Shadowed Elm

Fighting for a favorite tree

Graceful and majestic, their delicate, almond-shaped leaves framed against summer skies, elms once grew thickly in the forests of the eastern U.S. and served as shade trees along thousands of Main Streets. Then, in the early 1930s, disaster struck. A load of elm logs arrived from Europe infested with a parasitic fungus. First identified in 1919 by Dutch plant pathologists, the fungus, Ceratocystis ulmi, invades the elm's vascular system, clogging it and causing death. Beginning in the Cleveland and New York City areas, then in scores of other communities across the nation, American elms died by the thousands from the fungal infection: Dutch elm disease.

Even now, more than 60 years after its discovery, the blight annually kills 400,000 trees in the U.S. Cutting and removal--the only sure way of stopping the spread of the fungus, which is borne chiefly by bark beetles from tree to tree--costs $100 million a year, to say nothing of the aesthetic price. In many Northern cities, once shaded thoroughfares are treeless and barren. In Milwaukee, where more than 100,000 elms flourished in 1956, barely one-fifth still stand. In Champaign-Urbana, Ill., there were 14,000 elms at the end of World War II. Now there are only 220. A celebrated loss occurred a year and a half ago, when one of the most venerable elms on the White House lawn, a 105-ft. giant planted in the days of Rutherford B. Hayes, had to be felled and carted off.

With generous government and private funding, botanists, arborists and plant pathologists have been trying to stem the epidemic, but with only limited success. They have developed effective fungicides, for example, but when these chemicals are injected into the trees, they do not penetrate all the infected parts. Other strategies under test include trimming or fumigating the roots between diseased and nondiseased trees, which can provide another pathway for the infection.

At the University of Wisconsin in Madison, scientists have resorted to cloning, hybridization and other techniques to develop many kinds of disease-resistant elm. But none look like Ulmus americana, and all proved unpopular. Says Plant Pathologist Eugene Smalley: "The resistance thing is the easy part. Getting a tree that nurseries will use, that's tough." Smalley's best hope: a rare hybrid called the Sapporo Autumn Gold elm, a cross of Japanese and Siberian elms. It resists the disease and, at least in its youth, resembles the American elm.

The latest tactic against the fungus pits bug against bug. Plant Pathologist Gary Strobel at Montana State University has been injecting pseudomonad bacteria into infected trees: the microbes multiply and attack the fungus. Strobel's program is still in the experimental stage, but there have been some modestly promising results. In Sioux Falls, S. Dak., for instance, injections were given to 20 badly diseased trees; seven were saved.

For now, the best preventive medicine, other than prompt removal of infected trees, is constant vigilance, spraying and pruning. New York City has 33,000 American elms, one of the largest municipal collections in the East. Fewer than 1% died last year, largely because the elms are doused each spring with a chemical that discourages beetles from nesting, and park rangers and volunteers conduct "elm watches" to spot the disease (early signs: wilting, curling and yellowing leaves; thinning of the tree's crown; brown streaks under the bark). An aroused citizenry helps keep the pressure on city hall; last month elm lovers in the Big Apple staged a protest saying not enough was being done to save the trees.

In planning Disneyland, which opened in 1955, Walt Disney solved the problem in a novel way. He lined his idealized Main Street, U.S.A., through which all visitors must pass before getting to Tomorrowland or Frontierland, with Chinese elms. They are not quite look-alikes of their American cousins, but do grow in balmy Southern California. More important, they resist Dutch elm disease. qed

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