Ash borer battle in full swing

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This article was published 02/07/2018 (1725 days ago), so information in it may no longer be current.

The tree canopy is waning on Wavell Avenue, so it’s no surprise the sun is sizzling there a bit more these days.

The Riverview neighbourhood is one of many in Winnipeg whose boulevard ash trees have been affected by invasive insects, which were detected in the city last fall.

The emerald ash borer kills trees by feasting on the tissue below the bark, while the cottony ash psyllid, also called jumping tree lice, sucks sap from the leaves and causes severe leaf curling and defoliation.

Homes on the 200 block are especially exposed as a number of trees have few or no leaves, three trees have been cut down and two more trees will soon be removed.

“It’s so hot. You really miss the shade on days like this. It’s sad,” said homeowner Ina Nicholson, a retired teacher who has lived on the street for 20 years. “This is the third year they’ve looked bad.”

Ginny, who did not want her last name published, said she’s “sad to see the trees dying.”

“It’s a real shame. It’s no one’s fault, but I wish they (the city) could have gotten on this a bit sooner,” said Ginny, who has lived on the street for 33 years. “They just look so sick and they’re losing their leaves.”

City forester Martha Barwinsky said the city’s ash tree population — about 101,000 on boulevards and in parks and about 256,000 on private property and natural areas — is in danger of being wiped out, but the fight against the ash borer is in full swing.

She said about 1,000 green ash trees were selected for treatment under strict criteria. Insect control crews are injecting tree trunks with one of two products, TreeAzin and an imidacloprid chemical. Barwinsky is studying how each works logistically and operationally.

“We’re new at this, so we want to try both products out,” Barwinsky said. “We’re treating trees in similar locations so we can compare them more closely.”

The treatment costs $200 per tree. The city has earmarked $1.3 million this year for the battle, and anticipates it will spend about $90 million over the next 10 years.

Barwinsky said an additional 80 trees will be treated thanks to a donation of 12 litres of TreeAzin to the city by Tree Canada.

Green ash trees were chosen for treatment because they’re generally healthier right now and not a main target of the two pests.

Barwinsky said black ash, Mancana ash and their hybrids are most susceptible to the borer, and are already being attacked by the cottony ash psyllid.

She said it’s too early to tell how the fight is going.

“Once (the ash borer) rips through our canopy and those trees are still standing, then it’s considered that the treatment’s been effective,” she said. “It could take 10 years or 15 years, or it could take 20.”

She said the city has partnered with the University of Winnipeg in a research project to analyze samples from the original trees in St. Boniface which were identified as having emerald ash borer to determine exactly when the trees were infected to get a definitive answer on how long the ash borer has been in Winnipeg.

The city has also formed a partnership with the Canadian Forest Service to examine the cold tolerance of the borer to find out how rapidly the population will spread based on its survival after Manitoba winters.

She said some research shows its life cycle is two years in colder climates as opposed to one year in warmer locations. She said the hope is that winter will be hard on the beetles.

“We have to find some hope in this somewhere,” she said, noting a two-year life cycle (egg to beetle) gives the city more time to battle the bug and study it.

She said 13 trees that were tested positive for the beetle were removed from St. Boniface last year, and another 800 ash trees will be removed this year as a proactive measure to get rid of trees which are susceptible to the insect and won’t be treated.

“In the peak of (beetle) population, we could end up with thousands of trees that have to be removed in one year. Once an ash tree dies from emerald ash borer, within two years it starts falling down, so it becomes a very serious public safety risk,” she said. “With proactive removal and strategic injections, we may be able to strategically slow down the spread of the beetle.”

In Manitoba, there are no natural predators for the beetle.

Barwinsky said the city has been in communication with the Canadian Forest Service about releasing biological control measures, such as parasitic wasps being used in Ontario, but those are simply additional management tools. There is no way to eradicate the insect population. No other city or area has been able to kill it, Barwinsky said.

“We’ve installed 200 traps around the city to enhance our monitoring program,” she said. “If the beetle does have a two-year life cycle, that’s actually a good thing. We’ll have more time to manage the mortality of our ash trees and spread those costs out over time and be able to replace those trees.”

Barwinsky said replacement trees will include a wide variety of species.

“The way I look at it, if there’s a positive thing to come out of this, it’s the reinforcement of how diversity is so important in our urban forest,” she said.

ashley.prest@freepress.mb.ca