Odd looking bands with a sticky glue on them adorn many trees across Greater Victoria this time of year.
They serve as a preventative measure to trap winter moths and prevent them from laying eggs in the tree canopy.
October and early November is the crucial time to apply a new band and glue as the winter moth females, which look like a moth but are flightless, dance up the tree.
It’s a successful strategy but also an onerous task.
“They’ve killed a lot of trees in Oak Bay [and Greater Victoria] and the bands really do stop them,” said Oak Bay’s municipal arborist Chris Paul.
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The winter moth showed up a few decades ago and began taking down Garry oaks and other trees in the region.
During the fall, the females travel up the tree and, through a mating process with males, eggs are laid in the canopy near the leaf buds.
Come spring, the larva on an infested tree will devour the entire new growth of leaves. Then they will repel down and pupate in the grass. Most trees recover with a second flush of leaves but after a few cycles, it depletes the tree of its reserve stores and it progressively stresses the tree, and can kill it.
Paul has put hundreds of bands on trees and has tried various strategies.
“They aren’t a true caterpillar, they’re more like an inch worm with legs,” he said. “The females can’t fly, they walk up the tree. The males fly up and meet them.”
The non-toxic sticky glue is available at nurseries and is about $20 for a jar. Oak Bay gets theirs from Borden Mercantile. Paul apples it with a paint mixer.
Paul uses a thin layer of foam and tightly bound packing tape to force the winter moth on to the outside of the tape, which is slathered in the sticky glue. Alternatively, he has used a cardboard based wrap, though he finds they deteriorate quickly under the Victoria’s acute, heavy fall rain.
“The sticky glue can also be applied directly but it creates a black smear on the bark that lasts for many, many years,” Paul said.
In Paul’s experience he’s learned that banding is particularly effective on stand alone trees.
“If you have a lot of trees you have to band them all because they’ll travel through the canopy,” Paul said. “They can repel down onto the branches of other trees.”