Parallorhogas pyralophagus (Marsh) is the principal parasitoid of Mexican rice borer, Eoreuma loftini (Dyar), the primary pest of sugarcane in south Texas. Insect resistant transgenic sugarcane producing Galanthus nivalis agglutinin (GNA) was developed to improve control of E. loftini. The present laboratory study addressed whether transgenic sugarcane adversely affects parasitism of E. loftini by P. pyralophagus. Females of P. pyralophagus preferentially probed, drilled, and parasitized E. loftini larvae fed artificial diet based on conventional sugarcane versus larvae fed diet based on transgenic sugarcane. Activity levels of E. loftini were reduced when fed diet based on transgenic sugarcane, but no differences were evident in frass volatile profiles. Overall, the results suggested a positive association between larval activity level and likelihood of parasitism, which may render E. loftini larvae feeding on transgenic sugarcane less susceptible to parasitism by P. pyralophagus. However, it was concluded that this may not significantly affect control of E. loftini because (1) while E. loftini larvae that are most susceptible to transgenic sugarcane may be less prone to parasitism by P. pyralophagus, they are less likely to cause severe crop damage and reproduce successfully; and (2) those E. loftini larvae least susceptible to transgenic sugarcane, and therefore more active and damaging to plants, may be more prone to parasitism by P. pyralophagus.