Insects feast on Whitehorse willows after unusually warm, dry spring

The willow blotch leaf miner appears to be having a banner year in Whitehorse, likely because of hot, dry conditions in the city this spring.

Willow blotch leaf miners leave willow leaves blotchy and discoloured, but unlikely to kill the tree

Bruce Bennett explains the effect of the willow blotch leaf miner, which causes discolouration in willow leaves. (Anais Elboujdaini/Radio-Canada)

This spring's warm, dry weather in Whitehorse has led to a feeding frenzy for insects that chow down on willows in the city.

The willow blotch leaf miner — one of the most destructive defoliators of willow in North America — appears to be having a banner year in Whitehorse. It's likely because of the hot, dry conditions in the city this spring, explained Bruce Bennett, the co-ordinator of the Yukon Conservation Data Centre.

The miner begins as a small insect and grows into a moth as an adult. It was first recorded in Yukon in 2007. 

Bennett first noticed the insects himself after spending time outside this past weekend, and soon heard about it from others who had noticed the same thing. 

"I walked into my backyard and came inside, and the next thing I knew I had little green worms all over me," he said. "I have never had so many phone calls and emails." 

Bruce Bennett shows leaves that have been eaten through. This spring's warm weather has led to a feeding frenzy for willow blotch leaf miners in Whitehorse. (Anais Elboujdaini/Radio-Canada)

The willow blotch leaf miner is similar to the Aspen miner, which has been present in Yukon for quite some time. The willow blotch miner is similar to its Aspen cousin, but it attacks leaves differently, Bennett explained. 

"It forms botches or patches, dark, discoloured patches on leaves," he said. "It's eating a chamber out of the leaf, then it's coming out of the leaf and dropping down on a silken thread, very similar to what was happening with the Aspen leaf miner."

Bennett says the miner appears to have little effect on willows that moose in the territory most often eat. Also, any infestations of the miner are unlikely to kill the willows unless this level of infestation occurs for many years.

"This is a native species that has taken advantage of the weird spring weather we received," he said. "It's an interesting phenomenon."

Written by Alex Brockman, based on a report by Radio-Canada's Anais Elboujdaini