Dutch Elm Disease
Dutch elm disease (DED) is an incurable and deadly fungal disease of elm trees. The fungal spores enter the tree, clogging the vessels that transport water and nutrients up and down the tree. This usually kills the tree in 3 - 5 years.
Click here for detailed facts about Dutch Elm Disease.
Click here to view pictorial information about DED
How is DED spread?
Dutch elm disease can spread by elm bark beetles or through root grafts and human activity.
Larval feeding under tree bark causes fern-like wounds unique to elm bark beetles.
DED in Charlottetown
- Elm bark beetles are small, shiny brownish-red beetles that are rarely visible to humans. Their activities, (egg laying, larvae feeding and overwintering), cause wounds in the elm trees. These wounds and the elm bark beetles themselves, release chemicals that attract more beetles to the elm trees. Elm trees can also have other wounds, such as pruning cuts or storm damage, which causes the tree to release a chemical that attracts the beetles. The beetles become covered with fungal spores from infected elm trees, which they spread to healthy trees as they move from tree to tree.
- There are a number of human activities that can spread Dutch elm disease such as: moving or storing infected elm wood; pruning infected/healthy elms without cleaning pruning tools between cuts; pruning elms when elm bark beetles are active (beetles hibernate during the winter); not removing DED infected elms; and improper disposal of DED infected wood (such as firewood).
- Tree roots from adjacent trees can connect and form grafts that allow nutrients and water to move back and forth from tree to tree. Fungal spores can be passed from tree to tree as well.
Drooping, wilting, curling, yellowing or browning of the leaves at the ends of the branches (called flagging) is one symptom of DED. Photo by Andrew Williams.
DED was first recorded on PEI in the late 1970's. Charlottetown has been dealing with DED since 1996 through its tree maintenance program.
Charlottetown is not unique in its dealings with Dutch elm disease. Many municipalities across Canada from Manitoba to the Maritimes, have been struggling to manage this disease with varying degrees of success.
All of the native elms are susceptible to Dutch elm disease and, once they are infected, there is no known cure.
The Province conducted a partial survey of elm trees in the summer of 2014. The City followed up with a full survey of elms on municipal land with the following results:
|Total number of Elms on City right-of-way
|Elms Infected with DED
More than half of the City's elm trees are infected with DED. These trees cannot be saved and will die within a few years. Many of these elms are located along streets, sidewalks and in our parks where there is high pedestrian or vehicle traffic. They are also located close to residential housing and businesses. The dead elms start to decay, exhibit poor structure and can become a hazard in the urban landscape.
DED, if not controlled, can quickly spread to our remaining healthy elm trees creating hazards and resulting in the loss of some of the City's largest and most beautiful trees.
The City of Charlottetown conducted a second inventory of diseased, dead, and healthy elms in 2014 to include private land in Charlottetown. Below is a table displaying the results of the most recent survey:
Dutch Elm Disease Management
This photo depicts a healthy elm tree.
Positive steps have been taken to replace some of the elms the City has lost to Dutch elm disease. The City has planted DED resistant elm cultivars. Also, a variety of other trees species have been planted throughout the City right-of-ways and parks, which increases the biodiversity of our trees and makes the urban forest less susceptible to insects pests and diseases. Since 2010, about 70 healthy elms have been inoculated annually in an attempt to increase their resistance to DED.
As in some other municipalities, Charlottetown is seeing a significant increase in the number of DED infected trees due to stress from:
- Weather events, such as drought and severe storms.
- Milder winters that result in low bark beetle mortality.
- The presence of a greater number of DED infected elms in the City.
- Use of elm wood for firewood, etc.
Unfortunately, past efforts have not stopped the spread of the disease. By applying proper management practices, it is possible to save some of the remaining elms. These elms provide numerous economic, social and environmental benefits to the city and its people.
Click here for more information on the benefits of the tree canopy in Charlottetown
After consulting other municipalities, and doing extensive research, the City of Charlottetown has been developing publications and gathering information that will further the management of DED.
