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War on the birch leaf miner

City bringing up Hay River wasps to defend birch trees

Jennifer McPhee
Northern News Services

Yellowknife (Aug 14/02) - The City of Yellowknife is bringing special wasps from Hay River this fall to take on the birch leaf miner -- the pest that's draining nutrients from birch and poplar trees.


The birch leaf miner causes the leaves of birch leaves to turn brown, not usually causing serious damage. However, if an infected tree experiences repetitive attacks, does not get enough moisture and is attacked by other insects, the branches could perish. - Merle Robillard/NNSL photo

Adult wasps lay eggs on the worm's larvae. The following spring, newly-hatched baby wasps eat the larvae.

The city originally planned to buy 200 wasps from Edmonton at a cost of $3.75 each. However, samples of birch leaf miners were collected in Hay River and Yellowknife by putting heavy duty fly-paper pads in trees. Then, they sent the samples south over the winter for analysis.

Surprisingly, the tests found the wasps naturally occur in Hay River. "Because they are occurring naturally in the North, we're going to use that species rather than introduce one from down south," said City of Yellowknife community services director Grant White.

"We're going to go to Hay River and collect leaf samples that have wasps in it and lay them around our trees."

The tiny wasps will then wage war on the birch leaf miners.

This fall is considered a test, said White. The city will release wasps around Soomba K'e Park and city hall. Then if further sticky paper tests find the wasps are doing they're job, the city will bring up more.

But birch leaf miner infestation isn't as bad this summer, said White.

"Last year it already looked like fall because all the leaves were falling off the trees."

The insects inflict damage to the leaves of birch trees. The first signs of infestation are light green or grey spots. The spots eventually turn into brown blotches. As the insects feed between the surfaces of the leaves, the brown blotches increase in size and spread, covering most of the leaf.

The birch leaf miner is not native to Canada. The insect was inadvertently transported from Europe to North America in the early part of the 20th Century.