Technical Abstract: Biological control using hymenopteran parasitoids presents an attractive alternative to insecticides for reducing infestations and damage from the Indianmeal moth (Plodia interpunctella) in retail and warehouse environments. We examined the potential for using combinations of the egg parasitoid Trichogramma deion Riley, and the larval parasitoid Habrobracon hebetor (Say), for preventing infestations of P. interpunctella in coarse ground cornmeal, as well as the influence of packaging on parasitoid effectiveness. Treatments included one or both parasitoids, and either cornmeal infested with P. interpunctella eggs or eggs deposited on the surface of plastic bags containing cornmeal. Habrobracon hebetor had a significant impact on P. interpunctella, lowering populations by about the same magnitude in both open and bagged cornmeal. In contrast, T. deion did not suppress P. interpunctella in open cornmeal. However, when released on bagged cornmeal, T. deion significantly increased the level of pest suppression over bagging alone. When H. hebetor was added to bagged cornmeal, there was a significant reduction of live P. interpunctella compared to the control (70.6%) with a further reduction observed when T. deion was added (96.7%). These findings suggest that, in most cases, a combined release of both T. deion and H. hebetor would have the greatest impact because, even though packaging may protect most of the stored products, there are usually areas in the storage landscape where poor sanitation is present.