They web the new foliage together loosely and feed inside, where they are somewhat protected from predators and other enemies. Western spruce budworm egg mass on needle. Western spruce budworm larva. Each body segment has two conspicuous pairs of white spots. About 40 days after feeding begins in the spring, usually about the end of June, the larvae pupate inside feeding webs or on foliage.
Adults emerge a week or so later and the cycle is complete.
There is one generation per year. Damage and Associated Impact Budworms are important because they can eat all the new growth produced by host trees. The new needles are most important in producing food for the tree, so the immediate effect of defoliation is a reduction in growth. To the homeowner, defoliation mostly means a loss of aesthetic value. As defoliation progresses, both in extent and duration, more significant impacts are likely.