SASKATOON -- It will have to get a lot colder to kill the mountain pine beetle, according to Rory McIntosh, an entomologist and insects and disease expert with the forestry branch of the Ministry of Environment.

It has to be – 40 C for a sustained period of time to kill the beetle larvae that spend the winter under that bark of trees.

The mountain pine needle is not found in the northern Boreal Forest of Saskatchewan. There is a native population in Cypress Hills but their distribution and population dynamics are affected by cold weather.

“For the beetle to be successful it colonizes and attacks trees all en masse,” said McIntosh.

The mountain pine beetle remains under surveillance. It is a native invasive bark beetle and threatens the forest and forestry industry in the boreal forest in the north half of Saskatchewan.

“It really hasn’t been cold enough yet to have any substantial impact on forest insects and certainly the ones that we are concerned with, but the winter is still young so I’m hoping for it to go much, much colder for a sustained period of time.”

Cold temperatures in 2019 helped decrease the population, however there were some areas in the forests less affected by the cold where the beetle survived.

“Even last year, when we had those extensive periods of cold weather there were pockets that were affect substantially but other pockets were the beetles survived. There are always these residual pockets where beetles can and will survive.” McIntosh said. “Did it affect them last winter, yes, it did, but not everywhere and not completely.”

Native defoliator species like spruce budworm and the forest tent caterpillar moth have evolved in Saskatchewan forests and adapted to cold temperatures. The outbreak cycles of the spruce budworm are predictable; McIntosh said the next serious damage from the spruce bud worm will happen 15 years from now. The species last peaked in 2002.

Ticks are also affected by the winter weather. The species overwinters under the snow in the upper layer of the forest floor and in grasslands. Snowpack acts as insulation and protects them by from damage. Typically, if there is very little snow the nymphs that are overwintering will freeze and die, he said.