Correct identification of early instar larvae of fall armyworm (Spodoptera frugiperda) and cotton bollworm (Helicoverpa zea) is needed since these species have different thresholds for treatment, and potential controlling insecticides have varying activity on them. Visual observations with a hand lens (20X magnification) of first instar larvae did not reveal any gross differences between species except the fall armyworm reacted very defensibly to probing. The cotton bollworm was docile. Second instar cotton bollworms had longer and coarser bristles and more prominent hairs than the fall armyworms; black bumps (tubercles) at the base of any spines on the bollworm were more raised. Although the insect growth regulator, Dimilin^® (diflubenzuron), exhibits little activity on the cotton bollworm due to the nature of its feeding habits, it was shown to control fall armyworm infestations. Fall armyworm activity was demonstrated in the field using a single application (1998), multiple low dosage applications (1998), and in combination with a pyrethroid (1996, 1998).