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Alarming infestation brewing in Ontario: arborist

May 23, 2024  By Sandi Krasowski, Local Journalism Initiative Reporter

Photo: Annex Business Media.

A forester and arborist is sounding the alarm on increasing spruce budworm infestations across Ontario’s Thunder Bay area and expects a further surge this season.
Vince Rutter, owner of Rutter Urban Forestry, works with his team in the city pruning and removing trees as well as providing treatments to control insects and improve plant health.
“This year’s spruce budworm infestation leaves me with big concerns about tree health that start with losses to individual landscape trees and can lead to widespread tree mortality, which results in economic losses to the forestry sector, but worse, can lead to fuel for forest fires,” Rutter said.
In the region, there are many spruce and fir trees and Rutter said he noticed significant feeding damage last year. This year he expects more damage and defoliation, a trend continuing for the next few years at least.
“I’m very concerned that the increased fuel load of dead fir and spruce trees will lead to some very explosive forest fire conditions,” Rutter said.
He pointed out the Kamview Nordic Centre as an example of a forest area that is heavily populated with fir trees, of which he expects 90 per cent mortality over the next few years.
“It’s not unreasonable to be very alarmed by this,” he said.
Rutter also noted that this outbreak is not climate-change related and populations of spruce budworm tend to explode every 30 years.
He said spruce budworms emerge in the spring, begin mining last year’s needles and then move into the buds as they expand. As of May 21, the feeding is only noticeable if one looks closely and this will change in a couple of weeks. Rutter expects to receive many calls from alarmed tree owners as they begin to notice the damage.
Currently, the small five-millimetre larvae can be found in the expanding buds. They will continue feeding for the next few weeks, and “in an outbreak” will eat all of the new needles. Feeding damage will become obvious in mid-June.
Rutter called the caterpillars “messy and wasteful eaters” that leave webbing and partially eaten needles behind.
“The caterpillars will finish feeding in June and then pupate to become moths,” he said. “These moths will emerge in the summer and lay eggs on spruce and fir twigs where the larvae overwinter.”
Moths during an outbreak are noticeable. If the wind is quiet, their flight and feeding are audible.
The caterpillars prefer balsam fir and white spruce, and during an outbreak, they can also be found feeding on black spruce and sometimes tamaracks, he said.
“Younger healthy white spruce can withstand several years of defoliation while older white spruce or spruce experiencing stress may not survive and can die after a few years of the infestation,” Rutter said.
Rutter added that Balsam fir does not tolerate spruce budworm infestations well and mortality is usually high in all age classes. Dead fir trees will be noticeable across the region this summer. Many spruce trees will also either look dead or die.
Residential spraying can be effective in controlling larvae, however widespread aerial sprays are required for control of the landscape.
Rutter said there are no aerial sprays planned for 2024 in the Northwest region, according to his research with the Ministry of Natural Resources and Forestry.

Sandi Krasowski is a Local Journalism Initiative reporter for The Chronicle-Journal. 

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