Dutch elm disease
Dutch elm disease is an aggressive disease of American elm trees. The fungus that causes the disease moves from tree to tree via elm bark beetles. As the beetles tunnel in to lay eggs, the fungus enters the plants' water-conducting system. Once inside the tree, the fungus begins to plug the vascular system. As a result, leaves wilt and the affected tree dies within a few months to a year.
Several steps can be taken to determine if a tree elm has Dutch elm. First, identify the elm in question. Most elm trees in Colorado are Siberian elm, which are not susceptible to Dutch elm disease. Only American elm is susceptible. Next, if wilting symptoms are evident, obtain samples of the twigs in the area of the tree that leaf wilting occurs. Twigs should be one to two inches in diameter. Peel back the thin layer of bark to view the wood just underneath. If dark discoloration or streaks run the length of the twig, Dutch elm disease is suspect. Finally, send samples to a diagnostic clinic or city forester for laboratory analysis.
An American elm diagnosed with Dutch elm disease, must be removed. This practice helps slow the spread of the fungus to healthy trees. In locations where American elms are growing next to each other, it is important to trench roots to prevent the spread of the disease from one tree to another through root grafts.
Injection of fungicides into healthy American elms can help prevent possible Dutch elm disease infection. Control of the bark beetle vector is a last step in helping to prevent the spread of this devastating disease.
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Updated Friday, April 19, 2013