Sudbury·Backroads Bill

Spruce budworm eating its way through northeastern Ontario forests

A Spruce budworm infestation is on its way and it appears to be entering a new outbreak phase in northeastern Ontario, according to CBC Sudbury’s backroads adventurer Bill Steer.

It may be hard to believe that this insect is a natural part of the forest ecosystem, Backroads Bill explains

The brown on the trees shows up after the larvae finish eating. The larvae "poop”, along with the dead needles, are intertwined at the end of the twigs in a web that holds the brown-coloured pupa. That is the protective cocoon or hardened case. All of this material turns red as it dries and oxidizes. (Bill Steer)
A Spruce budworm infestation is on its way and it appears to be entering a new outbreak phase in northeastern Ontario, according to CBC Sudbury's backroads adventurer Bill Steer.

The Spruce budworm is the most destructive pest of spruce and fir forests in North America, notes Steer. The larvae are wasteful feeders as they only eat partial needles and then move on to other needles.

Steer's research shows the last outbreak in Ontario peaked at about 18 million hectares in 1981.

It may be hard to believe that this insect is a natural part of the forest ecosystem. And another wave is coming.

How do the scientists know?
Taylor Scarr is a provincial forest entomologist with the Ministry of Natural Resources and Forestry. (Hilary Duff/CBC)

"The defoliation in Ontario was expected, based on increasing defoliation in 2014, and a significant increase in the number of moths caught in pheromone traps in northeastern Ontario in 2014," Taylor Scarr, a forest health specialist with the Ministry of Natural Resources and Forestry, told Steer in an interview.

The rise in moths is also likely connected to similar defoliation that is occurring in Michigan and Quebec, he said.

North Bay red spruce stands under attack

Scarr said Spruce budworm helps drive forest succession and fire cycles. When its preferred hosts (balsam fir and white spruce) reach about 40 years of age, they become most susceptible to the budworm.

"The trees killed by the budworm become more susceptible to fires, which tend to be more severe in forests with large numbers of dead trees," Scarr said.

"After the fire goes through, the forest regenerates to younger stands of conifers or hardwoods. This provides habitat for plants and animals such as fireweed, pin cherry, moose, and certain bird species that prefer younger forests."

Scarr told Steer that one of the areas where budworm is causing severe defoliation is in the red spruce stands near North Bay.

"These stands are biologically unique, representing one of the few areas in Ontario — besides a few stands in Algonquin Park — where this species can be found in the province."

The spruce budworm has been in the area for decades, forestry experts say. Around 2005, the population “exploded” between Sturgeon Falls and Sudbury, extending north to River Valley and beyond. (Bill Steer)
Currently, aerial mapping is being done by the MNRF Forest Health Monitoring program. So far this year, defoliation is occurring in Dubreuilville, Kapuskasing, and Timmins. Defoliation is also occurring north and east of North Bay towards Temagami and Temiskaming, near Sturgeon Falls, on Manitoulin Island, and near Sault Ste. Marie, including St. Joseph's Island and Thessalon.

To read more about what Backroads Bill has learned about the Spruce budworm, visit Bill Steer's website. Bill Steer can also be contacted at or found on Facebook at Steer to Northern Ontario.


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