Abstract
Four species of hyperparasites, two of which attack both Cotesia glomerata (L.) and Cotesia rubecula (Marshall), larval parasites of the imported cabbageworm, Pieris rapae (L.), were collected in samples from 1986 to 1988. Hyperparasites recovered from C. glomerata were Tetrastichus galactopus (Ratzeburg) (Hymenoptera: Eulophidae) (6.2%), Catolaccus aeneoviridis (Girault) (Hymenoptera: Pteromalidae) (1.1%), and Spilochalcis torvina (Cresson) (Hymenoptera: Chalcididae) (0.8%). The former attacked the larval stage; the latter two attacked the pupal stage. Hyperparasites recovered from C. rubecula were S. torvina (29.7%), T. galactopus (6.8%), and a pupal hyperparasite, Isdromas lycaenae (Walker) (Hymenoptera: Ichneumonidae) (1.4%). The level of hyperparasite activity between C. glomerata and C. rubecula was significantly different. Hyperparasitization averaged only 8.1% for C. glomerata (L.) from 1986 to 1988, but averaged 37.9% for C. rubecula (Marshall) from 1987 to 1988. During the early to mid-season of 1988, hyperparasite activity was low and C. rubecula was the dominant parasite; but by mid-season, hyperparasite activity against C. rubecula increased to 100%, causing its populations to crash. C. glomerata then became the dominant parasite of P. rapae . We were unable to recover C. rubecula in our broccoli plots during the 1989 or 1990 growing season. We hypothesize that hyperparasites, especially S. torvina , appear to be a primary limiting factor in the establishment of C. rubecula in southwestern Virginia.
Published Version
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