Dutch elm disease is caused by a fungus which attacks only elm trees. The beautiful American elm shade and boulevard tree is especially susceptible. The disease is spread from tree to tree by bark beetles. They carry the fungus on their body and infect the tree when feeding on it. The disease can also be spread from one tree to another by root grafts. The disease has become fairly common.

The first signs of the disease are a yellowing and wilting of the leaves (flagging) on one or more branches in the upper areas of the tree. The disease progresses rapidly and often kills the tree within one or two years. When diseased branches are cut, and the bark peeled back, brown streaks can be seen in the sapwood. These streaks indicate the presence of a wilt disease. Positive diagnosis of Dutch elm disease requires an analysis of the diseased branches in a laboratory. For sampling, six diseased but alive twigs, about 6 to 8 inches long and one inch in diameter should be cut and identified with the tree. These samples should be submitted to a diagnostic lab through your county agent.

The best method of controlling the disease is through a good sanitation program. Diseased trees must be detected, removed, and the wood destroyed or debarked. Dead and dying elm branches or trees, whether diseased or not, must be removed, as these are the breeding sites of bark beetles. Don't bring elm firewood into your city, town or farmstead unless the bark has been removed. Fungicides are not recommended except for valuable elm trees in high risk areas.

This page was last updated May 2003

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