Portage la Prairie's ash trees could be wiped out by a new threat damaging urban forests across North America.

Emerald Ash Borer (EAB) is an insect that has killed tens of millions of ash trees in the United States and eastern Canada. Portage la Prairie city council heard a presentation on the threat EAB poses to Manitoba communities from Kyla Maslanick, an urban forester from the forestry and peatlands management branch of Manitoba Sustainable Development, at its committee meeting Monday night at the William Glesby Centre.

“Emerald Ash Borer is a very serious invasive forest insect we don't yet have in Manitoba,” Maslanick explains. “But it's coming, and it's something (city council) needs to prepare for.”

According to Maslanick, communities as close as Duluth, Minn., to the south, and Thunder Bay, Ont., to the east are coping with EAB infestation. The pest can be hard to detect in the early stages of infestation. Maslanick says trees that are initially infected could survive up to five years. But as EAB spreads and multiplies, it could take out an ash tree within one or two years. EAB is spread primarily through the movement of infested firewood by people.

“That's the most important message we want to get out there: Don't move firewood,” says Maslanick.

Portage la Prairie has approximately 8,700 ash trees — a large portion of what makes up the urban forest in the community.

An infographic that displays the concentration of ash trees in Portage la Prairie, highlighted in green, presented at city council's meeting earlier this week. (Manitoba Sustainable Development image)

“If you were to lose all those trees, that would have a pretty devastating impact,” says Maslanick. “It can impact property values. And consider, too, we're dealing with Dutch Elm disease at the same time. Those two species are really the two main urban species in Portage, as well as other communities in Manitoba.”

Portage la Prairie Mayor Irvine Ferris says EAB is a potential problem that will affect our community, and the city is weary of it.

“A significant part of our urban forest, almost 9,000 trees are ash trees,” Mayor Ferris says. “A lot of them were planted a number of years ago to replace the trees we lost due to Dutch Elm.”

“At the time they were planted there were no known pests. It was a beautiful shade tree,” continues Ferris. “This will have a significant impact on our community.”

Portage la Prairie Mayor Irvine Ferris during city council's Feb. 27, 2017 meeting at the William Glesby Centre. (photo by Matt Hermiz)

Ferris says the city's operations department stopped planting ash trees about two or three years ago after learning about the EAB threat.

Treatment options do exist for ash trees that are effective in the early stages of infestation, but can be costly. Maslanick provided a rough estimate of between $200-$400 per tree, and advised that other municipalities have applied the treatment to trees with a diameter of at least 30cm. The treatment has to be applied every two years. Maslanick says there is mixed opinion as to how long the treatment for ash trees is necessary for: anywhere between 10 years to infinite.

Ferris adds: "It's been on the radar for a little while, but even more so we're going to be looking at: What are the treatment costs for saving the large trees? How fast does this spread? What are our options for removing diseased trees? And how do you budget for that? There are a number of challenges over the next few years.”