Dutch Elm Disease - Frequently Asked Questions

About this FAQ

This page contains a selection of frequently asked questions (FAQs) about Dutch elm disease in Manitoba.

 

Contents:

 

Elm Tree Identification

Q. What does an elm tree look like?
A.
Elms are vase or umbrella shaped with rising branches from a single trunk. They have dark green, veined leaves that are toothed and uneven at the base. The bark is dark grey/brown and furrowed, with broad intersecting ridges and has a rough flaky appearance. In cross-section, the bark has alternating brown and white layers.


American Elm


American elm leaves and seeds



Dutch Elm Disease

Q. What is Dutch elm disease?
A.
Dutch elm disease is a fungal disease that blocks water movement in infected elm trees leading to the death of the tree.

Q. Which trees get Dutch elm disease?
A.
The American elm is most susceptible to Dutch elm disease. The introduced Siberian elm (sometimes incorrectly referred to as Chinese elm) is resistant to Dutch elm disease but sometimes becomes infected.

Q. How can I tell if my elm has Dutch elm disease?
A.
Infected trees may produce small sparse leaves in spring if infected late in the previous growing season. If infected during the same growing season, you may notice a sudden wilting of leaves, usually at the top of the tree, in early to mid-summer. Leaves curl and turn brown but may not fall from the tree. If infected in mid to late summer, leaves may become yellow and fall prematurely. Symptoms can spread quickly throughout the tree. Infected branches often show a brown stain on the wood that can be seen by peeling back the bark. Note: If testing your own tree, sterilize your cutting tool after each cut to prevent spreading the Dutch elm disease fungus to other trees.


Tree infected with Dutch elm disease


Stain caused by Dutch elm disease

Q. How long does it take for Dutch elm disease to kill elm trees?
A.
Young, vigorously growing trees can be killed in a few weeks, whereas larger, slower growing trees can take one to two years.

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How the Disease Spreads

Q. How is Dutch elm disease spread from infected elms to healthy elms?
A.
In Manitoba, Dutch elm disease is most commonly spread by Native elm bark beetles. They breed in dead and dying elm material. Beetles emerging from brood trees that were infected with Dutch elm disease can be contaminated with the spores of the Dutch elm disease fungus. When these beetles move to other elms to feed or over-winter under the bark at the base of an elm, they can infect healthy elms. Dutch elm disease may also be spread from tree to tree if the roots of an infected tree are touching the roots of a healthy tree.

Q. What does the native elm bark beetle look like?
A.
The adult beetles are tiny (2-3mm) and dark brown and are difficult to see.

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Prevention and Control of Dutch elm disease

Q. What can I do to prevent Dutch elm disease from infecting my healthy elm?

A.
  • Do not store elm firewood. Elm wood can be disposed of by burning or chipping. You can usually dispose of elm material at your local landfill, please contact your municipality regarding the disposal of wood waste.
  • Have an arborist and/or a professional with a pesticide applicators license spray the base of healthy elms with an insecticide that is registered for use to kill elm bark beetles. The elm bark beetles spend the winter under the bark at the base of elm trees. Applications are done every two years in August or early September before the beetles move to the base of trees.
  • Keep elms in healthy condition through proper tree care (pruning, regular watering, and fertilization).
  • Have your healthy elm trees injected with a registered fungicide. This must be done by a trained arborist with a valid pesticide applicator license. Such treatments are normally reserved for high value elms, as the treatments can be expensive and have to be repeated every two years.


Elm tree being injected with a fungicide

Q. How should I dispose of elm wood?
A.
Dead or dying elm trees can be removed entirely any time of the year. Elms should be cut flush with the ground or debarked to the soil line, and either burned or chipped. Contact your municipal office for on-site burning regulations and for the location of the nearest disposal site.

Q. Can I keep elm as firewood?
A. No. Storing elm wood, a major factor in spreading Dutch elm disease, is illegal.

Q. What are those "sticky bands" I see wrapped around tree trunks? Do they control Dutch elm disease?
A. They are tanglefoot bands that prevent spring and fall cankerworm wingless female moths from crawling up the tree trunk to lay eggs. Heavy cankerworm feeding can cause severe defoliation that stresses and weakens trees. Reducing the stress on elm trees makes them less attractive to elm bark beetles. Tanglefoot bands may also play an incidental role in trapping a few bark beetles.

Q. My tree has sap leaking from the trunk and staining on the outer bark. Is this a sign of Dutch elm disease?
A. This condition, known as wetwood or slimeflux, is common in elm trees. It is not Dutch elm disease related. It is caused by bacteria and is more unsightly than harmful to the tree. Usually it occurs at a pruning wound or at the junction of two major limbs.


slime flux on elm tree

Q. Can Dutch elm disease be pruned from my elm tree?
A. No, Dutch elm disease cannot be pruned out of the tree.

Q. When can I prune my elm tree?
A. You can prune healthy elms to remove dead or damaged branches anytime except between April 1st and July 31st. During this time, beetles are active and would be attracted to open wounds making your tree more vulnerable to Dutch elm disease.
Note: It is important to sterilize your pruning tools between trees.

Q. Is there a cure for Dutch elm disease now?
A. No. Research is being done to find effective, cost-efficient treatments, and to develop Dutch elm disease resistant varieties of elm.

Q. Can you recommend a company to spray, prune, and/or inject my elms?
A. The Government of Manitoba cannot recommend a specific company, so please look in the phone book or search the internet under "Tree Service". Ensure that the company you select employs trained and qualified arborists and/or pesticide applicators.

Q. Is assistance available to remove dead/diseased elm trees?
A.A number of communities have agreements with the Government of Manitoba to manage Dutch elm disease. Under these agreements, the province assists participating communities by having trained inspectors survey the managed area for firewood and infected elms. Participating communities usually perform basal spraying of public elms and removal of elm trees identified and marked by provincial inspectors. For a list of managed communities, please go to http://www.gov.mb.ca/sd/forestry/ded-urban/ded_mgmt.html.

Q. I have a tree that is tagged for removal on my property. When will it be removed?
A. For further information, contact your local municipal or public works office.

Q. Who do I call if I suspect my elm tree has Dutch elm disease or for more information on Dutch elm disease?
A.
In the City of Winnipeg - Urban Forestry Department - 311
In Brandon - 204-726-6444
Outside Brandon and Winnipeg - 204-945-7866
Email - treecare@gov.mb.ca