Amanda Vaughan
Northern News Services
Published Friday, September 7, 2007

YELLOWKNIFE - Yellowknife's birch leaf miner population is now officially on borrowed time.

It might be a lot of borrowed time, like five to ten years of it, but that's beyond the point.

Signs of birch leaf miner damage on birch leaf from a tree near Yellowknife City Hall, seen in 2002. - NNSL photo file photo

The capital's birch trees have been wearing the unsightly effects of the pesky birch leaf miner since the early 1990s, according to Scott Digweed from Natural Resources Canada.

Digweed, who is based out of Edmonton, was a researcher for a project funded by the US department of agriculture which fought the miners with the Lathrolestes Luteolators wasp, a small stingless insect that lays its eggs on miner larvae, in Anchorage, Alaska, where the bugs had also over-stayed their welcome.

"One of the reasons we brought the project to Yellowknife was to establish another abundant population of the parasites," Digweed said, referring to the Lathrolestes Luteolators wasp.

The wasps made their way to Fort Smith and Hay River on their own, by riding nursery trees, Digweed suspects, and reduced the birch leaf miner population there.

Digweed said that once the wasps reach a high population level, the miner population can crash pretty quickly, but nobody should hold their breath.

"It can take as long as five to 10 years before they reach that level," he said.

The wasps are a single minded "predator" in the manner that they will only lay their eggs in birch leaf miner larvae, according to Digweed, so they are very effective at finding the larvae, even when the supply is scarce.

He said that even in cases where both populations are long-term, there doesn't seem to be any evidence of the wasps dying out and allowing the miners to re-infest.

Yellowknife's birch trees now have a fighting chance, since this is the first year that Digweed has discovered evidence of the wasps over-wintering in town.

"I am very pleased, since this is the last year which we have funding for the project," said Digweed.

Digweed said he had been releasing wasps in Yellowknife for the last couple of summers, and setting small sticky-traps each year before each release, to see if any made it through. This summer, he found a single male wasp in the trap.

"It appears that they have established in Yellowknife," said Digweed.

After seeing an indication that the wasps are surviving, Digweed released another batch this summer, which will be the last.