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Are Your Trees Susceptible to Dutch Elm Disease?

 

Dutch Elm Disease is affecting trees all over the country, including one family in Portland, Oregon. Alyssa Gregg, a 15-year resident of Ladd’s Addition, was flabbergasted to find out that her trees, which were infected with Dutch Elm disease, would cost $4,000 to remove.

Are Your Trees Susceptible to Dutch Elm DiseaseIt wasn’t an isolated incident either. Last year her neighbor lost a tree to the same disease. Gregg wasn’t as much surprised by the fact that the tree was infected, as an assessment last year forecasted as much, but she thought the city would fit the bill. Now there’s a dispute, and there’s likely no happy ending in site for this local resident.

Dutch Elm disease is caused by a fungus and is highly lethal to American and European elms. The symptom of Dutch elm disease is flagging, a wilting and browning of leaves, usually on a single branch or portion of the canopy. According to the City of Portland’s website, susceptible species include American elms, Dutch elms, English elms, Wych elms, Camperdown elms and smoothleaf elms. Fungicide can be injected into elm trees as a preventative treatment, but a certified arborist must supervise the fungicide injection procedure.

According to APS, The Ophiostoma species that cause Dutch elm disease grow and reproduce only within elms. At times they are parasites, feeding on living tissue of the elm tree; at other times they are saprophytes, getting nourishment from dead elm tissue.

Dutch Elm disease spreads in one of two ways.

  1. Beetles spread Dutch elm disease: Beetle infections generally start in the 2 to 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 through the tree. The characteristic stain on the xylem 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 graft 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.

Today, some communities maintain active programs to manage Dutch elm disease because they have found that it is cheaper to manage the disease than to remove the large dead trees that it leaves behind.

Here are two options:

  • Chemical: More recently, fungicides have been injected into trees infected by or at risk of infection by the Dutch elm disease pathogens. These systemic chemicals are most effective if they are used to prevent new infections or to prevent the movement of the fungi into parts of a tree that are not yet colonized.
  • Breeding for Resistance: The long-term solution to Dutch elm disease lies in the development of disease-resistant cultivars of elms. Several Asian elm species have moderate to high resistance, and breeding programs in both Europe and the U.S. have introduced resistance from these species into native elm species.

Don’t immediately assume you’re dealing with Dutch Elm disease. It’s always important to get an expert in tree surgery to come take a look at the situation. They’re able to distinguish Dutch Elm disease from look alike problems, such as:

Drought
Drought symptoms in an elm usually shows up as sporadic yellowing flat leaves that are dispersed throughout the tree canopy. Whereas Dutch elm disease causes the leaves to curl and the dieback is usually thorough in one or more section of the tree.

Leaf miner
If the lower leaves are visible, you will see flat leaves that have small whitish spots or if the infestation is severe, the leaves will take on a tan appearance.

Broken branch
Look for strange branch angles which are a good indicator of broken branches. Broken branches will often hang down and the symptoms on the branch will not progress. The use of binoculars can be a good tool to distinguish the difference.

Again, make sure not to self-diagnose. As much as you think you may know, you’re most likely not the expert. Sure, it will cost a few bucks, but if you go through the expensive process of removing a tree when it doesn’t need to be removed, you can actually cost yourself more. Let the experts handle the diagnostics.

If you don’t know what kind of Elm you have on your property or in your neighborhood, an arborist consultation is a great way to identify and prevent more losses of these beautiful trees. If you have an Elm that has been killed or affected by DED, another important note is the proper disposal of material. All brush/wood that can be chipped should be. Other methods of disposal are burning, burying, and debarking. Tree material infected with Dutch Elm disease should not be transported, as it can spread the disease to areas not affected.

Now to come full circle, Gregg was told if the dying trees weren’t removed in 15 days a lien would be put on her home. She said she wish she knew this was a possibility, but she wasn’t informed. If she knew, she’d have more than 15 days to come up with the substantial $4,000 figure. To make matters worse for Gregg, not only does she need to remove the trees, but City code requires her to replace them, and that can cost $300 apiece. It sure looks like she’s going to need a tree surgeon in Portland, Oregon, to come and get the job done.