A small native moth is attacking lodgepole pine forests along the Continental Divide near the border of Banff and Kootenay national parks, turning a sea of green trees red.
Northern lodgepole needle miner larvae are living in the pine needles, with the last significant outbreak in the 1950s when it affected over 750 square kilometres in Banff and Kootenay national parks.
Jed Cochrane, Parks Canada’s fire and vegetation ecologist for Lake Louise, Yoho and Kootenay, said the trees would not grow much this year due to the infestation, but believes they are unlikely to die.
“It’s a native species and it’s very cyclical in its population. It goes through big booms and busts and we’ve historically had some big booms,” he said.
“One of the biggest was in the 1950s and we had another in the 70s or 80s. This one could get bigger than the one in the 50s.”
The moth has a two-year life cycle and it overwinters as larvae in old needles. Larvae migrate when hatched and quickly bore into individual needles in spring. Migration increases as larvae grow until fall and then spend the winter in needles.
In the second spring, feeding is resumed and migration to new foliage begins. Moths emerge in summer and eggs are laid, usually within hollowed needles, and hatch around September. New larvae bore into needles, feed until winter and then become dormant.
“It’s a miner, which means it burrows its way into one end of the needle and mines its way down the needle. It doesn’t go into the bark, it just eats the needle,” said Cochrane.
“It’s a two-year life cycle and every two years it flies and this is a flight year. Just prior to flight year is when you see significant amounts of red,” he added.
“It will emerge in August and September and fly, and so two years from now, unless the population is knocked back, we would see another big year.”
At present, the most notable outbreaks are along the Continental Divide near the boundary between Banff and Kootenay national parks. There are also patches of red trees between Castle Mountain and Lake Louise, even some around Lake Louise.
Long-sustained outbreaks of the insect occur sporadically in the western United States and Canada, usually in extensive stands of mature lodgepole pine. Although defoliation may be severe, the biggest effect is a reduction in tree growth.
During epidemics, larvae can damage every needle on all lodgepole pines over large areas. In some areas when there’s been an outbreak, tree growth has been reduced by 90 per cent and trees have died.
Extreme cold or wind, as well as parasites, helps keep this native insect in check.
In terms of climate change, Cochrane said a warmer climate would likely make it easier for the miner to prolong its outbreak.
“If there’s heavy rain, cold temperatures, heavy winds, snow, or anything like that, it will decimate the population and it would drop back down to almost nothing,” he said.
“If you get a couple of years where you don’t have that weather in the fall, that population is going to build up.”
Unlike management of mountain pine beetle through prescribed fires, Cochrane said Parks Canada does not do anything to manage northern lodgepole needle miner.
“You’re really at Mother Nature’s whim and that’s not a bad thing,” he said. “We know it’s part of the food web and a lot of bird species key in on it and feed on it.”
