In this study, we investigated behavioral and physiological traits that allow competition between an introduced parasitoid and its native counterparts, using a model system that consisted of a native pest species, evergreen bagworm Thyridopteryx ephemeraeformis L. (Lepidoptera: Psychidae) and its parasitoids in central Illinois. We focused our investigation on four parasitoid species, three of which were native to the area: the generalist ichneumonids Itoplectis conquisitor (Say) and Gambrus ultimus (Cresson), and the torymid Monodontomerus minor (Ratzeberg). However, the most abundant parasitoid in the system was the exotic ichneumonid Pimpla disparis Vierick, also a generalist parasite. P. disparis was originally introduced in North America for control of gypsy moth and has apparently spread in Illinois far ahead of the gypsy moth front. We collected and identified potential alternative hosts of the parasitoids to map their developmental course throughout the seasons and to identify over-wintering hosts. We conducted experiments to determine each species’ competitive abilities in both lab and field settings. We also examined how volatiles of flowering plants affect rates of parasitism for each parasitoid species. Our evaluation of the impact of P. disparis on the natural enemies complex of evergreen bagworm in central Illinois provides important information for improving the safety and efficacy of classical biological control, particularly potential methods for minimizing non-target effects.
Species 1: Hymenoptera Ichneumonidae Pimpla disparis
Keywords: biological control, non-target effects
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