A Long-Term Survey of Parasitoid Species Composition and Parasitism of Trichoplusia ni (Lepidoptera: Noctuidae), Plutella xylostella (Lepidoptera: Plutellidae), and Pieris rapae (Lepidoptera: Pieridae) in Minnesota Cabbage

Field studies were conducted near Rosemount, MN, during the years 1991–1994, 1996–1997, and 1999–2003, to assess the diversity of and parasitism by larval and pupal parasitoids of cabbage looper, Trichoplusia ni (Hübner), imported cabbageworm, Pieris rapae (L.), and diamondback moth, Plutella xylostella (L.). Species composition, parasitism rate, and species abundance (Hill's N1) were determined for each pest species. Voria ruralis (Fallen), Copidosoma floridanum (Ashmead), and Compsilura concinnata (Meigen) were the dominant parasitoids of T. ni; Phryxe pecosensis (Townsend), Cotesia glomerata (L.), and Pteromalus puparum (L.) are the dominant parasitoids of P. rapae; and Diadegma insulare (Cresson) is the dominant parasitoid of P. xylostella. In addition, the first records of the introduced parasitoid, C. concinnata, parasitizing T. ni and P. rapae, and Cotesia rubecula (Marshall) parasitizing P. rapae are documented for Minnesota.