The stately U.S. elm, which inspires the weekend artist and dandles the infant oriole, is in worse danger than ever. Last week, the U.S. Department of Agriculture warned that the Dutch elm disease, a familiar menace in the Northeast, had spread during the war into new territory: Delaware, Kentucky, Vermont, Virginia. Sweeping out of the Middle West was an even more deadly disease, phloem necrosis, which kills thousands of elms every year.
No one knows how phloem necrosis spreads. Dutch elm disease is better understood; it is a fungus carried from elm to elm by small bark beetles. They slip through the...