In the spring the caterpillars begin to eat the new tree buds of coniferous trees, such as spruce and fir. Severe outbreaks have occurred about every 30 to 60 years. To control the damage caused by this insect over 8 million hectares of forest have been sprayed with pesticides. While this spraying has helped control the spruce budworm, the pesticides have been found to damage the ecosystem. Food organisms like mayflies and caddisflies that are important sources of food for trout can be severely reduced by pesticide spraying.
Nature has a way of helping to control an outbreak of the spruce budworm.
During an infestation, birds that feed on caterpillars have a tremendous increase in food supply. This allows them to have more eggs and the population can increase rapidly. This increase in the bird population helps reduce the number of caterpillars. The Cape May Warbler is one bird that multiplies rapidly when the spruce budworm is abundant. It becomes an important predator of the spruce budworm.