Elm trees are majestic and beloved shade trees. Elms grow well in the most severe settings, they transplant easily and grow rapidly when planted in favorable conditions. Elm trees prefer full sun but will tolerate moderate shade. They grow best in nutrient-rich, moist, well-drained soil but can thrive in less-than-perfect soil conditions. Although it's a hardy tree, the Elm is susceptible to a few destructive and sometimes deadly diseases.
Dutch Elm Disease
Considered the most devastating shade tree disease, Dutch elm disease has taken a high toll on elm trees throughout the world. Dutch elm disease is caused by a fungus that rapidly spreads through the tree. The fungus blocks the vascular system of the tree, which stops water and minerals from reaching the leaves and branches. The leaves whither and the tree dies. Younger trees will die quickly; older trees can survive for a year or two before dying.
Controlling and treating Dutch Elm disease is difficult. A treatment called ELMguard has been used to help prevent and stop the spread of Dutch elm disease. Small holes are drilled into the tree and ELMguard is injected into the holes; a wax sealer closes the holes. It does not provide 100 percent protection from the disease, but it's helping in the prevention and spread of Dutch elm disease.
Anthracnose is a fungus that attacks elm trees. The disease will cause the defoliation of the elm tree. Damage usually occurs after cool, damp weather during bud break. One sign of Anthracnose is repeated early leaf loss which, if occurring several years in a row, will cause the elm tree to weaken and leave it susceptible to borer attacks and injury. Buds and twigs may die and premature leaf drop begins, which causes a decrease of shade and an unhealthy-looking tree.
Preventative measures will reduce the chance of Anthracnose greatly. Rake up and burn infected leaves. Prune the tree and remove dead twigs and branches and burn them. Control Anthracnose by spraying a fungicide containing mancozeb at the budswell and over leaves twice during leaf expansion time. Follow instructions on the label. Stopping anthracnose is imperative as it is often fatal to the tree.
Verticillium wilt is a serious vascular disease caused by the fungi Verticillium albo-atrum and Verticillium dahliae. Symptoms of this disease are leaf wilt and die-back of branches. Often one side of the elm tree remains healthy while the other side is affected by the disease. Verticillium wilt can last for years, sometimes going into remission and then coming back again. It can progress quickly and kill the tree with in a year or two.
Fungicides are not effective in controlling Verticillium wilt. Pruning out the infected branches and burning them helps limit the effects of the infection. Healthy trees are less susceptible to the disease, so fertilize trees regularly and keep them properly watered.