Most mountain pine beetles in Alberta killed over winter, data shows

Frigid temperatures this winter have killed off more than 90 per cent of the mountain pine beetles in Alberta forests, new scientific data suggests.

But experts won't know until this spring if the death rate is high enough to actually stop the destructive bugs from continuing to spread to new healthy trees

Computer models run by the Canadian Forest Service on Thursday indicate that 95 per cent of the beetles have died in southern Alberta and the mountain parks because of the harsh winter. About 90 per cent have died in northern Alberta.

"What we can say categorically is that this cold snap will buy some time," said Barry Cooke, a scientist with the federal department.

"There will be a reprieve for southern Alberta and the mountain parks. We are confident of that. But will it be one year or three years or five years of reprieve? Nobody knows."

The challenge is that the die-off rate for the beetle must hit a staggering 97.5 per cent to keep the rice-sized critters from flying to and destroying more pine trees.

Cooke said other biological factors, such as beetle-eating birds and other insects, could add to beetle mortality rates.

More definitive information won't be available until Alberta work crews actually hit the ground in May to visually inspect and start disposing of infected trees at 300 sites throughout the province.

Bugs hardy, mobile

Last September, the province estimated there were almost 200,000 infected trees, with almost 75 per cent located north of the Trans-Canada Highway.

The conventional wisdom is that the bugs in one infected tree can spread up to 10 new trees in the summer.

The Alberta government said it is cautiously optimistic about the federal computer model data, which is based on recorded winter temperatures.

It's believed that five days of 40 C cold can kill the beetles, but less severe cold snaps can also be lethal in the late fall or early winter.Severe temperature fluctuations can also short-circuit the beetles' internal antifreeze system that protects them from the cold.

But the bugs, many of which are the offspring of beetles that flew over the mountains from British Columbia a few years ago, have proven to be very hardy and very mobile.

"We like hearing those numbers but we can't say for certain that what the model is predicting is going to happen," said Erica Lee, senior forest health officer for Alberta Sustainable ResourceDevelopment.

"Even with 90 or 95 per cent mortality we still can't walk away from any beetle-infested sites because it will continue to grow. We can't give up the fight."

No reason to lower guard

Alberta estimates that the beetle threatens about 60,000 square kilometres of its pine forests.

Over the past three years, the province has spent $210 million to fight the pests that have already ravaged much of British Columbia's pine forests.

There is more money earmarked to fight the bugs in Alberta in the coming fiscal year, but the amount won't be released until the provincial budget is tabled April 7.

Cooke also cautioned that a high mortality rate is no reason for anyone to lower their guard.

He said if the numbers turn out to be correct it should be considered one victory in a long, ongoing battle. And he said a big die-off will need to be followed up by a strong campaign this summer to remove and destroy infected trees.

All it could take is a mild winter next year for the mountain pine beetles to flourish again.

"When this insect system is down, kick it hard," he said. "It makes sense to kick it when it's down."