Townsend, 55, discovered the Valley Forge elm through an unusual combination of rigorous science and pure luck.
The seed that became the Valley Forge elm was one of thousands of elm seeds collected by researchers around 1960. It isn't known what tree the seed came from or whether the tree still lives.
Townsend estimates that only 1 in every 100,000 American elm trees possesses any anti-Dutch elm disease qualities. He has spent his career looking for that longshot.
Townsend concentrates on elm trees that have survived outbreaks of Dutch elm disease. These survivors are often the only trees left standing in forests or parks where hundreds of elms once grew. It was hoped that these survivors possessed some special genetic quality that made them immune or at least tolerant of the disease.
But hundreds of survivors turned out to have no special resistance."It turned out most of the trees were just lucky," Townsend says.
In 1988, Townsend decided to run one more series of tests. He choose ten different types of American elms and grew 28 trees of each variety, using seeds researchers had collected over many years. In 1992, when the trees were 6- to 13-feet tall, Townsend injected each tree with one million spores of the most aggressive strains of Dutch elm disease, a far more lethal dose than the 10 to 100 spores that trees get in nature.
A year later, Townsend had a large patch of dying trees.
But one type of tree behaved differently. It barely wilted. Even more amazing, a year later, it was healthier than before. Two years later, it had no trace of the Dutch elm disease.
Townsend had done arboriculture's equivalent of striking gold. He'd found a classic American elm that, for reasons unknown, survives the most vicious cases of Dutch elm disease.
Townsend renamed American Elm No. 3 as the Valley Forge elm, in honor of George Washington's troops who overcame almost insurmountable odds to survive the winter of 1777-78 at Valley Forge, Pa. Townsend shares credit for discovering the Valley Forge elm with his retired colleague, plant pathologist Larry Schreiber, and technician Warren Masters.
Valley Forge elm lives to see another day
Recently, Townsend drove his Oldsmobile down a dirt road to visit his Valley Forge elms at the National Arboretum's research farm. The Valley Forge elms have grown from 11 feet tall when injected with Dutch elm disease in 1992 to 19 feet tall. "It's a very good sign that five years later the trees have come back with no symptoms on new growth," he says.
"This is very important and very well done research," says Richard Campana, 79, professor emeritus at the University of Maine and a Dutch elm disease expert. "While nothing is certain, these new elms seem to be a real breakthrough." Still, Townsend, who has graduate degrees from Yale and Michigan State, advises caution: "I hope people don't go out and start planting the whole town with Valley Forges. They'd open themselves up to disaster. Diversity is the key."
Tree experts now say that no single species -- such as pin oak, Norway maple or American elm -- should account for more than 10% of a city's trees. Planting too many trees with similar genes leaves a city vulnerable to one disease. Cities should limit elm-lined streets to two or three blocks in a row.
To encourage diversity, the National Arboretum released another elm tree along with the Valley Forge: the New Harmony elm. It showed about one-fifth the disease tolerance of Valley Forge, when measured by the percentage of dead branches. It will be available in 2000, too.
Another tree, the Princeton elm, also showed disease tolerance similar to the New Harmony elm. Princeton Nurseries of Allentown, N.J., had stopped selling the tree in 1935 because of Dutch elm disease. Recently, though, Princeton Nurseries began selling a few hundred a year to retail nurseries.
Although not as tough as the Valley Forge elm, the New Harmony and Princeton elms have good survival chances because nature's test is less demanding than Townsend's scientific one.
The disease-tolerant elms may make it possible to crack the genetic code of Dutch elm disease, knowledge that would allow the creation of many varieties of disease-tolerant elms.
"The only thing we know for sure is that all the old theories were wrong," says Joseph Kamalay, 47, a molecular biologist at the U.S. Forest Service. "I'm optimistic that the Valley Forge and New Harmony have something important to tell us about how to save the American elm."
In a government lab in Ohio, Kamalay and biochemist Steve Eshita are examining how the Valley Forge and New Harmony elms fight Dutch elm disease. Promising new evidence indicates at least two defense mechanisms are at work:
The trees stop the Dutch elm disease fungus from germinating, the first of many stages in its complicated life cycle.
The cells of disease-tolerant trees go dormant after a Dutch elm disease attack but then snap out of it. The cells of doomed elms remain forever dormant.
Townsend is preparing for what will probably be the final Dutch elm disease experiment of his career. He has mated the Valley Forge elm with five other American elms in hopes of creating an even tougher American elm.
In soybean or tomato research, several generations are bred every year to speed genetic selection. But each tree experiment takes seven to 10 years. No growth hormones, fertilizers, insecticides or fungicides are used.
"It's like breeding race horses -- only slower," Townsend says. "Breeding and selection is the way to go. It just requires patience.
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See also:
Elm has Deep Roots in Nation's LandscapeAllan McCollum / PARABLES