Pine beetles
Chainsaws, research are weapons in the fight against insects’ spread.
SLAVE LAKE — On the front lines of Alberta’s war against the mountain pine beetle, the weapons are chainsaws and biological data.
The soldiers in this battle focus their attention only on areas in which they have a good chance of preventing the beetles from spreading — the so-called level one control sites where forestry staff cut and burn infected trees. In other areas, staff simply monitor the beetle-infected trees each spring, using information from hundreds of sites to plan next winter’s campaign and help companies log specific areas to control the beetle’s spread.
The so-called pine islands south of Slave Lake — groves of pines surrounded by aspen — are among these areas that can’t be saved, and that is where provincial forest health officer Dale Thomas and technician Jenn MacCormick were earlier this week, cutting out “cookies” of bark and cambium layers from infected trees to count beetle larvae.
Early indications in the month-long survey suggest that in this area at least, the beetles are doing fine.
“Look at that, there are lots of live ones here,” said Thomas as he peeled away bark at the base of one pine tree.
Dozens of white, rice-sized larvae moved as they began to die from premature exposure to the air. By July they will be hardy and ready to fly, and kill more trees.
“You’ll find most in the first ten feet of the tree, and more survive lower and under the snow, where they are protected from temperature variations,” he said.
The crew cuts two cookies on the south side and two on the north side of the survey trees.
Inside many of them are bored vertical pathways that show the track each female beetle moved — usually a J-shape as they enter the tree’s nutrient-rich cambium layer under the bark and travel upwards.
They leave a trail for frass, which is basically glued sawdust containing dozens of eggs. When they hatch in 10 days, the tiny larvae travel sideways, creating galleries that end in tiny carved-out chambers where they mature through the four stages of development. The cycle starts during a two- to three-week period in late July when mature females emerge from the trees and find new homes — usually the next tree or within perhaps a 50-metre radius.
Alberta’s beetle infestation originated in B.C. when two flights arrived, most recently in 2009. Unusual weather patterns raised the low-flying beetles high into the atmosphere and blew them over the mountains. When they land on a mature pine tree, the females give off pheromones to attract males, and then bore under the bark.
The trees are not defenceless — they react to the beetles by trying to flush them out with sap.
The first signs of a tree under attack are these fingernailsized sap bubbles.
But if more than a few beetles attack at once, the tree is usually overwhelmed.
And to further hasten the tree’s demise, the beetles carry a blue fungus that spreads quickly in the cambium layer and restricts the tree’s ability to flush the beetles.
If the weather is mild through the fall, the larvae development will be well advanced by winter. And if it is one without wide variations in temperature, fewer insects will perish.
Aside from weather and a lack of fresh trees to kill, woodpeckers may be the biggest threat to the beetles.
“They are always chipping away, and there can be piles of bark at the base of trees. I have seen large sections of trees stripped bare by the birds, and parts of the tree untouched,” said Thomas.
“So they must be able to sense the beetles, or hear them, below the bark.”
Every year the province surveys about 300 sites like this patch south of Slave Lake.
The vast area west of Slave Lake and north of Hinton is Alberta’s largest and most valuable pine forest, and the results from the spring ground surveys and fall aerial surveys allow foresters to determine which pine areas to log promptly to slow the beetles, and which areas need the level one treatment that sees trees logged and burned to ash.
Surveys in the pine islands areas are simply for the purpose of data collection. The distinctive sites are the result of the massive Chisholm fire of 2001 which burned most of the coniferous forest in the area. The surviving patches of pine stand taller and greener than the rapidly growing sea of aspen trees that have since sprung up across the onceburned landscape.
On this island of pine, Thomas figures all the trees will be dead within a few years. But since they are surrounded by a young aspen forest, there is nowhere the insects can go when the pines are gone.
The prime target for beetle control is north of Slave Lake, where large areas of pine are at risk.
“That is where the department will put its effort, that’s where we have a chance to succeed.”