Cold weather in late winter/early spring is very welcome

(If you want the mountain pine beetle to be slowed down)

Jennifer MacCormick
For the Lakeside Leader

Mountain pine beetle (MPB) larvae spend 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 as winter progresses and have the highest amount of it in their systems during the coldest parts of our winters. Therefore, they are more cold-hardy in January than they would be in May or November.

This cold snap (in March) will have caused greater mortality than had the temperatures remained mild. Prior to the cold snap, overwinter mortality model predictions for the Slave Lake forest area were low, between 20 per cent in the south west and 70 per cent in the central and northern areas. However, model predictions now indicate higher levels of mortality – around 70 to 90 per cent. Keep in mind that these predictions are for beetles above the snow pack. Any beetles below the snow pack are insulated against those cold temperatures.

Evidence from research done on Alberta beetles indicates that we need levels of mortality around 95 per cent for population growth to slow. At this point we’d need continued cold temperatures around and below -35 to for this to happen.

We know that MPB are able to recover after significant levels of mortality and so control measures continue to be important to reduce their spread.

MPB populations are already distributed through much of Alberta’s pine forests. We don’t have any indication of great risk that these populations will grow rapidly in the coming year. The risk is low because of the recent cold winters and summers, and our continued control efforts.

The survey and control program is complete in the Slave Lake Forest Area for the season. There were 1,388 sites ground-surveyed and 2,409 trees controlled. Although the spring surveys can help us understand the potential for populations to expand that summer, they don’t really tell us about overwinter mortality. We will have the complete picture after the offspring overwintering right now complete their life-cycle in the summer and we do our surveys in the fall.

Mountain pine beetle
Photo courtesy Alberta Ag & Forestry

Share this post

Post Comment