Nature is turning the tide in the battle against a massive infestation of spruce beetles in the Yukon.

Scientists monitoring the spread of the beetles, which have destroyed an area of forest about two-thirds the size of Prince Edward Island, said the infestation in southwest Yukon may soon be over.

Nothing has seemed to slow the beetles' advance — first detected in Kluane National Park in 1994. Since then, the insects have consumed nearly 350,000 hectares of forest in the park, the nearby Shakwak Valley and beyond.

Now, researchers say aerial observations over the last two years show the beetles' spread has slowed, and may soon collapse completely.

"The numbers were way down, although the area was still large, I'm suspecting somewhere between 40,000 and 60,000 hectares," said Rod Garbutt, a forest health technician with Natural Resources Canada, about last year's survey.

"But within those areas it was almost exclusively very light attacks."

Killing of trees declining

Garbutt,  who has been monitoring the attack since it began, says less than five per cent of trees were killed in areas infested last year, a marked decline from past years.

He says that over time, parasites, disease and predators have put pressure on the insects. Poor weather slowed the bugs' important spring advance as well, as has the natural chemical resistance the trees have to the insects.

"These all sort of pile up on top of one another and the beetle population declines as a result," said Garbutt.

While the insect population will collapse, it won't be the last the area has seen of the beetles.

"The infestation as we witnessed will essentially be over, however there is always going to be a remnant population of spruce beetle in the forest," he said.

Older and sickly trees will still fall prey to the beetles, but healthy trees should be able to repel their attack.

Garbutt said the total collapse of the population should be complete within two years, ending Canada's largest infestation of spruce beetle on record.