A new field guide and e-learning course are providing Albertans with the tools to identify their trees, recognize common pests, and protect the trees that make our communities greener.

Alberta’s urban and rural trees face growing threats from invasive pests that can cause devastating and lasting damage. For example, Dutch elm disease (DED) is an invasive tree disease not yet fully established in Alberta. While there have been several detections in Edmonton since 2024, rapid response has kept DED from establishing and spreading in the province. DED has had deadly effects on urban elm trees in eastern and central Canada. Nearly 90% of Montreal's elm trees and 80% of Toronto’s elm trees were lost due to DED during the 1970s, and populations have never fully recovered. Financial losses from DED exceed $2.5 billion in Canada and would be detrimental to the large populations of elm trees found in Alberta’s urban centres if it establishes.

Emerald ash borer (EAB) presents another threat. EAB is an invasive insect that causes deadly destruction to ash trees. Edmonton and Calgary alone have over 250,000 urban ash trees, which would be at risk if emerald ash borer were to establish in Alberta. Once EAB establishes, it can take hold quickly and be very difficult to eradicate, making early detection imperative to protect these trees.

What is an invasive species?

Invasive pests present an urgent concern. When introduced outside their natural range, some species can cause significant environmental, economic, and social harm. Often, invasive species are specialized to take advantage of their new environments. They may have aggressive life strategies that allow them to reproduce quickly and are well-adapted to out-compete the native species for food, space, and other resources. These species often lack any predators or natural methods of control, so populations are able to grow rapidly. Not all introduced species are considered invasive, but once an invasive species is established, controlling it requires significant time, effort, money, and resources. It is estimated that invasive species cost Alberta over $2.1 billion a year.

The value of Alberta’s trees

Trees lining our streets, growing in our city parks, and planted on rural properties, provide countless benefits to Albertans. Trees reduce energy costs by providing shade and protecting houses and roads from wind, rain, and snow. They increase curb appeal and property value by bringing natural beauty to neighbourhoods. Rural shelterbelts shield buildings from weather, support agricultural operations, and can increase biodiversity. These trees improve community livability and have positive impacts on mental health and quality of life.

Like all living things, trees can be affected by pests and other sources of stress. Insects, mites, fungi, diseases, wildlife and weather can damage leaves, branches, bark, trunks, and roots, sometimes reducing the health and longevity of a tree. Alberta is home to many native insects and

diseases that interact naturally with our trees. Most are simply part of a healthy ecosystem, but some can cause significant damage when populations increase, conditions favour their development, or trees are already under stress.

How do we protect our trees?

Protecting Alberta’s trees starts with getting to know the trees growing around us and recognizing what may threaten them. Basic tree identification can help us understand which pests and diseases may affect a tree and whether signs or symptoms we see are cause for concern. Unusual leaf discolouration, premature leaf loss, holes in bark, thinning crowns, unusual growths, or insect and wildlife activity can all provide clues about a tree’s health. Not every unusual sign indicates a serious problem, but understanding what to look for can make it easier to recognize potential concerns early. Knowing what to look for and when to report a suspected invasive threat will prevent invasive pests from establishing.

Understanding how tree pests spread is also an important part of protecting our trees. While some pests disperse naturally, people can unintentionally move insects and diseases much farther and faster than they could travel on their own. Firewood, logs, branches, soil, and other plant material can provide pathways for pests to establish in new areas. Following recommended practices and regulations when moving these materials can help prevent the introduction and spread of invasive species. Don’t move firewood more than 80 km.

Tree care is another important piece of the puzzle. Healthy, properly maintained trees are often better able to tolerate environmental stress and recover from some types of pest damage. Watering and pruning trees properly, choosing appropriate trees for a site, and regularly checking for signs of declining health can all contribute to their long-term well-being. By combining good tree care with pest awareness and responsible practices, Albertans can protect our urban and rural forests.

Introducing new resources

To help Albertans build this knowledge, Alberta Invasive Species Council is launching two new resources: the Tree Pests of Alberta field guide and an accompanying e-learning course. Whether you’re a tree expert or are still trying to figure out what’s growing in your backyard, these resources will help you get to know your trees—and what might be bugging them! The new resources will include:

• Tips on how to keep your trees healthy and less susceptible to damage from invasive species throughout the year.
• Important information on preventing the introduction and spread of invasive tree pests.
• A contact list so you know who to report suspicious sightings to.
• Descriptions of Alberta’s 22 most common trees so anyone can identify their tree.
• Over 65 pest profiles featuring native and invasive insects, fungi, and diseases that may threaten your tree, including descriptions, signs and symptoms, and management options.
• An interactive and user-led online course that compliments the guide.

These practical resources are designed to help Albertans better care for and understand their trees, so we can keep Alberta’s trees happy and healthy for many years to come.

This project was made possible through support from the Alberta Real Estate Foundation. The Alberta Real Estate Foundation invests in projects that advance education, research, law reform, and other activities related to real estate that strengthen Alberta’s communities. The Foundation’s revenues come from the interest earned on consumer money deposited in real estate brokers’ pooled trust accounts.

Learn more at www.aref.ab.ca

About the Author:

Alberta Invasive Species Council is a non-profit organization dedicated to informing and educating Albertans about the destructive impacts invasive species have on our environment, economy, and society. We endeavor to foster partnerships with jurisdictions, agencies, and groups to develop integrated collaboration, long-term management programs, and to engage and empower people to take action against invasive species in Alberta.