A story about Douglas-fir beetle in the Cariboo
By Max Winkelman
For Douglas-fir trees, 2017 was a rough year in the Cariboo. Not only did wildfires scorch hundreds of thousands of hectares, many of which contained Douglas-fir trees, a windstorm on May 23, 2017, knocked over trees throughout the area. Meanwhile, something less immediately noticeable has been pestering Douglas-fir trees specifically.
Douglas Fir Beetle
Douglas-fir beetle is a dark brown to black insect with reddish wing covers and is about half a centimetre long as described by the Ministry of Forests, Lands, Natural Resource Operations and Rural Development (FLNR).
It has a one-year lifespan and usually prefers weakened trees, such as those blown over by the wind.
Their main flight occurs in May and June, while a second flight may be made in July and August.
They’re native to North America and traditionally haven’t been too much of a concern but occasionally populations increase to the extent that it infests and kills large numbers of healthy trees.
On the rise
For multiple consecutive years, the area affected by Douglas-fir beetle has been on the rise, with the affected hectares in the Cariboo growing from 2,659 hectares in 2013 to 69,418 hectares in 2016.
There was a slight decrease in 2017, to 65,446 hectares.
“It can be assumed that the total area of mapped infestation would have been higher were it not for the Elephant Hill and Alexis Creek/Hanceville fires, which consumed large areas of infested Douglas-fir forest and/or masked evidence of Douglas-fir beetle attack,” according to the FLNR’s 2017 Overview of Forest Health Conditions in Southern British Columbia report.
There are multiple reasons for the increased Douglas-fir beetle levels, says Pat Byrne, 100 Mile House district manager for FLNR.
“What has happened though is, through a number of circumstances, whether it’s a lack of fires and I say that seriously in spite of last year, we’ve discouraged fires for many of these fir ecosystems. We have some conditions out there on the land base where the stands have grown up stressed, whether it’s overstocking or the result of drought conditions or whatever it is and [Douglas] fir beetle takes advantage of those things.”
Experts are quick to point out, the levels near those of other well-known beetle infestations.
“It’s been an ongoing increase over quite a few years now. Even then, it is still quite small compared to the recent mountain pine beetle infestation or to the current spruce beetle infestation near Prince George,” says Dr. Dezene Huber from the University of Northern British Columbia.
For comparison, in 2017, there were 372,483 hectares affected with spruce beetle in the Omineca region.
However, the Douglas-fir beetle may do quite well again this year, says Byrne.
“Last summer would suggest to me that [Douglas] fir beetle did quite well and we should expect to see an increase,” he says. “I’m anticipating this year we’re gonna see that the populations may very well be on the rise in areas that didn’t get burned and I’m expecting we’re gonna see some new infestations arise within the areas that were burned where there’s still green douglas fir because they would have been stressed.”
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