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Dutch Elm Disease

What is Dutch Elm Disease (DED)?

Elm Canopy

Dutch Elm Disease (DED) is a wilt disease of elm trees caused by a fungus. The DED fungus was introduced into North America in the early 1900’s via infected elm wood transported from overseas. The disease was first detected in Manitoba right here in Winnipeg in 1975. The fungal infection results in the blockage of the tree’s water-conducting tissue and ultimately kills susceptible elm trees. The American elm is highly susceptible to developing DED when it is infected with the fungus.

In Manitoba, the fungus is spread between elm trees mainly by the native elm bark beetle as it feeds in the crown of elm trees. A young adult elm bark beetle carries the spores of the fungus on its body when it emerges from a diseased elm in late summer. The spores remain viable on the beetle’s body throughout its overwintering in healthy elm trees. When the beetle emerges in spring, it inadvertently transfers the fungal spores from its body into the wood as it feeds on the branches in spring and summer. The fungus also can be transmitted through the roots of adjacent elm trees whose roots have grafted together.

Symptoms of DED can be seen in early summer and initially as wilting and curling of the leaves. The leaves then turn yellow and eventually brown as the leaves die. The dead, curled leaves tend to persist on the tree. A sign of DED is dark brown streaking in the outer sapwood which can be seen by peeling away the bark on a small branch. The disease can kill an American elm within weeks of infection.

Dutch Elm Disease Control

The City of Winnipeg, Dutch Elm Disease (D.E.D.) Control Program attempts to ensure the well being, longevity and enhancement of the urban elm forest within the City of Winnipeg through the delivery of effective disease control and tree maintenance services on both public and private lands.

In the delivery of this public service, the program is committed to adopt, develop or maintain and/or improve existing strategies to:

  • Identify all elm trees and stored elm wood locations that require further attention.
  • Maintain a current tree inventory.
  • Remove all problem trees within accepted service standards.
  • Implement ongoing preventative procedures in elm tree maintenance and insect vector control.
  • Provide proactive tree replacement programs.
  • Research/develop new and existing strategies through various research institutions.
  • Provide information service through multimedia and on an individual basis.
  • Maintain/develop partnerships to enhance D.E.D. programs/procedures.

In addition to the above general program services, City of Winnipeg residents can request specific and detailed Dutch Elm Disease information from 311

Frequently asked questions

Can I store Elm wood for firewood?

The Forest Health Protection Act and Regulations prohibit the storage of elm wood for any purpose unless the wood has been treated as described below:

  1. all bark has been removed from the wood;
  2. the wood has been treated by
    1. kiln drying it to a moisture content of 18% or less, or
    2. heating it to 56°C for at least 30 minutes;
  3. the wood is chipped to have thickness of wood adhering to the bark in any dimension of not more than 5 cm; or
  4. a storage permit is obtained from the director.

The restriction on the storage of elm wood is necessary as the elm bark beetle uses intact wood as a site to lay eggs and develop a new generation of elm bark beetles. This brood wood results in an increase in the population of elm bark beetles, and more importantly, if the wood is infected with the DED fungus, the new generation of elm bark beetles carries that fungus on its body when it emerges from the brood wood in late summer and overwinters, and then transfer the DED fungus to healthy trees in the spring when it feeds in the canopy of elms - hence spreading the disease.

The Urban Forestry Branch recommends the best ways to dispose of elm wood are by:

  1. taking the wood to Brady Road Resource Management Facility,
  2. chipping the wood to pieces as indicated above (the wood chips can be used as mulch), or
  3. burning the wood on site upon obtaining an Open Air Fire Permit from the Winnipeg Fire Paramedic Service located at 2nd Floor, 185 King Street.

If you have received a notice to dispose of the elm firewood in your yard and you are not sure which is elm—the elm logs are marked with red lumber crayon.

Once you have disposed of the wood, please notify the Urban Forestry Branch as indicated on the notice so we can confirm that you are in compliance with the notice.

Please note at no time is it legal to transport elm wood for any other reason than disposal at a landfill designated to receive elm wood (Brady Road Resource Management Facility), AND at no time is it legal to store elm wood with intact bark, or that does not meet the criteria listed above as per the Forest Health Protection Act and Regulations, for burning or any other use.

How do I recognize if my tree is infected?

Look into the tree canopy, wilting of leaves is usually the first stage of DED, followed by yellowing then browning of the leaves. If you are unsure please call 311 for a Forestry Technician to inspect.

What should I do if the tree looks unhealthy?

The Urban Forestry Branch inspects all elm trees in Winnipeg for Dutch elm disease annually from mid-June to mid-September. If your elm tree looks unhealthy and you are not sure if it has DED, please call 311—they will send a Service Request to the Urban Forestry Branch for a Technician to inspect the tree.

Can I remove the infected elm tree on my property?

Yes, complete removal to ground level can be done at any time. The stump should be debarked and all the wood disposed of at the Brady Road Resource Management Facility. Removals on private property done by the Urban Forestry Branch will occur at no charge to homeowner. These trees will be marked with orange flagging tape or paint.

