Dutch Elm Disease
Dutch elm disease is caused by a fungus that attaches itself to elm bark beetles. As the beetle bores into the bark of an elm tree, the beetle introduces the fungus into the tree’s vascular system which carries water inside the tree. The fungus clogs these tubes and prevents the tree from transporting the necessary nutrients and water to its canopy leaves. Eventually, the tree dies because it is starved for moisture. The disease can also be spread by contaminated pruning equipment. There is no cure and infected trees must be cut down to prevent further spread.
Symptoms of Dutch elm disease include:
- The first sign is wilting leaves, a result of blocked water-carrying tubes
- Leaves may turn yellow if trees are infected in the spring or early summer
- Leaves may turn brown and not fall off if trees are infected later in summer
Dutch Elm Disease Control Program
The City of Regina implemented a Dutch Elm Disease control program to reduce the spread of Dutch elm disease and limit the number of local trees lost.
Step 1 – Monitoring and Surveillance
City workers systematically inspect all City-owned and private trees once every two weeks for wilting or yellow leaves on one or more branches on a tree.
If a tree looks suspect, staff take samples and submit them for laboratory culturing to see if the tree has the DED fungus.
Step 2 - Elm Bark Beetle Monitoring
Elm Bark Beetles can carry the Dutch elm disease fungus as they move from tree to tree, so we monitor beetle numbers throughout the city.
To accomplish this we use pheromone traps. We have 86 traps set up to attract and capture three species of elm bark beetles (European, native and banded).
The US Forest Service provides great photos and explanations of Elm Bark Beetles.
Step 3 - Pruning and Sanitation
The City immediately cuts down and buries all infected wood from elm trees at the landfill. We also prune deadwood from City elm trees and remove hazardous trees after the pruning ban is lifted on August 31 each year.
Dutch elm disease can spread easily because trees are often planted close together. Under the ground and through tree roots is one way the disease begins to spread. The roots of trees closely planted together begin to graft and act as one giant root system. To stop the fungus from spreading underground, we inject neighbouring trees with a fungicide called Eertavas. This is a new innovative approach we are using to control the disease in more environmentally friendly way.
In the past, we would spray the bottom of elm trees with chlorpyrifos, an insecticide to control the beetles as carriers of the disease. Now we focus more directly on the disease itself by targeting the fungus on the inside of the tree and its root system, not on the carrier insect.
Step 4 - Infill Planting
Each spring and fall, City crews plant tree species in locations where elm trees have been removed due to age, damage, or disease. This includes new elm trees as well as a variety of other species so we can increase the biodiversity of our urban forest.
Step 5 - Firewood Inspections and Collections
Elm firewood is ideal for elm bark beetles to lay eggs. Provincial regulations state you cannot store, use, market or transport any elm tree for any purpose. If the City finds elm wood on your property, workers will leave a letter advising you to dispose of the firewood. If you don’t remove the firewood, the City will collect it and destroy it. The City’s Pest Control Team will help you to identify elm firewood or investigate reports of suspected elm firewood on private property.
Step 6 - Public Awareness
The City educates residents about Dutch elm disease through media interviews, radio, television and print advertising as well as brochures, fridge magnets, and tree ribbons. The City also placed signage at all City entrances advising motorists to the danger of transporting elm firewood.
Step 7 - Research
Research allows Pest Control to keep in touch with the latest developments and assists in directing efforts towards issues relating to our climate/zone. The fungicide Eertavas was a result of one of such research trials. When the product was in its field trial stage, the City participated in those trials. Now we’ve incorporated those results into a long-term program going forward.
What can residents do?
- Do not bring firewood from campsites or cabins into Regina where beetles may reside.
- Do not prune between April 1 and August 31 each year. Provincial legislation prohibits pruning during this period because the sap scent from a fresh cut attracts the elm bark beetle.
- When pruning is allowed, remove dead or broken branches from your private elm trees. Sterilize your pruning equipment with methanol (gasoline antifreeze) between cuts.
- Hire a licensed applicator apply a basal spray to your private elm tree in the fall.
For more information, review our Dutch Elm Disease brochure. Use the City's online Contact Us form or call 306-777-7000 if you suspect a private or City-owned tree in your neighbourhood has Dutch elm disease.