none The effects of kairomone pattern and preconditioning on parasitization rates of fall armyworm larvae, Spodoptera frugiperda (J.E. Smith) by C. (= Apanteles) marginiventris (Cresson) were investigated in the laboratory and greenhouse using a hexane extract of frass and actual fall armyworm frass. Parasitization rates increased 55 and 26% in Petri dishes and on corn seedlings, respectively, when the entire experimental area was sprayed with the frass extract. Applying the extract in spots resulted in a 20-30% reduction in parasitization compared to treating the entire area. Spot application produced significantly better parasitization rates compared to the control treatment. Exposing the parasitoids to actual fall armyworm frass resulted in apprx 50% greater retension in the release area and an increase of apprx 60-75% in the number of parasitoids searching. C. marginiventris parasitized factitious hosts topically treated with an extract of fall armyworm frass.