What Is Spruce Budworm?

The eastern spruce budworm (Choristoneura fumiferana) is a native insect that causes major damage to Maine’s spruce-fir forests on a regular cycle.  Spruce budworm caterpillars feed on the buds and needles of fir and spruces.  Under normal (endemic) conditions populations of this insect are so low that spruce budworm is hard to find. Periodically the budworm undergoes a population outbreak (epidemic) and becomes so abundant that serious feeding damage occurs. During epidemics defoliation is heavy enough that affected trees produce very little wood and many thousands of trees die.