Protecting Elm Trees Against Dutch Elm Disease (DED)

Elm trees were once the pride of New York cities and towns, with their over-100 feet heights, wide trunks and overarching spreads. Since the 1950s, however, millions of Elm trees have succumbed to Dutch Elm Disease, a fungal infection that originated in Asia but was first described in Holland in 1921 (hence the name). It began appearing in elms in the United States in the 1930s.

The disease is carried from tree to tree either by bark beetles or directly through the merged roots of two or more adjacent trees. Once a tree if infected it has no chance for survival. As a tree fights the infection, because of internal scarring, it loses the ability to transport nutrients and water through its trunks and slowly dies in a few months.

Although there is not much that can be done once an elm tree is infected, there are preventative measures that can be taken to protect these magnificent trees.

Quick Removal of Diseased Trees and Branches

It is important to remove infected trees as quickly as possible to reduce the breeding sites for the elm bark beetle and contain its spread. If the wood from infected trees is being stored for firewood, the bark must be removed from the pieces and destroyed. Branches with flagging symptoms should be removed with the cut made 5-10 feet behind any visual symptoms. Speak to your Almstead arborist about removing trees and branches that have possibly been infected with DED.

Inoculating Elm trees against DED

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We have found that inoculating Elm trees as the best way of preventing Dutch elm disease. Over the past few years, Almstead has employed this method to successfully treat and prevent infection in hundreds of elm trees in our area.

We select multiple injection points in the root system of a tree and circulate a fungicide mixture simultaneously to all entry points using a pump. The concentration of the mixture is calculated based on the circumference of the trunk as well as the height and spread of the tree.

The tree does the rest. It takes in the control solution to all its branches. Depending on the size of the Elm, this can take over 5 hours. The treatment is 99.5% effective and will last for 2-3 years depending on the size and condition of the tree, at which point it will have to be repeated.

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For more information on Dutch Elm Disease and other pathogens that commonly affect plant life in our region, we recommend visiting plantclinic.cornell.edu/factsheets.html