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Is Dutch Elm Disease Still a Threat?

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What is Dutch Elm Disease?
It is a very destructive plant disease caused by a fungus which is most often spread by the bark beetle. Even though it is referred to as the Dutch Elm Disease, it is not specific to only one type of tree. It gets its name from a Dutch scientist who first discovered it in the early 1920's. It is believed that the fungus disease actually began in Asia, and was accidentally spread first to Europe in the early 1920's and then to North America a decade later. The tree disease is responsible for destroying millions of trees in both North America and Europe.

How Does Dutch Elm Disease Work?
Problems begin when the fungus attacks the tree's vascular system and prohibits water and nutrients from being transported throughout the tree, and the tree eventually is depleted of nutrients. While in the tree, the fungus reproduces spores that spread the disease throughout the tree's vascular system. As a result, the tree's branches finally begin to wither. In time, the elm tree will die.

The first sign that a tree has been infected with Dutch Elm Disease is when the leaves of an upper tree branch begin to wither and turn yellow during the summer months. As the disease progresses, the tree branches will continue to lose their leaves and the branches will begin to die. Ultimately, the roots will die.

How Does Dutch Elm Disease Spread?
The disease can be spread in one of three ways.

The most common way the disease is spread is through several species of bark beetles: the European elm bark beetle, the banded elm bark beetle, and the elm bark beetle. This insect is about the size of a piece of rice. It breeds and feeds in elm wood. During their life cycle, the beetle comes in contact with the Dutch Elm fungus spores. The spores stick to the beetles and are then spread to the Elm tree.

Another way the disease is spread is through root grafting. Elm trees that grow in close proximity to each other can join at their roots and begin sharing water and nutrients. When one elm tree becomes infected, the fungus will eventually spread from one tree to the other.

In addition, the disease can also be spread by humans. Elm Bark Beetles live in elm wood that is used for firewood. When the firewood is transported to other areas, the beetles can migrate to the neighborhood elm trees and continue to spread the disease.

The threat of Dutch Elm Disease to American Elm trees is still a serious concern today. There is no cure.
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