Dutch Elm Disease

As the beetle bores into the bark of an elm tree, the beetle introduces the Dutch Elm Disease fungus into the tree’s vascular system, which carries water inside the tree. The fungus clogs these tubes, preventing 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 of 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 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 Arbotect 20-S. This is a new innovative approach we are using to control the disease in a 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 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 toward issues relating to our climate/zone.