Laboratory Evaluation of Pupal Parasitoids for Control of the Cornsilk Fly Species, Chaetopsis massyla and Euxesta eluta

SIMPLE SUMMARY: Cornsilk flies are highly destructive flies that cause damage to developing cobs of corn, particularly sweet corn. Eggs laid on cornsilk hatch and larval feeding on the kernels under the protective outer leaves results in damage and often render cobs unsaleable. Mature larvae leave the cobs and pupate outside of the cob. The aim of this study was to evaluate the potential of known fly pupal parasitoids for use as biological control agent for these flies. Five species of commercially available parasitoids were evaluated, and all developed in cornsilk fly pupae and caused significant mortality. Our results indicated that these parasitoid species warrant further consideration for their potential (mortality range 46.1–98.5%) against cornsilk flies in the field. ABSTRACT: Cornsilk flies are serious pests of sweet corn through damage to cobs and secondary fungal establishment. As pupae are generally outside the infested cob on the ground, there can be potential for use of pupal parasitoids for control. Two species of gregarious parasitoids, Muscidifurax raptorellus and Nasonia vitripennis, and three species of solitary parasitoids, Spalangia endius, Spalangia cameroni and Muscidifurax raptor, were evaluated against pupae of the two cornsilk fly species, Euxesta eluta and Chaetopsis massyla. House fly pupae, the most common host for most of the parasitoids, were included for comparison. All of the parasitoids killed and successfully parasitized pupae of the two cornsilk fly species at rates that were similar to house fly pupae. Adult parasitoids that emerged from cornsilk fly hosts were somewhat smaller than parasitoids reared from house flies and had proportionally fewer females. These parasitoids, which are widely and commercially available for filth fly control, warrant further consideration for their potential against cornsilk flies in the field.