Dutch elm disease is a fungus called Ophiostoma Novo-ulmi. This fungus grows only in elms – like American elm and Siberian elm trees. The disease is spread from infected trees to healthy trees most commonly on the elm bark beetle, Scolytus multistriatus. It can also pass from one tree to another through root grafts, a situation where a tree’s roots fuse underground with another tree of the same species.
Although there are several ways to treat for Dutch elm disease, the best method is to prevent the fungus from infecting your tree. One application of Arbotect® fungicide can protect a tree for up to three years. Arbotect® gives greater than 99% success over 3 years when applied properly. Arbotect® does not work if the tree already is infected with Dutch elm disease or the disease fungus enters the tree through root grafts.
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Dutch Elm Disease Treatment Option 1
Protecting with Arbotect®
The purpose of preventive macro-infusion with Arbotect® is to provide even and complete distribution of the fungicide a chemical compound designed to kill or stop fungal spores from germinating and creating a fungal infectionthe colonization of a tree by a pathogen (not insect) as in oak wilt or Dutch elm disease.. throughout the 2-4 year old twigs were the beetles feed. Trees should be treated after the leaves have fully enlarged or after the seeds have dropped. The treatments can be administered until there is fall color present in the canopythe leaf area of a tree.. Arbotect® does not work if the tree already is infected with Dutch elm disease.
Diseased elms should not be treated with Arbotect®. Our experience is that Arbotect® will mask the symptoms of the disease for 1-3 seasons before the tree dies. Arbotect® does not prevent infections that grow through root grafts, so in situations where this is a concern , install a trench and wait until the following season to make sure the tree is healthy before protecting with Arbotect®. As a preventive treatment this process gives highly predictable results.
Dutch Elm Disease Treatment Option 2
Saving infected elms with tracinga method of removing a diseased section of a tree in order to stop its spread within the tree. Often done on elms to stop the spread of Dutch elm disease.
Tracinga method of removing a diseased section of a tree in order to stop its spread within the tree. Often done on elms to stop the spread of Dutch elm disease. is a method of saving recently infected elms, where diseased portions of the tree are removed. Although this process can be effective, only trained professionals should trace elms. Only the earliest stages of Dutch elm disease can be stopped by using this method, and it still requires the use of fungicides. The most effective method of treating individual trees for Dutch elm disease remains to be preventative Arbotect® applications. Contact a tree geek for more information.
Dutch Elm Disease Treatment Option 3
Root graftan area where two roots touch underground, fusing tissues to increase water and nutrient uptake. disruption the cutting of root grafts to stop the progression of diseases spread via root systems.
Root graftan area where two roots touch underground, fusing tissues to increase water and nutrient uptake. disruptions involve physically cutting the roots shared by healthy and diseased trees through a process called trenching. This is most reliably accomplished mechanically with either a trencher or vibratory plow. Remove the diseased elm only after common roots have been disrupted. Contact a tree geek for more information on disrupting root grafts.
How Is It Spread?
Dutch elm disease spreads from tree to tree in two ways.
1. Beetle spread of Dutch elm disease
Beetle infections generally start in the 2-4 year old twigs, where the beetle feeds and mates. The fungus rubs off the beetle and begins to grow in the tree in a downward pattern. Once it has reached the root flares, the fungus can spread to other trees through root grafts, as well as throught the tree. The characteristic stain on the xylemthe principal waterconducting tissue that transports water and dissolved minerals from the roots to the rest of the plant. It also is the chief supporting tissue of plants. of an elm infected with Dutch elm disease is caused by the tree producing gum-like substances, called tyloses, in an attempt to stop the spread of the disease. These tyloses cause the tree to wilt and die.
2. Root graftan area where two roots touch underground, fusing tissues to increase water and nutrient uptake. spread of Dutch elm disease
The other method of disease transmission between elms is through grafted roots. When elms are growing near each other their roots come in contact in the soil and graft together. The Dutch elm disease fungus can pass from diseased to healthy trees through these grafted roots.
The first evidence of Dutch elm disease is wilting the slow or rapid collapse of leaves, branches or entire plants. or “flagginglimbs in trees showing symptoms of a disease, usually Dutch elm disease, and typically affecting one small branch or a group of branches.,” leaves on the infected branches turning dull green to yellow and curl, finally becoming dry, brittle, and brown. The symptoms progress down the limb and eventually throughout the entire tree. If bark is peeling off the infected wood, the water conducting vessels will reveal the brownish stainingevidence of a tree’s chemical reaction to a fungus. In Dutch elm disease and oak wilt, staining usually indicates plugged xylem vessels. caused by tyloses.
Understanding the Dutch elm fungus and how it grows makes diagnosing this disease easier. A few key distinctions will help in accurately making sure that you are in fact dealing with this dreaded disease.
1. Leaves on infected trees are almost always curled or wilted looking. They often drop off. Leaves that are flat and shiny are common in the late summer and are usually caused by branch senescencethe aging of trees, often used to describe trees in decline the slow death of a tree, often seen as reduction in growth, dead limbs in the top of the tree, or leaves that change from their usual green color. due to their old age..
2. Dutch elm disease symptoms progress as the fungus grows in the tree. Thus, there is a pattern of leaf death outside the tree that reflects the fungus growth inside the tree.
3. Check under the bark close to where there are external leaf symptoms. Dutch elm disease always causes the water conducting vessels to turn a dark brown. Finding this discoloration along with wilting the slow or rapid collapse of leaves, branches or entire plants. leaves is a very good indicator that Dutch elm disease is present. Use a chisel and a hammer to open a hole in the bark to check for the discoloration.
4. If you are unsure if your elm has Dutch elm disease send photos to a tree geek. Use our tree diagnosis form.
Distinguishing Dutch elm from look-alike problems
Drought symptoms in an elm usually shows up as sporadic yellowing flat leaves that are dispersed throughout the tree canopythe leaf area of a tree.. Whereas Dutch elm disease causes the leaves to curl and the diebacka condition where dead branches usually start at the top of the tree and work their way down. is usually thorough in one or more section of the tree.
If the lower leaves are visible, you will see flat leaves that have small whitish spots or if the infestationthe invasion of a tree by an insect. is sever, the leaves will take on a tan appearance.
Look for strange branch angles which are a good indicator of broken branches. Broken branches often will hang down and the symptoms on the branch will not progress. The use of binoculars can be a good tool to distinguish the difference.
Drought, leaf miner
Spring through summer
Risk of Spreading