By Megan Roth
The pesky beetle causing vast quantities of lodgepole pine trees throughout western Canada to die is on the decline in the Cypress Hills area.
Roughly 260 trees were found to be infected by the mountain pine beetle in the Cypress Hills area, down from last year when 287 trees were infected.
In 2013 an estimated 440 trees were found to be infected in the area.
Brian Poniatowski, forest insect and disease program specialist with the Ministry of Environment, said out of the current 260 infected trees 221 were found in the West Block and 39 were found in the Centre Block.
“The distribution this year was very similar to last year,” Poniatowski said.
Last year, a tactic for controlling the spread of the beetle called pheromone baiting was used. Pheromone baiting is a process which uses a synthetic pheromone to draw the insect to specifically marked trees. This is supposed to keep them from moving on and infecting other healthy trees.
“We found it to be very successful, the numbers are down again,” Poniatowski said.
The use of the synthetic pheromone is an effective way of controlling the spread of the insects and the infected trees. The use of the pheromones was once again used this year on 50 trees in the Cypress Hills area.
“It is a very effect way to combat the issue,” Poniatowski said.
The beetles themselves are not the large cause of trees dying. The mountain pine beetles feed on the blue stain fungus in their larval and pupal forms, which covers their head and mouth. When the insect becomes an adult there are remains of the fungus on them which they then carry to a new, healthy tree.
The blue stain fungus kills living tree cells and prevents the production of the tree’s natural defence, resin. The lack of natural defenses make it easier for the mountain pine beetle to burrow into the tree and lay its eggs.
Adult mountain pine beetles feed on a tissue within the tree called phloem. It is the young form of the insect that feeds on the blue stain fungus.
Because of the push for forest fire suppression, trees in the forest are getting older and older. While this may sound like a good thing, it is also problematic. Bark beetles, like the mountain pine beetle, prefer older trees as it is easier for them to invade the tree. Older trees also have more room for large amounts of beetles to colonize. The bark is thicker as well, which gives the insects more protection from weather and predators.
With forest fires comes new birth for trees. The younger the tree means less mountain pine beetles in the area. Because of this, some areas in North America that have wide spread mountain pine beetle problems have used prescribed burning.
Prescribed burning is a controlled forest fire started by a professional.
But the amount of trees infected in Cypress Hills is too small to use prescribed burning. Instead, infected trees are cut down and burned, effectively killing the insects burrowed in the tree before it can migrate to another.
The Ministry of Environment tried to determine the mortality rate of the insects through winter by sparing some of the infected trees from being cut down and burned last year.
“Over the winter survey 2014-2015, the weather was not severe enough to naturally control the beetles,” Poniatowski said.
To naturally control the beetles, temperatures would have to exceed -40 C under the bark.
“This does depend on the time of year as well. If it was colder earlier in the winter, they may die at a warmer temperature like -30 degrees,” Poniatowski said.
Natural collapses of an outbreak are usually due to the depletion of the food source and extremely cold temperatures. Unfortunately, due to milder and milder winters the beetles are surviving the winters. They are even traveling further north, which traditionally has a climate too cold for the insect to survive.
“We know that the winters haven’t been killing them off,” Poniatowski said.
The infected trees that were left over the winter are burned later in the spring. They are left to see if the weather was enough that year to naturally control the beetles.
“They will still be burned down, its just a matter of when,” said Poniatowski.
With the continual decline of infected trees, those who are working toward ending the outbreak are taking it a year at a time.
“It is hard to say what the numbers will be like next year. All we can do is take it a year at a time.
“We know that our program is seeing positive results,” said Poniatowski.
On top of pheromone baiting this year, Poniatowski said they will be cutting down the vast majority of the infected trees this winter and burning them. There will be a small sample of trees left to measure the mortality rate over the 2015-2016 winter.