Answer: Although there is no known American elm variety that can be called entirely immune to Dutch elm disease, the following have shown strong resistance to the disease: the Princeton Elm, the American Liberty "multi-clone," and Independence, which is one of the cultivars in the American Liberty multi-clone. Two additional American elms, Valley Forge and New Harmony, have exhibited high tolerance to the disease. Consult with your local nursery to see if they can get the trees for you, or contact the Elm Research Institute, P.O. Box 150, Westmoreland, NH 03467, 1-800-FOR-ELMS.
Up to 100 million American elms succumbed to Dutch elm disease (DED) since the beetle-borne fungus first appeared in elms in the U.S. in the 1930s. The fungus infects the vascular (water-conducting) system of the tree, clogging it and preventing water movement to the crown. The first symptom is often dieback of individual branches from the tip inward toward the trunk, called "flagging."
The special features of the American elm -- a stately, vase-shaped, fast-growing, pollution-tolerant tree -- led to its being planted in rows down countless suburban streets. Unfortunately, this pattern of planting also led to its demise. Not only could the elm bark beetles responsible for spreading the disease easily travel from tree to tree, but the disease also spread via the natural root grafts that occurs between adjacent trees.
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