Will cold snap devastate pine beetle?

When it comes to that cold snap in January, its impact on the mountain pine beetle won’t be known for several months.
And even then, says forest health officer Jennifer MacCormick, it’s tough to tell.
“Since I’ve been doing this job, some years the numbers go up and some years they go down.”
Last year, the number of trees in the district infected by the beetle was down.
“Last year we controlled [destroyed by burning, in other words] about 4,400 trees,” MacCormick says.
“A couple of years ago it was 20,000 trees.”
This winter, the number of sites identified by aerial surveys in the summer was 630. Surveys continue.
The mountain pine beetle larva spends the winter under the bark of pine trees. They are able to do this because they produce ‘antifreeze’, a chemical in their blood that helps them tolerate cold temperature. They build up the antifreeze and have the highest amount of it in their systems during the coldest parts of winter.
Therefore, they are more cold-hardy in January than in May or November. In order to cause a decline in the population, 95 per cent of the beetles would have to die.
The models indicate that at a temperature of -35C under the bark, enough will die to stabilize population growth. Under-bark temperature and ambient air temperature can be significantly different. The under-bark temperature depends on several factors, such as the insulating effects of snow, bark thickness and water content of the tree.
The effects on pine beetle populations from this latest cold snap won’t be known until the population forecast surveys are done this spring.

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