Symptoms of a late summer infection include wilting and yellowing of leaves, or premature defoliation of the tree in fall. In all cases, leaf symptoms are accompanied by brown streaking of the sapwood. The wood just below the bark that should be clear white will have distinct brown lines or bands. Trees that fail to leaf out in the spring may also have Dutch elm disease. The only suitable action to take in the case of an infected tree is total removal of the tree.
All wood is burned or burried, with the stump also removed and treated similarly.
Two other diseases resemble Dutch elm disease so closely that laboratory analysis is the only way to decide which disease is effecting the tree in question. The symptoms of Dothiorella and Verticillum wilt look almost exactly like those of Dutch elm disease. Verticillum wilt is caused by a soil-borne fungus, and can appear on elms, maples, and many other different trees and shrubs. Trees infected with Dothiorella can be pruned to remove the infection, however pruning is not usually effective in controlling Verticillum. It is because the symptoms of these diseases are so similar that twig samples are taken from infected trees.