|Infected English Elm|
|Dutch Elm Beetle|
There are now three known species recognized as Ascomycete Fungi which are causing the destruction of the Elm trees in many areas of the world. The Native Elm Bark Beetle, the European and the Banded Elm Bark Beetle have found a solid foot hold in the Elm trees and bring their destruction as they continue to migrate and destroy all in their path.
As the disease spreads throughout the tree, the trees natural defense mechanism kicks in to destroy the virus that has infected it. However, in doing so, the tree is inadvertently killing itself off as it blocks the needed nutrients from reaching sections of the tree and as those areas begin to fail, the whole eco~system of the tree fails and death is its ultimate sacrifice for survival.
A tree will react by trying to block its own xylem with gum and tyloses, a kind of a growth that extends on the xylem cell's walls. Now as the xylem delivers water and nutrients to the rest of the tree, these "blocks", prevent them from travelling up the trunk resulting in the tree's demise.
DED was first introduced into North America in or around 1928 in a shipment of logs believed to have come from the Netherlands, which were destined as Veneer for an Ohio furniture industry. The disease slowly spread west and south completely destroying whole forest growths of Elm trees in its wake.
During the Second World War, DED was introduced to Canada and found its way to Ontario in 1967, Manitoba by 1975 and Saskatchewan by '81, British Columbia has recorded great success in their DED removal, while Alberta remains DED free to this day. Of all the major cities to try and find a solution for this growing problem, Toronto has been hit the hardest, losing almost 80% of her Elm trees to DED. On another interesting note, Winnipeg has the honour of being home to the largest surviving urban forest with close to over 200,000 Elm trees remaining free of the disease.
If your wondering if your trees are suffering from Dutch Elm Disease, some good measures to pay attention to are the upper branches, the leaves will usually turn yellow, brown as they begin to wither. This usually begins to occur in late June to early July and will progressively kill off other branches as the tree begins to die from starvation as the roots suffer without the nutrients from the leaves. You may also notice small holes, the diameter of a pencil lead and/or sawdust around the bark, may be an indicator that the tree has beetles burrowing within.
To solve the situation can become costly to some and not feasible to others. One can have the tree cut, removed and burned to avoid further contamination. Chemicals such as insectides DDT and Dieldrin offer some a solution, however, this is not an option I would recommend as you must think of the birds and animals that have to suffer the poison produced from such methods, one solution does not always bode well with the outcome. Dead branches and trees should be removed from the area as they are perfect breeding grounds for Bark Beetles. Please remember to keep your healthy Elm trees well watered to help prevent invasion.
DED is spread by a fungus, not the beetle itself and there are three ways in which it is transmitted. One method is by beetle vectors which carries the fungus from tree to tree; through the connection of healthy tree roots with those that are infected and by pruning healthy trees with blades that have been used to cut diseased trees. One could say its almost like a zombie disease amongst the trees. It is imperative that you should be very careful in what companies you use to prune your trees and to make sure you use reliable, professional arborists who understand the necessary procedures to process trees so that your remaining trees remain alive and healthy.