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# Bow can I teU If an American elm bas DED? Look for leaves that are wilting or yellow and which eventually turn brown. Wilting and leaf color change are symptoms of OED that occur during the spring and summer, but usually start to appear one month after trees leaf out in the spring. Leaves most affected appear at the end oflarge branches. Dead branches without leaves may indicate previous year's mortality from OED. In some communities, disease experts make routine elm examinations for OED symptoms. Bow and why do experts evaluate DED symptoms? Experts examine each tree and estimate the percent ofleaves with symptoms and relate this percentage to where symptoms are located. This determines how much disease is in the tree, and it can also indicate whether the fungus infected the tree through joined roots or bark beetle wounds. The most appropriate OED management tactics are based on the amount of disease present. The amount of disease can be described simply as being either minor or major. What are minor amounts of DED In elms and can these elms be treated? Elms with minor OED have few symptoms (less than 10 percent of all leaves) USlllllly located in only one large branch. OED may be eliminated from these trees by pruning out diseased branches and/or injecting chemical fungicide into the base of the trees. If left untreated, however, the amount of disease will increase. What are major amounts ofDED In elms and can these elms be treated? Elms with major OED usually have more than 10 percent of all leaves or more than one large branch showing symptoms. Unfortunately trees with major amounts of disease cannot be effectively pruned. Fungicide injection is unlikely to be effective to stop an infection that has occurred through joined roots or which has affected a large portion of the branches. Elms with major amounts of disease will eventually die from the disease, and provide habitat for beetles and fungi that can infect healthy trees. Elms with major OED should be removed as soon as possible. This removal of diseased elms is called sanitation and is crucial to eliminate the spread of both the elm bark beetles and fungus to healthy neighboring elms. Is there hope for the American elm? Yes. If communities practice good sanitation (removal of dead trees), many existing elms will escape OED infection. It is also possible to prune diseased branches and inject individual high-value elms with fungicides to treat and protect them from OED infection. Also, scientists are now testing American elms that may be tolerant or resistant to OED. Combining all of these management tactics provides promise for the continued presence of American elms in our cities and parks. Where can I get more Information abont DED? The recent publication "How to IdentifY and Manage Dutch Elm Disease" is now available on the Internet at http://willow.ncfes.umn.edulht_dedlht_ded.htm. Information is also available from your city forester, tree care companies, your local Cooperative Extension Service, or the Forest Service offices listed below. Photographs pl'O\lided by Dr. R. Jay Stipes, Virginia Polytechnic Institute and State University. m For additional information, contact: Alan Iskra USDA Forest Service 180 Canfield Street Morgantown, WV 26505 Phone (304) 285-1553 Linda Haugen USDA Forest Service 1992 Folwell Avenue SI. Paul, MN 55108 hltp:llwillow.ncfes.umn.edu July 1999