Monday, 16 January 2017 08:00

Mountain pine beetles still prevalent in Alberta

Written by  Stephanie Labbe
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Mountain Pine Beetles (MPB) have been a troubling issue for Alberta tree populations over the years. Winter generally helps decease the populations of the pine beetles, but it won’t completely eliminate them.

When left unmanaged, pine beetle populations can kill large numbers of Alberta’s pine resource.
Mike Undershultz with Alberta Agriculture and Forestry, says pine beetle can easily kill six-million hectares of pine trees valued at more than $8 billion.
He adds, of the 25 major forest companies operating in Alberta, 14 rely on pine to continue operations.
As it’s not realistic to be completely pine beetle free, infestation management has helped decrease populations.
“MPB are now endemic to much of the province and we are working to reduce spread and minimize impacts. Aggressive action has been and will … continue to be effective in achieving these goals,” says Undershultz.
Generally speaking, the number of pine beetle-infested trees located at the priority sites for control haven’t changed much since last year.
However, Undershultz says aerial and ground surveys conducted to date this year have noted some regional shifts in population numbers. There have been decreases in populations of pine beetles in the Grand Prairie and Whitecourt Forest areas overall.
There have been significant increases in population in the Edson and Slave Lake Forest areas and a moderate increase in the Calgary Forest Area, in the Bow Valley.
“Very cold and sustained winter temperatures of minus 40 degrees Celsius and below … at the right stage in the beetle life cycle is the most significant cause of beetle mortality,” adds Undershultz. “We have not seen widespread and sustained cold snaps of this nature in Alberta for a number of years.”
The cold weather southern Alberta has seen recently may have some impact in some areas, but there are a lot of factors that determine levels of mortality from cold.
Undershultz says different stages of beetle development have different levels of cold tolerance and beetle development can be variable across the province. As well, micro-climate differences may create variable levels of mortality even in localized areas.
Snow acts as an insulator for beetles, so the depth of snow will also, to some degree, influence mortality levels.
By taking all of the factors into consideration, Undershultz says it’s difficult to accurately predict what the cold has done, or will do this winter. For that reason, Undershultz says they tend not to speculate, but rather assess the survival success rates of beetle populations in the spring once mortality-causing weather events are past.
“The spring population forecast surveys … measure the proportion of live larvae and adults that survived the winter compared to the number of beetles that attacked the tree in July and August of the previous calendar year. Results from this survey will be available in late spring or early summer of 2017,” adds Undershultz.
MBP is currently the most destructive forest pest in the province. Although the distribution of MPB covers the majority of Alberta, he says there’s a wide range in the levels of MPB-caused tree mortality.

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