Impact of Hyperparasitoids onCotesia glomeratain Southwestern Virginia

Abstract

This study was initiated to determine the impact of hyperparasitism on Cotesia glomerata (L.) (Hymenoptera: Braconidae), an established gregarious endoparasitoid of Pieris rapae (L.) (Lepidoptera: Pieridae). C. glomerata pupae were sampled in field crops of cabbage and broccoli to determine rates of hyperparasitization for each hyperparasitoid species. Two of the principal parasitoids recovered were Conura torvina (Cresson) (Hymenoptera: Chalcididae) and Tetrastichus ( Aprostocetus ) galactopus (Ratzeburg) (Hymenoptera: Eulophidae). The impact of hyperparasitoids was measured per clutch as well as per individual C. glomerata. This may provide insight into the potential impact of existing hyperparasitoids on closely related solitary parasitoids like Cotesia rubecula (Marshall) (Hymenoptera: Braconidae). Both C. torvina and T. galactopus had little effect on the overall C. glomerata population. The impact of hyperparasitoids per clutch appears to be more appropriate for estimating a hyperparasitoid's potential impact on solitary hosts. The threat from C. torvina was minor, but T. galactopus may affect the establishment of a newly introduced population of C. rubecula.