Cold snap hits pine beetles where it hurts

The return of cold weather isn’t all bad news. Unless you’re a mountain pine beetle.

The return of cold weather isn’t all bad news. Unless you’re a mountain pine beetle.

Some Albertans, like Duncan MacDonnell, are celebrating the plunge back into frigid digits as the beetle, the most damaging insect pest of pine trees in western North America, is more of a fair weather friend.

“The scientific knowledge we have right now says the best way to kill a beetle is for temperatures to get down to at least -40C for at least 24 hours, preferably 48 hours,” said MacDonnell, a public affairs officer with Alberta Environment and Sustainable Resource Development. “But this is more ideal in November, when they’re still at the early stages of their life cycle and not really winter-hardened yet.”

For this time of the year, the best weather weapon against the beetle is warming periods snapped up by deep cold spells, much like what Central Alberta and the beetle-infected forests around Slave Lake, Grande Prairie and Hinton have been experiencing these past two weeks.

“A week and a half ago we had temperatures in the highs. Now we’re in -20C in most parts. Tremendous fluctuations in temperature are in our favour. It’s called the yo-yo effect, warming followed by cold followed by warming and this fools the beetles into converting some of their natural glycerol, or antifreeze, into energy so then when you return to that cold snap, they’re not as hardy as before,” MacDonnell said.

The result is the potential for good “overwinter kill” of the pesky insects.

Researchers are digging deeper into what exactly the yo-yo effect means for the beetle, MacDonnell said, with work recently commissioned with Natural Resources Canada at a lab in Victoria.

The Alberta government surveys from May until June to assess the number of pine beetle larvae that survived winter. This will give them an indication of the population trend, MacDonnell said.

Last spring, surveys were conducted at 135 sites and samples taken from 825 trees across the province. The results showed relatively high beetle overwintering success compared to previous years, with only a few pockets of lower success.

An area being especially monitored this winter is in the forests south of Grande Prairie, which are still at a high risk of beetle spread from the large number of infested trees surveyed in 2013.

Additionally, crews conduct aerial surveys of “red attack trees” every fall, looking for pines with red hues, which shows they have been killed and left by the pests.

Control work continues throughout the winter and involves methods such as cutting and burning and single tree removals, MacDonnell said.

More than 90,000 infested trees were removed over last winter and six million hectares of Alberta’s pine forests are at risk of infestation, according to Alberta Environment.

The beetle has ravaged forests in B.C. for over the past two decades and swept into west-Central Alberta in 2006. The black, no-bigger-than-a-grain-of-rice beetle was also discovered for the first time north of the 60th parallel last winter in a small number of trees north of where the N.W.T., Alberta and B.C. borders meet.

MacDonnell said there have been small beetle infestations since the 1940s in the southwestern part of Alberta, with the last one in 2001. That area is now effectively under control, so much so that it was not even surveyed last spring.

The good news is that the beetles haven’t “really spread to the east as much as they’re concentrating in pockets that they were already at,” MacDonnell said.

“But the lessons learned from previous beetle epidemics is you never underestimate the beetle.”

rfrancoeur@bprda.wpengine.com

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