The continuity of food demand has caused modern agriculture to be heavily dependent on chemical inputs. Plant growth regulators (PGRs) are naturally occurring or synthetic compounds that have the potential to control pest insects through their chemosterilant activity. Along with pests, non-target organisms such as parasitoids in agroecological systems are likely to be influenced by indirect contact via their hosts or direct contact with hosts and plants at the tritrophic level. This study demonstrated the dietary effects of PGR indole-3-acetic acid (IAA) on hemolytic activity and phenoloxidase activity in stored product pest Galleria mellonella L., 1758 (Lepidoptera: Pyralidae) and parasitoid Pimpla turionellae L., 1758 (Hymenoptera: Ichneumonidae). The significant increase in hemolytic activity in G. mellonella and P. turionellae hemolymph were observed in 500, 5,000 and 10,000 ppm IAA-treated groups. Phenoloxidase activity in G. mellonella hemolymph significantly decreased with all IAA doses compared to control, however, the reductions in phenoloxidase activity in P. turionellae hemolymph were significant between 500 and 10,000 ppm. Since IAA interacts with both host and parasitoid immunity, it should be used with caution in agricultural areas with high host-parasitoid population.