Dutch elm disease (DED) is a deadly disease that can affect any elm tree. Alberta has been fortunate to remain DED free for many years. However, landowners are still encouraged to be on the lookout for signs of DED on their properties. The tips below are designed to help landowners detect, control and prevent any possible DED outbreaks on their property.
Landowners are encouraged to follow the Dutch Elm Disease prevention and control measures listed below. To report a DED suspect elm tree or for more information, call the Society to Prevent Dutch Elm Disease (STOPDED) hotline at 1.877.837.ELMS or check out the website at www.stopded.org.
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.
Elm Preventive Pruning and Removal
Pruning elms can only be carried out commencing October 1 to March 31 the same year. Elm trees can be removed any time of the year. (see 4. below)
Preventive pruning or tree removal 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. (See 4. and 5. Below) 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.
Before any DED suspect tree is removed, the presence of the Dutch elm disease fungus must be confirmed. All DED suspect elm trees must be sampled properly and the samples sent to a lab approved by the Alberta Agriculture and Forestry for confirmation testing. Suspect DED samples are tested at no cost to sender. Suspect DED sample instructions can be found on www.stopded.org and click on “Sampling Procedures”. Call the STOPDED hotline at 1-877-837-3567 for more instructions.
Elm Tree Removal
An elm tree can be removed at any time of the year as long as it is immediately disposed. (See 5. below) Elm tree removal means to remove the trunk and all other parts of a tree including the stump
When an elm tree has tested positive for DED, the tree must be removed immediately and properly disposed. (See 5. below.) The stump must also be properly treated. (See 7. below) 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 regardless of the reason for their poor condition.
Elm Wood Disposal
Elm wood cannot be stored, or transported unless in route to the closest elm wood disposal site. All elm wood must be properly disposed of immediately by either burning of or burying to a minimum depth of 25 cm. If elm wood is uninfected with DED, another option is chipping. (see 6. below) 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.
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 may be chipped into pieces not more than 5 cm. Larger elm wood chips can harbor the vector. Chips must be destroyed or stock pile for at least one year before using them in a landscape setting. Elm wood chips give off an odor that will attract the vector, therefore must only be used on trails, shrub beds and as animal bedding in areas where elm trees are not growing nearby.
Elm Stump Treatment
All elm stump 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.
Hazard elm 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 hazard such as environmental causes or improper pruning such as topping. If an inspector has declared an elm tree to be a hazard, the tree must be removed and properly disposed of. (see 4. and 5. above)
Dangerous Branch or Whole Tree
Dangerous is defined as a branch or a whole tree that could negatively affect human safety or cause property damage. In the event an elm branch is damaged making it dangerous during the elm pruning ban, corrective pruning can only be done to the dangerous branch with inspector approval. A dangerous tree can be removed at any time of the year without inspector approval. (see 4. above) A dangerous tree is only a concern to DED prevention/control if it becomes a hazard. (8. above) All elm material must be properly disposed of. (see 5. above)