- Atwood, C. E.
- Gray, D. E.
The adult of the spruce budworm (Cacoecia fumiferana Clem.) is a small moth, mottled, gray or reddish brown in color, with a wing-spread of about three-fourths of an inch. Appearing on the wing during late June and July, these moths lay their eggs on the needles of balsam spruce and sometimes larch and other trees; balsam and white spruce, however, are the preferred hosts. These eggs hatch into the young budworms which at once and without feeding spin a small silken shelter in a crevice or other protected spot on the tree and pass the winter there. The budworms are dormant until May when they emerge from hibernation and attack the newly opened buds and young needles of the tree, feeding and growing rapidly for about a month. When the new foliage is depleted, the older needles are attacked but not to the same degree; however, the final result is more or less complete defoliation of the tree and frequently death in a longer or shorter period, depending on the severity of the attack. Balsam is usually killed by two or three consecutive years of defoliation, white spruce by three to five while black spruce is seldom killed but may be retarded in growth.