Dutch Elm disease can kill an older tree in less than a year, however, some younger and healthier trees can last a few years. American elms are commonly infected in two ways: elm bark beetles that transfer the disease from infected to healthy trees, and fungi that are transmitted through root grafts. This is an aggressive disease that is almost always fatal to the host tree once it becomes established.
Shortly after infection an elms tree’s leaves will begin wilting from the upper portion of the tree. The leaves will change from yellow to brown and eventually die and fall off the tree. There will also be a discoloration of the wood under the bark indicated by dark streaks.
Before an infected tree is removed, a trench is often made between the infected tree and the healthy elm that is going to be treated for the prevention of the Dutch Elm disease. This will help to prevent the transmission of the disease through the roots. If an elm is already infected, branches with symptoms will need to be pruned and the sapwood inspected for the dark streaks/staining with more branches removed. With an infected elm, the success of the treatment will depend on how badly the tree has been infected.
What To Expect After Treatment
For a healthy elm that has shown no symptoms of the disease, the chemical Arbotect will offer protection for three years. Arbotect offers no protection from root transmissions, however. For an elm that already has the disease, tree recovery will be dependent upon the severity of the Dutch Elm disease at the time of the eradicative pruning and a different chemical is applied that is effective for one year only.