Emerald ash borer survives Winnipeg's extreme winter weather

An invasive beetle species is more adaptable to harsh winter weather than previously thought, says a study out of London, Ont.

The emerald ash borer can survive in temperatures that dip as low as50, and that's not good news for theash tree population in Winnipeg and throughout Manitoba, Brent Sinclair says.

Sinclair, a biology professor at Western University, and four other researchers published their findings in the Current Research in Insect Science journal on Wednesday.

A previous study saidthe Asian beetle, which arrived in Winnipeg in 2017, froze to death once the mercury dropped to about28 C.

However, recent experiments byMeghan Duell, the post-doctoral researcher on the project, found some of theinsects from Winnipegdidn't freeze until temperatures reached an average of46 following the polar vortex that slammed parts of Canada, including Manitoba, and the midwestern United Statesin 2019.

Sinclair called the findings quite surprising.

"[They're] as cold-tolerant as just about any insects on Earth and certainly ascold-tolerant as you need to be to survive in most places on Earth even Winnipeg," Sinclair said Thursday.

The beetles either evolved to survive the harsh Winnipeg winters in just a few years, or they have the ability to quickly change their physiology to respond to the frigid weather, he said.

Sinclair saidthe latter is the primary factor.

"They survive right up until the point that their body fluids freeze, so the trick is to allow themselves to cool down and not freeze," he said. "It seems to be they are doing this by having very concentrated blood."

The borer dehydrates a lot and accumulatesglycerolin itsblood, which Sinclair said worksthe same as antifreeze in your vehicle'sradiator.

The study says cold tolerance of larvae has not been explored in depth, but Sinclair believes larval cold tolerance is "an essential component" of the borer persisting in Winnipeg.

"If they had been super cold-tolerant as prepupabut had to overwinter as larvae and couldn't do that, then that would have been a problem and they probably wouldn't have survived," he said.

Ash doomed: entomologist

Although the study says the borer has survived the past few Manitobawinters, it remains to be seen how much of a barrier our cold winters are to their spread within the province,Jordan Bannerman said.

"It is quite remarkable that these beetles can survive such extremes.These beetles surviving in a climate much colder than in their native range is a testament to how flexible the biology of insects can be," said Bannerman,an entomology instructor at the University of Manitoba.

The invasive species has only been confirmed among ash trees in one Winnipeg neighbourhood, St. Boniface, Bannerman said.

The city has taken precautions against the beetlesince its initial detection, and Bannerman believes that proactive approach has been key to slowing the expected spread of the borer.

The city has approximately 350,000 green ash trees, which compriseclose to one-third of the urban forest canopy.

Ash trees are important riparian habitat because they stabilize the banks of many streams and rivers in the province, and provide shade in parks and on campsites, Bannermansaid.

While the borer population hasn't increased or decreased, the ecological impact of the beetles will be felt in the future, as will the economic impact of chopping down dying trees and planting new trees, he said.

"Big picture:ash is not going to be in good shape," he said.

"We still do expect, although it may be slower, that this beetle willremove most of the ash from the landscape in Manitoba."