Doomed Elms

The National Shade Tree Conference is an annual gathering of men who raise and sell trees for landscape decoration, other men who study trees for pure science, still others who are professionally interested in national reforestation. Last week about 200 such men met at the New York Botanical Garden for their ninth conference. The tree which most occupied their dendrological talk was the stately American elm, which a blight has begun to attack. Unforgotten is the disease which wiped out practically every U. S. chestnut tree. Plant pathologists have found that elms are now being killed by a fungus, Graphium ulmi. The blight reached the U. S. in 1930 in some Carpathian elm logs shipped from Le Havre. It accompanies the beetle Scolytus multistriatus. This is a small, short-beaked beetle which nips the tender elm bark and shoots near the buds. Graphium ulmi enters the wounds. First external sign of the disease is the wilting and yellowing of leaves. Internally twigs become streaked with brown. The elm is doomed and must be drastically pruned or felled. All cuttings must be burned to prevent further spread of Graphium ulmi. The Ohio Agricultural Experiment Station at Wooster, Ohio, whose John Samuel Houser presided over last week's National Shade Tree Conference, has established a central diagnostic laboratory for elm blight. Twigs of suspected trees are sent there. Forty hours produce a definite test. A Cleveland elm was the first U. S. tree discovered to be infected. That was in 1930. Now the elms of all the Northeastern States are threatened. In New York and New Jersey 234 elms have been pruned, 126 cut down and burned. The possibility of American elms disappearing on account of the blight strengthened Dr. Elmer Drew Merrill's argument for a botanical exploration of Northern Japan, China, Korea and Manchukuo. Dr. Merrill, who is director-in-chief of the New York Botanical Garden, called attention to the fact that native trees of eastern Asia and eastern North America are closely related.*Reason: geological and climatic changes affected both regions at about the same time throughout the ages. The elm is one of the trees whose Asiatic cousins may be resistant to blight and warrant transplanting to the U. S.

*Another point: the only large areas where trees develop autumnal colors are northeastern U. S., northeastern Asia, northwestern Europe.

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