Spruce budworm is a native insect that is considered by many as the most serious pest affecting the forests of eastern Canada. Every 30-40 years populations of spruce budworm increase resulting in an outbreak or epidemic. Such an outbreak is currently occurring in Quebec and populations are beginning to rise in New Brunswick and the rest of Atlantic Canada.

The spruce budworm spends the winter as a tiny larvae hibernating in the cracks and crevices on the branches of trees. In spring the larvae emerge and begin feeding on the current-year needles and buds of fir and spruce trees. Feeding continues throughout most of May and June and once they have finished feeding the larvae (brown caterpillar about 2 cm in length) will pupate and emerge as adults (greyish-brown moth) within a couple of weeks. The moths will mate and the female will lay up to 200 eggs, usually on the underside of fir and spruce needles. The eggs hatch in about two weeks and the young larvae find a hiding place to spend the winter thus completing the one-year cycle.

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A Spruce Budworm Infestation

Spruce budworm infestations are extremely destructive to balsam fir and spruce and, if unmanaged, can cause significant mortality. Outbreaks typically last up to 10 years, during which the caterpillars repeatedly eat the new foliage of fir and spruce. It is important to note that it takes 4 to 6 years of severe infestation before a tree is killed and that although spruce budworm populations in New Brunswick and the rest of Atlantic Canada are rising they are not at outbreak condition. However, if an uncontrolled outbreak was to occur, stemwood growth could be reduced by as much as 90% and tree mortality of 85% for mature balsam fir and 35-40% for young fir and mature spruce could occur.

As of 2016, the spruce budworm outbreak in Quebec measured 7.0 million hectares, an area roughly equivalent in size to the province of New Brunswick. Significant spruce budworm populations are only a few kilometres north of New Brunswick on the Gaspé Peninsula.

Why it’s Important to Manage the Infestation

Every day, New Brunswickers venture into our province’s forests to work, live and play. Protecting and keeping our forests healthy is important for our way of life and our economy. Finding safe ways to proactively treat spruce budworm populations before it becomes an infestation is important.