Shades of Green: Earth's Forests -- Pests

The spruce budworm is one of the most destructive insects in northern coniferous forests (forests which are highly valued by people for their wood, which makes excellent pulp and paper products). The spruce budworm is actually not a worm, but a caterpillar, and mainly damages balsam fir, not spruce. The caterpillars feed on the leaves, buds, and twigs of trees, and a severely infested stand can become completely defoliated.

Severe outbreaks of insect pests, however, are rare, and occur much less frequently in natural forests than in "managed" ones. Most insects, including the spruce budworm, have their own natural enemies, which can usually keep their numbers low enough that they do not cause a problem.

Many insects hollow out tunnels in wood of dead trees to create nests -- the holes here were formed by carpenter ants, which live in the wood but do not eat it, as is commonly thought. Photo by Maya Walters

Insects can cause the most damage in planted "forests". In eastern Canada and the United States, the forests were once a diverse mixture of red spruce, Eastern hemlock, birches, pines, maples and other trees, in total over 20 species. Today, this forest is gone, and has been replaced by plantations of balsam fir and white spruce -- the two species preferred by the spruce budworm. These plantations are perfect habitat for this insect, which has reached epidemic populations. But the spruce budworm isn't the problem -- it existed in the ancient natural forests as well. The problem is the "monoculture", the huge single-species plantations, which allowed the insects to multiply to such huge numbers.

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