The spruce budworm is a native insect that periodically kills large numbers of balsam fir and spruce trees across eastern Canada. Generally speaking, it is neither a “good” or “bad” guy. Instead, it is a natural disturbance that kills mature forests, allowing young forests to regenerate in their place. Similar to forest fires, these outbreaks are all part of a natural ecological cycle; the budworm cycle often results in mature balsam fir being killed and replaced by young balsam fir.

However, from an economic standpoint spruce budworm is definitely a “bad guy”.  Numerous independent scientific studies across eastern Canada, published in peer reviewed journals, continue to tell us just that. These studies show that typical spruce budworm outbreaks kill up to 85% of mature balsam fir and from 35-40% of mature spruce and immature fir. Studies during the past (1967-1992) budworm outbreak in Quebec estimated that tree mortality losses were 238 million cubic meters of timber and probably an equal amount in reduced growth, with an estimated commercial value of $12.5 billion.

Additional studies focusing on the New Brunswick forestry sector have quantified the effects of an uncontrolled spruce budworm outbreak on the provincial wood supply over the next 40 years. Dr. Chris Hennigar, a former PhD student at UNB, modeled plausible scenarios based on past budworm outbreaks for the 3.0 million hectares of Crown land in NB and reported cumulative harvest reductions of 18% and 25% under moderate and severe budworm outbreaks, respectively.  Under these same outbreak scenarios, Dr. Wei-Yew Chang (another former UNB PhD student) found that the economic loss to the NB economy over 30 years was projected to be $3.3 billion and $4.7 billion. Up to 30% to 50% of these projected reductions could be avoided through foliage protection treatments, while replanning harvest and salvaging dead timber could reduce losses by an additional 1-18%.

The economic downturn under the no budworm control scenario was projected to lead to the loss of as many as 1,900 jobs every year for the next 30 years.

For a firsthand look of the current spruce budworm in action one need look no farther than  the current 4.2 million hectares of outbreak in Quebec, currently only a few kilometers from the New Brunswick border.

We believe we can prevent this from happening in New Brunswick. The Healthy Forest Partnership ( is working on research into an early intervention strategy aimed at identifying and treating spruce budworm ‘hotspots’ to control the outbreak. This is done by applying organic Bacillus thuringiensis, or Mimic growth regulator, to forest hotspots. These treatments help drive budworm populations back down to low levels, limiting the spread of an outbreak.

Ultimately, all decisions about how we manage spruce budworm are made using the best available scientific data. With this information forestry experts from government, industry, and academia can continue to create balanced strategies that take into account the short-term and long-term environmental and economic impacts of an outbreak.

Prof. David MacLean

University of New Brunswick

Faculty of Forestry and Environmental Management