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Cold winter in Metro Vancouver could reduce impact of garden pests

Randy Shore, Postmedia Network

Dr. Allan Carroll is a Professor of Insect Ecology at the UBC Department of Forest and Conservation Sciences. Carroll is holding an indigenous-to-BC ground beetle, at UBC Thursday, January 12, 2016. (Jason Payne/ Postmedia Network)

Dr. Allan Carroll is a Professor of Insect Ecology at the UBC Department of Forest and Conservation Sciences. Carroll is holding an indigenous-to-BC ground beetle, at UBC Thursday, January 12, 2016. (Jason Payne/ Postmedia Network)

This winter's cold temperatures probably won't deliver a knockout blow to the chafer beetle larvae ravaging Metro Vancouver lawns. Nor will the frozen ground provide gardeners much relief from the wireworms that devour the tender roots of their backyard veggies.

But migratory birds might just put the local insect populations back in balance, according to Allan Carroll, a professor of forestry at the University of B.C.

Be warned, though, your lawn may take a beating in the process.

Chafer beetle larvae are nestled deep in our lawns, just waiting for spring's warmth and a chance to devour the roots of our grass, pupate and finish their life cycle. Likewise, the wireworms that overwinter in our lawns and gardens are well-adapted to the cold, particularly if there is an insulating layer of snow on the ground.

But that's not to say the cold weather won't produce some benefit for homeowners who have been battling a rising tide of pests in recent years.

"This winter we have now is not an anomaly, if you think about it, it's what winter used to be like," said Carroll. "We used to get these winters more often when I was a kid and it gives our seasons a more defined seasonality."

After a warm winter, insects recover early, feed, pupate and carry on with their lives before migratory birds return from their winter homes. Cold winters tend to keep bugs and their larvae in the ground longer, long enough to make them vulnerable to hungry birds.

"A lot of plants and animals are dependent on the cues they get from a good solid winter to go dormant and wait till spring to start doing their business," he said. "In the case of insects — which are an important source of food for migratory birds — after a warm winter they have finished up before the birds come back."

A long, cold winter will better synchronize the insect life cycle with the arrival of birds looking for food.

"Plus, some insects that don't necessarily belong here, but have survived because of the mild winters, could well be nuked by this cold snap," he added. "That could be some good news for gardeners."

The Vancouver Sun's gardening expert, Steve Whysall, also notes that birds and other animals do a fine job of eating all the chafer beetle larvae, though they will tear up your lawn as they root out the pests. Once they have done that work, you can install a healthier lawn, which is more resistant to infestation or consider non-grass-based ground covers.

rshore@postmedia.com