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Tree Disease - Dutch Elm Disease
Dutch Elm Disease is caused by an aggressive fungus (Ophiostoma-ulmi) that kills elms regardless of their health. It is considered the most costly shade tree disease ever and will remain active in a community as long as there are susceptible trees. The fungus invades the water transporting vessels and produces toxins to which the tree reacts. In defense to the toxins the tree produces gums and internal growths designed to block the advance of the fungus. The combination of the toxins and the defense mechanisms of the tree inhibit water flow to the crown, which causes wilting and tree death.
Dutch Elm Disease
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Sanitation is the most important tool for controlling Dutch Elm Disease on a community-wide basis. It involves identification and removal of diseased elms. Such practices eliminate beetle breeding sites and reduce the number of disease carrying beetles.
The goal when protecting elms from the Dutch Elm Disease fungus is to evenly and completely distribute a fungicide chemical throughout the entire canopy of the tree.
What is the cause of Dutch Elm Disease
Dutch Elm Disease is caused by an aggressive fungus (Ophiostoma-ulmi) that kills elms regardless of their health. It is considered the most costly shade tree disease ever and will remain active in a community as long as there are susceptible trees. The fungus invades the water transporting vessels and produces toxins to which the tree reacts. In defense to the toxins the tree produces gums and internal growths designed to block the advance of the fungus. The combination of the toxins and the defense mechanisms of the tree inhibit water flow to the crown, which causes wilting and tree death.
Female elm bark beetles lay their eggs beneath the bark of dead and dying elm trees. If the elm is infected with Dutch Elm Disease the newly hatched beetles will emerge from the tree carrying the deadly fungus on their bodies. The beetles fly to healthy trees to feed on 2-4 year old branches and thereby spread the disease.
Dutch Elm Disease symptoms begin to develop 4-6 weeks after infection. The first noticeable symptom that results from the fungal occupation of the water conducting vessels is wilting or “flagging” of one or more branches, usually starting at the branch tip. Leaves on infected branches turn dull green to yellow, curl, and become dry and brittle. As the infection spreads the wood beneath the bark displays a brown discoloration.
2.Remove infected branches from trees (if identified in time) or remove entire trees, immediately, in order to halt further spread of the disease throughout the neighborhood.
3.Isolate infected trees from nearby healthy trees by soil trenching, which prevents spread of the disease via root grafting.
4.Protect valuable remaining elms with the use of an approved Dutch Elm disease fungicide.
What can I do if my tree is already infected?
Most infected elms cannot be saved. In rare cases, if the fungus has not moved into the root system, physically cutting out the infected portions of the tree, with a process called tracing, can save the elm.
Sanitation
Sanitation is the most important tool for controlling Dutch Elm Disease on a community-wide basis. It involves identification and removal of diseased elms. Such practices eliminate beetle breeding sites and reduce the number of disease carrying beetles.
How can I protect my Elm tree?
The goal when protecting elms from the Dutch Elm Disease fungus is to evenly and completely distribute a fungicide chemical throughout the entire canopy of the tree.
At A&A we will provide a no-obligation visit to discuss the best treatment for your application.
The Basic Facts
What is the cause of Dutch Elm Disease
Dutch Elm Disease is caused by an aggressive fungus (Ophiostoma-ulmi) that kills elms regardless of their health. It is considered the most costly shade tree disease ever and will remain active in a community as long as there are susceptible trees. The fungus invades the water transporting vessels and produces toxins to which the tree reacts. In defense to the toxins the tree produces gums and internal growths designed to block the advance of the fungus. The combination of the toxins and the defense mechanisms of the tree inhibit water flow to the crown, which causes wilting and tree death.
How does Dutch Elm Disease spread?
Female elm bark beetles lay their eggs beneath the bark of dead and dying elm trees. If the elm is infected with Dutch Elm Disease the newly hatched beetles will emerge from the tree carrying the deadly fungus on their bodies. The beetles fly to healthy trees to feed on 2-4 year old branches and thereby spread the disease.
- 2-3 generations of elm bark beetles hatch each year
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Thousands of beetles may hatch from a single tree
Besides beetle transmission, Dutch Elm Disease may also spread through grafted roots. When elms grow in close proximity to each other, their roots can come into contact and graft together. This common root system provides the fungus with a pathway to spread through an entire stand of healthy elms very quickly.
What are the symptoms of Dutch Elm Disease?
Dutch Elm Disease symptoms begin to develop 4-6 weeks after infection. The first noticeable symptom that results from the fungal occupation of the water conducting vessels is wilting or “flagging” of one or more branches, usually starting at the branch tip. Leaves on infected branches turn dull green to yellow, curl, and become dry and brittle. As the infection spreads the wood beneath the bark displays a brown discoloration.
Management and Research
Cities such as Minneapolis, Edina, Richfield, Minnetonka, St. Louis Park and Bloomington are still home to large inventories of American elm trees. In fact, the Twin Cities boasts one of the largest American elm populations in the country.
For approximately 50 years Dutch Elm disease has devastated unprotected elm populations across the United States, spreading westward from its origins on the East Coast. However, with the development of responsive community programs and effective fungicidal injection treatments, the disease has been brought under reasonable control. But it never really went away.
Dutch elm disease kills elms regardless of their health. It is considered the most costly shade tree disease ever and will remain active in a community as long as there are susceptible trees.
To properly manage Dutch elm disease, four steps are generally required.
1.Identify the disease by the "flagging", or wilting of leaves typically located at the ends of isolated branches in the canopy. The disease moves down the limb and then into the main stem.
2.Remove infected branches from trees (if identified in time) or remove entire trees, immediately, in order to halt further spread of the disease throughout the neighborhood.
3.Isolate infected trees from nearby healthy trees by soil trenching, which prevents spread of the disease via root grafting.
4.Protect valuable remaining elms with the use of an approved Dutch Elm disease fungicide.