Key components of a successful DED management program include monitoring, sanitation, tree planting, communication, education and community engagement.
Click here for Elm Tree removal numbers in some of the other municipalities dealing with DED
What Does This Mean For Privately Owned Elm Trees?
To implement a disease management program for DED, it is important that privately owned elm trees are monitored and diseased trees removed. If infected trees (public or private) are left in the urban forest, they will continue to spread DED, making attempts to save the healthy elm trees futile.
The City is taking responsibility of all elm management on both public and private land. Here's what you need to know if you have elm trees on your property:
What Does This Mean For Elm Trees on Public Property?
- 196 elm trees on private property have been identified as dead or diseased;
- All DED infected and dead elm trees will be removed, including those on private property. This work will be paid for by the City;
- You will be contacted by the City of Charlottetown if you have any elm trees on your property that are dead or diseased;
- Monitoring programs are being implemented to identify DED symptoms and watch healthy elm trees that may be at risk of being infected;
- Elm wood must be disposed of properly (burned or buried);
- You will be informed in advance if a dead or diseased elm tree must be removed from your property.
- Stump grinding will be completed for every elm removed. Any property damage will be reinstated.
- A public session was held on February 23, 2015 to provide an opportunity for the public to ask questions and get more information.
The City is taking responsibility of all elm management on both public and private land. Here's what you need to know about elm trees on public property:
Reducing the Spread of DED
- 127 elm trees on public property are diseased or dead;
- All DED infected and dead elm trees will be removed (public and private property);
- The City of Charlottetown will do its best to notify the owners of property in close proximity to a publicly owned elm tree that is being removed;
- Monitoring programs are being implemented to identify DED symptoms and watch healthy elms that may be at risk of being infected;
- Stump grinding will be completed for every elm removed. Any property damage will be reinstated.
- The City will plant two trees on public property for every one elm tree that is removed from public property;
- There are some diseased elms in our City squares that will have to be removed. Fortunately, there are many other species of trees in our squares that will remain;
- A public session was held on February 23, 2015 to provide an opportunity for the public to ask questions and get more information
Keeping your elms healthy by providing water and fertilizer when needed and carrying out proper pruning makes your tree less stressed and more resistant to insect and disease pests.
- If you have a healthy elm tree that you would like to protect, you can hire an arborist to inoculate your tree to increase its resistance to DED.
- Regular monitoring of your elm trees helps to detect DED symptoms when they first appear.
- Pruning may extend the life of your elm tree but will not save it once it is infected…. there is no known cure for DED. To prevent the spread of DED, the best management strategy is to remove the infected tree.
- Elm species should NOT be pruned between April 1 and September 30 as these open wounds attract the elm bark beetles which spread DED.
- Timely removal and disposal of infected trees: Once DED is detected in a tree, the tree should be removed that fall/winter season, after the elm bark beetles are hibernating (after September 30). When an elm is removed, the stump should be ground.
- Proper disposal is important. All elm wood should be disposed of by March 31. Any elms that must be removed during the summer months (i.e. for safety reasons) must be immediately burned or buried. When transporting the wood at this time of year, it should be taken directly from the location of removal to the point of disposal.
- When planting trees, choose other resistant species or plant DED resistant cultivars of elm such as: Patriot, Pioneer, Regal, Valley Forage, Princeton, New Horizon, etc.
One of the most important ways to prevent the spread of DED is to not store elm wood as firewood. Elm firewood provides a great habitat for the elm bark beetles to carry out their lifecycle. The more successful they are at reproducing, the more beetles are present, the more DED is spread to healthy elm trees.
As the City moves forward with the DED infected elm removal program, there will be piles of elm wood in our Squares and along our streets that will be picked up by City staff. The City will not be releasing any of this elm wood to individual homeowners. Your co-operation will help reduce the amount of DED that is present in our urban forest.
Still have questions? Contact us at: 902-566-5548