SUPPRESSION OF OSTRINIA-NUBILALIS BY TRICHOGRAMMA-NUBILALE IN SWEET CORN

We conducted inundative release experiments with Trichogramma nubilale (Hymenoptera: Trichogrammatidae) to suppress Ostrinia nubilalis (Lepidoptera:Pyralidae) in sweet corn (Zea mays): two experiment during O. nubilalis first generation and three experiments during second generation. Five measurements of ear and stalk damage were used to assess O. nubilalis control in treated and untreated plots within each experimental field. In one experiment during second generation, natural O. nubilalis populations were sufficiently high to demonstrate that the parasitoids (three releases totaling 4.4 million parasitoids per ha) parasitized an estimated 57.4% of the placed O. nubilalis egg masses and reduced the mean number of O. nubilalis larvae per ear by 97.4%, the number of tunnels per stalk by 92.9%, and the number of larvae per stalk by 94.3% in the release plot. Ear damage in this experiment was suppressed to meet acceptable standards for use in cut-corn commercial processing. Larval mortality was apparently density independent, which implies that density-dependent larval loss would not compensate for egg parasitism by T. nubilale.