When can I prune an Elm?

No person shall prune Elms during the period commencing April 1 and ending July 31.

Does the city have a DED Inspection Program?

Yes, inspections are done between mid-June and mid-September. The program also accepts and actions reports of illegal elm pruning and stored elm firewood.

What steps are taken once I ask for my tree to be inspected for DED?
  1. Tree will be inspected within the month
  2. If the tree is marked for removal (and on private property) the homeowner will receive notification in their mailbox.
  3. This notice will have an Urban Forestry contact number if they have further questions.
  4. The tree will be removed within 1 year. Note that the homeowner will be responsible for removing the stump.
  5. If the tree is not marked for removal (i.e. not DED) the homeowner will receive information on the diagnosis of the tree.

These services can be accessed through the City of Winnipeg, call 311.

What are elm tree injections?

There is a variety of products registered for use in Canada as injection applications in the management of Dutch elm disease (DED). The City of Winnipeg currently does not use these treatments in its DED management program. As the City manages DED on a large scale, timely sanitation and elm bark beetle control are the strongest components in reducing the spread of the disease and preserving our elm canopy.

Some homeowners may choose to have trees of high value treated to preserve them. The treatments are most effective when applied to healthy trees and must be repeated annually every few years, depending on the product. Injection treatments are not intended to replace sanitation practices.

Some tree care companies offer these services in Winnipeg and these companies can be found in the yellow pages under "Tree Services". These treatments should be done by a professional arborist to ensure proper application. The arborist should also hold a valid Manitoba Pesticide Applicator License.

If homeowners wish to have elms on public or city-owned property treated at their own expense, they must hire contractor services via the property owner's agreement. See Guidelines for maintaining City-owned trees using a qualified contractor

Dutch Elm Disease Research

Pilot project to identify brood trees for prioritized rapid removal for DED management

The City of Winnipeg's Urban Forestry Branch is collaborating with The University of Winnipeg's Centre for Forest Interdisciplinary Research on a Dutch elm disease (DED) research project to identify and prioritize the early removal of brood trees. These brood trees represent the small percentage of diseased elm trees that host the majority of elm bark beetle brood. The goal is to develop a simple, cost efficient and quick sampling technique to help prioritize trees for rapid removal. The pilot project will also assess the effectiveness of this approach.

Previous research conducted at the University of Manitoba revealed new information about the activities and life cycle of the native elm bark beetle in Manitoba. In summer, the female elm bark beetle uses diseased and unhealthy elms to produce a new generation of beetles, or brood, that emerge from these trees in late summer. These beetles carry the disease-causing fungus on their bodies. In fall, they burrow into the lower trunks and root flares of healthy elm trees to overwinter under the bark. When the beetles emerge from the trees the following spring, they still have the fungus on their bodies. As they feed in the canopies of healthy elms in spring and early summer, they transfer the fungal spores to the exposed tissue in the branches.

This research also found a small percentage of diseased elm trees contained very large amounts of elm bark beetle brood. One tree was found to have over 40,000 elm bark beetles. The findings from this research lead to a five-year rapid removal study conducted by the Province of Manitoba and the University of Manitoba.

The goal of the rapid removal study was to determine if early removal of diseased elms reduced the incidence of DED in Manitoba communities participating in the study. Traditionally, most diseased elm trees are removed during the fall and winter which gives the elm bark beetle the opportunity to breed in these trees in summer. In the five-year study, earlier removal of diseased elm trees by middle of August (rapid removal) was applied to half of the communities and winter removals were applied to the other half of the communities. This study revealed that with five years of a rapid removal regimen, the incidence of DED was cut by half as the beetle populations were reduced significantly over that time.

The City of Winnipeg piloted a rapid removal regimen in one neighbourhood in 2010 and throughout the City in 2013 to determine the feasibility and effectiveness of such a regimen. Although the targeted number of rapid removals were successfully completed in these pilots, the project identified logistical limitations in the rapid removal of thousands of diseased trees within a short timeframe.

In 2014, the University of Manitoba and The Province of Manitoba initiated a follow up study to determine a methodology to identify elms that attract such high numbers of beetles for brood development, or brood trees, in order to target these trees for rapid removal. The hypothesis is the spread of DED would be reduced by targeting the early removal of the small percentage of diseased elm trees that host the majority of the beetle brood, allowing more effective management of DED.

The City of Winnipeg and The University of Winnipeg are continuing the research by piloting the project in the City of Winnipeg beginning in 2017.The goal of this current pilot project is to further develop the methodology to detect elm trees that contribute most to the spread of Dutch elm disease in Winnipeg neighbourhoods. The research component by the University of Winnipeg is in final completion stage and the Urban Forestry branch is piloting the new methodology in summer of 2020.

Urban Forestry Branch:
1539 Waverley Street, Winnipeg, Manitoba R3T 4V7
Telephone: 311 | Fax: 204.222.2839

Last update: May 15, 2020
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