Dutch Elm Disease – Prevention and control

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Alberta’s response plan

Together, government and Albertans play an important role in preventing Dutch elm disease (DED) from destroying our elm trees.

• Provincial government – the Alberta government supports this critical effort by providing annual financial support to STOPDED to administrate and operate the Provincial DED Prevention Program, and by administering the APA and the PNCA which provides a means to enforce DED prevention measures.
• Local governments – under the APA, all municipalities, counties and MDs in Alberta have the responsibility and authority to prevent and control DED. Municipalities are encouraged to implement a Alberta Dutch Elm Disease (DED) Response Plan. See also DED – Responsibilities and authority.
• Society to Prevent Dutch Elm Disease – STOPDED helps foster and promote the survival of American elms in Alberta by raising public awareness and administering the DED Provincial Prevention Program.

How you can help

Albertans can help prevent and control DED:

• Learn to identify an elm tree and recognize the signs and symptoms of DED.
• Follow best practices to keep your elm trees healthy and less susceptible to DED.
• Know the laws that help prevent DED, and take preventative measures.
• Report all suspect infected trees immediately to the STOPDED Hotline at 1-877-837-ELMS (3567).
• Support STOPDED by becoming a member.

Preventive/Control measures

Best practices

‘Elm tree’ means any tree or part of a tree of the Ulmus genus and its cultivars, including the American, Siberian and Japanese elm. Follow these best practices to help keep elm trees healthy and less susceptible to DED:

• Keep your elm trees healthy, vigorous and properly pruned.
• Water elms from April to mid-August. To allow the tree to harden off for the winter, stop watering in mid-August, followed by a good soaking or 2 before freeze-up.

Enforceable steps

Download a printable version of this information.

The following prevention/control measures are enforceable under the APA and must be followed:

1. Elm pruning ban

Pruning ban period means the period commencing on April 1 and ending on September 30 of the same year. Elm bark beetles (EBB), the vectors of DED, are active between these dates and can be attracted to the scent of fresh tree cuts, possibly infecting a healthy tree.

2. Elm preventative pruning

Pruning elms can only be carried out commencing October 1 to March 31 the following year. Elm trees can be removed any time of the year (4. Elm tree removal)

Preventive pruning is essential to eliminate breeding material for the elm bark beetles (EBB). Preventive pruning is the systematic removal of dead, damaged, or diseased (other than from DED) branches from healthy elm trees. If a tree is dead or dying it should be removed. All elm wood must be properly disposed (4. Elm tree removal; 5a. Elm wood disposal). Keeping elms well-maintained will aid in the control of DED.

Improper pruning techniques and tree topping can weaken the elm tree, creating a hazard and increase the risk of attracting EBBs.

To avoid spreading DED, all equipment must be sterilized before pruning a different elm tree. To sterilize your tools, use methyl hydrate, a 25% solution of bleach and water, or a 70% concentrate of rubbing alcohol. Note that bleach can rust iron- based tools.

3. DED confirmation

The presence of the DED must be confirmed by a laboratory test. If a tree is removed before diagnostic testing is complete, the tree must be treated as if it is infested with DED and disposed of according to the guidelines (5a. Elm wood disposal).

All DED suspect elm trees must be sampled properly and the samples sent to Alberta Agriculture and Forestry’s Alberta Plant Health Lab for diagnostic testing. Suspect DED samples are tested at no cost to the sender.

All samples taken from private trees must be sent to the lab by a Municipality, Ag Fieldman, Tree Company or STOPDED. Tree Companies must contact the municipality, Ag Fieldman or STOPDED before sending a sample to the lab. Samples cannot be sent directly by a property owner.

Once the sample is confirmed to be DED positive, the lab will contact the appropriate contacts for a regulated pest detection.

For information on submitting suspect DED samples and a submission, see DED – Submitting samples.

4. Elm tree removal

When an elm tree has tested positive for DED, the tree must be removed immediately and properly disposed of (5a. Elm wood disposal). The stump must also be properly treated (7. Elm stump treatment). Prompt removal of infected trees is an imperative first step in slowing down the spread of DED. To eliminate EBB breeding material, remove all dead and dying elm trees.

An elm tree can be removed at any time of the year as long as it is immediately disposed of (5a. Elm wood disposal). Elm tree removal means to remove the trunk and all other parts of a tree including the stump.

5a. Elm tree disposal

Elm wood cannot be stored (5b. Elm wood storage), or transported unless en route to the closest elm wood disposal site. All elm wood must be properly disposed of immediately by either burning or burying to a minimum depth of 25 cm. If elm wood is uninfected with DED, another option is chipping (6. Elm chipping). Immediate disposal of the elm wood ensures the destruction of overwintering beetle larval broods and adults and eliminates EEB breeding material.

Every municipality must designate a disposal site where elm wood may be burned or buried.

5b. Elm wood storage

Storage of elm wood is prohibited at any time of year unless the wood has been treated as described below (following the Manitoba Dutch Elm Disease Act):

1. all bark has been removed from the wood
2. the wood has been treated by kiln drying it to a moisture content of 18% or less, or heating it to 56℃ for at least 30 minutes

6.  Elm chipping

If an elm tree is diagnosed with DED, all wood must be burned or buried. It cannot be chipped.

Elm wood not infected with DED can be chipped into pieces not more than 5 cm. Larger elm wood chips can harbour the vector. Fresh chips will give of a scent that will attract the vectors therefore chips may be destroyed or stock piled for at least one year before using them in a landscape setting.

7. Elm stump treatment

All elm stumps must be properly destroyed. A freshly cut stump with the bark still intact, gives off the same scent of a dead or dying tree. The remaining stump from a DED infected tree can also produce infected shoots. Remove the stump to a minimum depth of 10 cm below the soil line and fill the hole with soil or treat the elm tree stump in a manner satisfactory to an inspector.

8. High-risk tree

A high-risk tree is defined as a stressed tree that has deteriorated to the point of making it capable of supporting elm bark beetle habitation and breeding. There are many reasons why a tree may become a high risk such as environmental causes or improper pruning such as topping. If an inspector has declared an elm tree to be a high risk, the tree must be removed and properly disposed of (4. Elm tree removal; 5a. Elm wood disposal).

9. Hazard tree

Hazard is defined as a branch or a whole tree that is in imminent danger of failing and causing damage or harm to property or people. In the event an elm branch is damaged making it a hazard during the elm pruning ban, corrective pruning can only be done to the hazard branch with inspector approval. A hazard tree can be removed at any time of the year without inspector approval (4. Elm tree removal). All elm material must be properly disposed of (5a. Elm wood disposal).

Resources

See all DED forms and documents.

Contact

To report suspect DED symptoms or for more information, call:

STOPDED Hotline: 1-877-837-ELMS (3567)

For compliance and enforcement issues, contact your local municipality or Agricultural Fieldman.