Finney et al. (1982) reported on the susceptibility of the 4th to 6th larval instars and pupae of Choristoneura fumiferana (Clemens) to Heterorhabditis heliothidis (Khan, Brooks and Hirschmann). This report describes the susceptibility of the first three larval instars to the nematode. First-instar larvae search for suitable sites where they spin hibernacula in which they molt and overwinter as second-instar larvae. Most third-instar larvae burrow within the balsam fir buds. All these stages occupy cryptic habitats to which delivery of chemical pesticides is a problem. Rhabditid nematodes, which can actively seek out a target insect, may prove a more useful control agent under these circumstances.