The City of Vancouver is injecting ash trees with a pesticide as it looks to deal with the invasive emerald ash borer beetle, a species responsible for millions of ash tree deaths across the continent.
The pest, native to northeastern Asia, including China, Korea, Japan, Mongolia, and parts of the Russian Far East, was first detected in Vancouver last year by the Canadian Food Inspection Agency (CFIA), prompting concerns for thousands of urban trees in the city.
It likely arrived in North America on wooden crates, pallets or dunnage from goods imported from East Asia in the early 1990s, according to Natural Resources Canada.
First detected near Detroit, Michigan, and Windsor, Ont., in 2002, the beetle has spread to more than 30 states and five provinces since then.
Last month, the CFIA said that it detected beetle infestations within the City of Surrey, and there are restrictions on moving ash tree products in certain Metro Vancouver communities as a result.
The City of Vancouver said that ash trees represent around five per cent of the city’s tree inventory, or around 8,600 trees in total, and losing them would result in a “significant canopy loss.”
A University of B.C. professor says there are tremendous negative consequences to losing ash trees to the beetle, and residents should report any ash trees that look diseased to the authorities.
“It removes the canopies when the trees are dead, and that tends to have bad consequences,” said Richard Hamelin, the chair in forest conservation at UBC.
“Cities heat up … without the shade, and the air quality is diminished. So there’s a lot of bad consequences of having trees die in our cities.”
Many of the trees in the Domaine Saint-Paul, a woodland on Montreal’s Nuns’ Island, are being slowly killed by the emerald ash borer beetle. The local borough is planning to remove a large swath of the doomed trees, although a citizens’ group is pleading with it to slow the process.
Hamelin said that female emerald ash borers lay their eggs in ash trees, and the larvae burrow inside the tree and make tunnels, which end up cutting off the tree’s water supply, killing the tree within two to five years.
“This beetle has done a lot of damage in eastern Canada and eastern North America where there’s large populations of native ash trees,” he said.
“In British Columbia, we have only one native ash tree, and it’s the Oregon ash tree … and that’s present in the southern part of the province, in the lower Fraser Valley,” he added. “So, that is concerning, of course.”
No mass die-off, city says
The CFIA has instituted containment zones in Metro Vancouver to deal with the emerald ash borer infestation, specifically in the University of B.C. Endowment Lands, Vancouver, Burnaby, New Westminster and Surrey.
“Effective immediately, ash material (such as logs, branches and wood chips) and all species of firewood cannot be moved outside the regulated area without permission from the CFIA,” the agency said in a statement last month.
“If you need to move ash material, please contact your local CFIA office to request written authorization.”
A Vancouver Park Board spokesperson told CBC News in a statement that, throughout August, it had been treating ash trees along public streets with the injectable insecticide TreeAzin.
“The insecticide is injected directly into the base of the tree, which targets only insects which feed on the tree,” the spokesperson wrote.
“The treatment program is intended to prolong the lives of Vancouver’s ash trees, but does not guarantee full protection,” they added.
The spokesperson said that the neighbourhoods with the highest level of beetle detection were downtown and Strathcona, specifically near Coopers’ Park and Strathcona Park.
Emerald ash borer infestations have been identified in a few more areas this year, according to the spokesperson, including around Sunrise Park in East Vancouver.
In the statement, the spokesperson said it was difficult to conduct reliable surveillance on how many beetles exactly were in the city, and branch sampling was highly labour-intensive and could cause false positives.
“Many ash trees, including some that are positive, are still outwardly very healthy,” they said.
“We have not seen mass die-off of ash trees occurring.”
