Dutch Elm Disease Dutch Elm disease is caused by the fungus ceratocystis ulmi. This fungus invades and grows in the water conducting vessels the elms. In an effort to protect itself, the host tree produces tylosis and gums which plug the vessels, preventing water uptake. This causes the tree to wilt and die. All species of elms native to North America are susceptible to Dutch Elm Disease. Some elms such as the Siberian Elm are less susceptible than others, but none are immune. INFECTION The Dutch Elm fungus is spread by one of two ways, either by elm bark beetles or through root grafts. Beetles - In Minnesota, the fungus is spread by either the native elm bark beetle which is more prevalent in the Northern part of the sate, or by the European elm bark beetle which is the primary vector in the Southern portion of the state, including the Twin Cities. Both beetles use dead or dying elms for breeding. Beetle breeding tunnels in infected wood become filled with fungus spores which then contaminate beetles. Contaminated beetles then fly to healthy elms to feed on their branches. As they feed through the bark, they transfer the spores into the vascular system of the tree. The tree responds by plugging its vessels to stop the spread. This defense results in wilting of one or more of the upper branches. If caught in time, infected limbs can be removed to stop the spread of the disease, but this should be done by a professional who can examine the wood to be sure enough has been removed. Tree Inspectors are trained in this process. Fungicides when properly administrated can protect healthy elms from infection and can cure trees in an early stage of beetle infection. Dead or dying elms should be removed as soon as possible to eliminate breeding sites for other beetles. Root grafts -  The fungus can also be spread through roots that are naturally fused together between infected and uninfectected trees. This type of transmission of the fungus only occurs in about ten percent of new infections. To reduce the chance of infection through root grafts, mechanical trenching can be used to break the bond between trees. Another option is to treat the bonded area with the chemical Vapam. Death of an elm through root graft transmition is much more rapid usually lasting only a few weeks.
Licensed Tree Service and ISA Certified Arborist serving the greater twin cities and central Minnesota, including: Minneapolis, St.Louis Park, Coon Rapids, Edina, Richfield, Bloomington, St.Paul, and more.