The following pages describe the relationship between army cutworm defoliation and the growth and yield of winter wheat. The research that went into this manuscript resulted in the development of a scale for rating army cutworm damage. The result is a good example of the efficiency of visual damage ratings versus actual damage measurements. In addition, a new method of rearing army cutworms was developed which greatly increased survival of the first instar larvae. This method may be helpful in other cutworm rearing programs. Finally, the results indicate that a damage rating of 6 and above (approximately 40 to 50% defoliation per plant) in a greenhouse does result in decreased yield. Such damage is equated with a level of about 4 to 6 fifth-instar cutworms per plant. This level of infestation is not meant to be an economic injury level for army cutworms on winter wheat, for, the greenhouse conditions under which these tests were run are different than those in the field.