Each year more and more American elm trees, which once lined hundreds of town squares, fall victim to Dutch elm disease. Last year the apparently incurable blight destroyed at least half a million trees in the U.S. This summer the pestilence may be worse; it has spread from the East through the South and Midwest and is now attacking trees as far west as Denver.
After every other remedy failed (including such folksy "cures" as injecting trees with turpentine or whacking galvanized nails into their trunks), scientists believe they have found a way to stop the fungus that causes the disease and...