Spruce budworm is a native insect that is considered by many 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. An outbreak is currently occurring in Québec and populations are rising in Atlantic Canada. In an effort to curb an outbreak, researchers are testing a new approach to keep spruce budworm populations low and our forests healthy.

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 were to occur, tree growth could be reduced by as much as 90%, tree mortality of 85% (in mature balsam fir) and 35-40% for young fir and mature spruce.

As of 2020, the spruce budworm outbreak in Québec covered over 13.5 million hectares. Significant spruce budworm populations are just north of New Brunswick on the Gaspé Peninsula.

Life cycle

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. 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.

Why it’s important to manage the infestation

Every day, Atlantic Canadians 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 treat spruce budworm populations before it becomes an infestation is important.