Winnipeggers unite to save their Elms from Dutch disease

Article: https://ici.radio-canada.ca/nouvelle/2150094/maladie-hollandaise-orme-winnipeg

Radio Interview: https://ici.radio-canada.ca/ohdio/premiere/emissions/le-6-a-9/segments/rattrapage/2030823/winnipegois-unis-pour-sauver-leurs-ormes-maladie-hollandaise

June 8, 2025

Residents of Newman Street, in Winnipeg's Wolseley neighbourhood, have rallied together to save the last seven elm trees on their street from Dutch elm disease. This scourge, which has affected the city for 50 years, remains a major challenge for the preservation of its urban forest.

For about ten years, the trees on Newman Street have been marked with a red circle and are gradually disappearing due to Dutch elm disease, says Michelle Wadelius, a longtime resident of the neighbourhood. Many old elm trees were cut down due to this disease, and it has really affected the canopy and shade in our community, she explains, adding that when she arrived in the neighbourhood, the street had about twenty elm trees.

In 2022, she and her husband managed to mobilize about fifty neighbors to collectively find and fund an injection treatment that would give elms 99% immunity against Dutch disease over a three-year cycle.

"We collectively spent about $4,000 to inject the seven elms in 2023, the cost varying depending on the diameter of each tree," says Ms. Wadelius.

Studies have shown that the absence of a canopy allows the sun to shine directly on houses, making them much hotter.

We had to install air conditioning for the first time because our house was starting to get warmer." Michelle Wadelius, a longtime resident of Newman Street in Winnipeg

A 50-Year-Old Scourge

Debuting in 1975 in Manitoba's capital, Dutch elm disease causes vascular wilt in the tree, explains Martha Barwinsky, City of Winnipeg forester.

The American elm is particularly susceptible to this disease, which is caused by a fungus that penetrates the tree, primarily through the elm bark beetle, a native insect that feeds on trees in early spring and summer. Martha Barwinsky, City of Winnipeg forester

She explains that this fungus, transmitted by the elm bark beetle, blocks the tree's water-conducting vessels, causing wilting symptoms such as yellowing leaves and brown streaks on the wood, eventually leading to the tree's death.

In addition to providing shade during hot weather, these trees serve as a habitat for many organisms, including microscopic ones, and play an essential role in carbon sequestration.

In Winnipeg, we live on the prairies. We certainly don't have the diversity of tree species found in other parts of the country. As a result, some neighborhoods, even blocks, risk being completely stripped of their canopy in a very short time if we don't continue to fight Dutch elm disease, warns Ms. Barwinsky.

Integrated Pest Management for Dutch Elm Disease

Managing Dutch elm disease is part of an integrated pest management program. This management strategy includes disease surveillance, control of bark beetles, which carry the disease, a ban on storing elm firewood, and public education. However, this strategy is not intended to control the spread of the disease.

Preventative injection treatments are generally more suitable for small tree populations or individual trees due to their high cost and limited application timeframe, explains Ms. Barwinsky.

However, the City has stopped controlling the elm bark beetle for over a year due to the unavailability of the pesticide. According to her, other factors contribute to its spread, particularly when the roots of several elm trees in close proximity join together. Despite these challenges, Barwinsky believes the program, which has a budget of $5.4 million in 2024, is still achieving positive results.

We were able to measure the benefits [...], which include pollution control, reduced emissions, and increased cooling benefits. There are also many other benefits that are very difficult to measure, such as improving our social, mental, and physical well-being, etc. Martha Barwinsky, City of Winnipeg Forester

In 2020, the City implemented a pilot project in collaboration with the University of Manitoba and the University of Winnipeg to understand why some elm trees harbor large numbers of bark beetles, which can reach up to 40,000 individuals in a tree.

By identifying these super-progenitor trees, we may only expect to have 200 trees removed this season [compared to 6,000 normally]. This way, we can significantly reduce disease pressure, explains Barwinsky.

In addition to this strategy, the City of Winnipeg plans to plant a variety of trees to limit the spread of the disease, while continuing its efforts as part of its control program.

For her part, Ms. Wadelius plans to re-treat the seven elm trees on her street to preserve them for three more years, if she doesn't receive assistance from the municipal, provincial, or federal governments.