Minnesota Dutch elm disease or DED was first discovered in the Netherlands around 1919. It quickly spread across Europe. DED made its first presence in the United States in the early 1930’s. Ohio reported the first fungus disease in imported logs from Europe which contained not only the fungus but the European elm bark beetle as well. Minnesota Dutch elm diseaseis a fungus Ceratocystis ulmi that invades the tree which infects the Elm tree. Once introduced into the elm tree, by way of the elms’ vessels, growths or tylosis and gums are produced. This foreign production, in combination with the fungus plugs or inhibits the water vessels from supplying the needed water and nutrients to the feeding system.
Without the proper functioning vascular system the tree will wilt and die. The vascular system of a tree performs much like our circulatory system. The system delivers from the roots needed water and minerals and through the process of osmosis, distributes the carbohydrates and sugars caused by photosynthesis throughout the tree. When the vascular system is compromised by the introduction of the fungus the entire will become diseased. The transmission of the fungal growth of Minnesota Dutch elm disease is caused either by the bark beetle or from root grafting. This is a natural occurrence when trees are growing in an area less than thirty feet from another elm. For larger elm trees root grafting can occur within sixty of spacing.
When an elm tree is infected by root grafting rather than by beetle infestation the death of the tree is far more rapid. The first Dutch elm disease symptoms visible are the leaves will begin wilt ant to turn yellow and then turn to a brown. The beginning or the infected area will show if infected by a bark beetle. This is the onset of the first system. If the fungus was introduced by way of root grafting from an infected tree, the wilting and leaf colors changing to the yellow and brown leaves may begin to show on the side of the tree crown infected. There can be more than one area showing signs of infection depending on how much involvement of the roots has been infected. This process of infection will travel up from the bottom of the tree to the very top. If the fungal infection of Dutch elm disease has been introduced by the bark beetle it will appear at the end of the specific branches of the tree infected and proceed downwards toward the crown or the tree. The European elm bark beetle larval stage is under the bark of the dead or dying elm wood. A new generation of European elm bark beetle descends upon the elm trees in the early spring.
To manage and protect the elm trees from Minnesota Dutch elm disease, prevention is a critical and necessary program. Within the prevention program, action areas require the initial detection of Dutch elm disease. There must first be early inspection for the detection of Dutch elm disease. Second, is isolation, to disrupt the root grafting between the healthy elm trees and those that are infected. Third, removal – swift elimination of all the dead and dying elm trees and woodpile logs diseased with Dutch elm disease. Fourth, the disposal of the complete and total destruction by means of burning, chipping, debarking, or burying all elm tree byproducts, i.e. bark, logs in woodpiles.
These four preventative measures are a key function to the management of Dutch elm disease. This greatly reduces the spread of the disease and allows for early pruning of infected branches as an effective management technique to preserve existing trees. This course of containment would allow for the use of injecting fungicides and spraying of insecticides. Eliminating the spread of the disease by controlling the source, the elm bark beetle greatly reduces the spread of the disease. One elm the size for a fireplace log can produce 1,800 elm bark beetles. It is no wonder why containment is the only measure to eliminate Minnesota Dutch elm disease.