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The jackpine forests in Alberta and going east could be the next course on the mountain pine beetle’s menu.
By Tony Kryzanowski
Does the dreaded mountain pine beetle find jackpine as tasty as lodgepole pine? The answer is “yes,” based on the scientific data gathered to date. The conclusive evidence may show up soon now that the beetle is at the doorstep of Canada’s vast pure jackpine forest. That’s according to Canadian Forest Service (CFS) entomologist David Langor who, along with colleague Adrianne Rice, has been studying the susceptibility of jackpine to a mountain pine beetle infestation for the past two years.
Evidence of the beetle in the jackpine forest east of Slave Lake, Alberta will represent the crossing of an important threshold. To this point, there have been no recorded incidents of beetle in jackpine in the boreal forest, according to Langor, although it wouldn’t surprise him. He says the beetle has proven quite adaptable, feasting on a variety of pine species in its native habitat west of the Rocky Mountains. It has even been found to have infested spruce trees in areas where it is currently imbedded and the pine resource has been exhausted.
“It obviously has a very broad diet,” says Langor. “I would say that jackpine fits quite comfortably within that range and it should be quite readily accepted by the mountain pine beetle.”
Should the beetle establish a foothold in pure jackpine, this could have major consequences for the Canadian forest industry, as jackpine is one of the most plentiful and commercially valuable softwood species in the Canadian boreal forest. It stretches from Eastern Alberta to the East Coast.
“If I was a Saskatchewan woodlands manager, I would be looking at my old jackpine stands closest to Alberta and trying to do something about them over the next few years,” says Langor. “The beetles certainly prefer mature stands.” Pine over 80 years old has less vigor and may be more prone to succumb to a beetle attack.
The beetle introduces deadly fungi into an infested tree, leaving behind a blue stain discoloration in the wood that many BC and Alberta sawmills must now contend with when marketing their lumber. Research has shown that it’s the fungi that actually do the most initial damage to the tree, as they block the flow of water and food, literally choking the tree. Trees have been known to be dead within two weeks of infection.
Last summer, evidence of mountain pine beetle was found as far east as the Swan Hills, south of Slave Lake, which is in the lodgepole pine/jackpine hybrid zone. The pure jackpine forest begins a mere 100 kilometres away, near Athabasca. To reach the Swan Hills, large numbers of beetle took flight from northeastern British Columbia, with some beetles propelled about 300 kilometres due to favourable wind currents through Rocky Mountain passes, and were blown half way across Alberta.
When they showed up near Grande Prairie at the Alberta border, many local residents described their impressions of the flight as “the beetle rain.” Models of beetle migration and field surveys conducted by both CFS and members of the mountain pine beetle scientific and response team at the Alberta Department of Sustainable Resource Development indicate that the most likely advance of the beetle into the pure jackpine forest will be east of Slave Lake. That’s because the beetle population in a triangle from Whitecourt to Valleyview and east to Slave Lake may not have experienced the massive mortality this past winter as did beetles in the Grande Prairie region.
Models and field sampling conducted by CFS in the Grande Prairie region indicate that a late November cold snap resulted in about 99 per cent beetle mortality in that region this past winter. The same is true of the Peace District across the border in British Columbia. Further south in the Spray Lakes/Canmore region, beetle mortality was lower, meaning that area was very susceptible to a major beetle outbreak this summer.
While high mortality in the area around Grande Prairie is good news for the immediate future, that does not preclude repeated clouds of the beetle showing up in Grande Prairie as a regular summer occurrence until the insect runs its course in neighbouring British Columbia.
Langor has been studying the beetle in Alberta since the last outbreak occurred in the 1980s, in the southern section of the province. “Ever since then, we’ve been speculating about what might happen during the next outbreak, and with the spectre of climate change on the horizon, if the beetle might actually get up to the boreal zone and then eventually switch to jackpine,” he says. “Indeed, we have seen over the past few years the beetle moving further and further north in both BC and Alberta.”
Langor's work is being financially supported by the federal Mountain Pine Beetle Initiative, the provinces of Alberta, Saskatchewan, Manitoba, and Ontario, as well as the United States Forest Service, showing how seriously government leaders are viewing the threat of the beetle.
Part of the research has focused on whether there are any structural or chemical attributes in jackpine that might deter the beetle migration eastward. “Chemically, jackpine is not that different from lodgepole pine, so I would expect that they would be equally attractive,” Langor says. The fact that they interbreed is an indication of just how closely related they are.
The bark texture on the jackpine is quite a bit coarser and has more flakes, which is bad news. “As far as we know, that’s better for bark beetles in general for creating sites to initiate galleries.” One noticeable difference between lodgepole pine and jackpine is the phloem thicknessthe light coloured inner layer of the bark that is the food conducting tissue within the tree. It’s a nutritionally rich tissue where the beetle breeds. The phloem layer in mature lodgepole pine is between 2.5 and three millimetres thick, but is only about one millimetre thick in jackpine. Thick phloem results in bigger beetles able to fly further, survive better and lay more eggs.
“One millimetre is not thick enough for the entire body of the beetle to be immersed in the phloem,” says Langor. “So they have to chew through the harder outer bark and sapwood, both of which are presumed to be less nutritionally valuable. The thickness of the phloem layer has shown historically to influence the number of offspring that the mountain pine beetle produce.”
Laboratory research has borne this out, producing beetle offspring about 10 per cent smaller than their parents. “What we saw is that jackpine is not as bad a host as we thought it would be based on phloem thickness,” says Langor. “The beetles still seem to do pretty well in there, almost as well as in mature lodgepole pine.”
Climate will definitely influence the beetle’s migration east. There are areas east of Alberta that still experience long periods of cold, winter weather. However, Langor points out that the beetle isn’t influenced so much by cold weather, as the timing of the cold weather compared to the beetle’s preparedness for it.
“In fact, all you need is a couple days of minus 30 degrees Celsius at the right time of year and the beetle can suffer high mortality,” he says. “I have personally seen that scenario while doing my PhD work in southern Alberta. It resulted in a collapse of the beetle during the last outbreak, which ended in 1985.”