Parasitism and Utilization of Imported Cabbageworm Pupae by Pteromalus puparum (Hymenoptera: Pteromalidae)

Pteromalus puparum</it> (L.) parasitized 64.1 and 32.5% of imported cabbageworm, Artogeia rapae</it> (L.), pupae collected from pesticide-free cabbage field plots in 1983 and 1984, respectively, in southwestern Virginia. Parasitism was most pronounced in the latter part of the season. In commercial cabbage fields, 67.2% of overwintering pupae were parasitized. High percentages of parasites successfully emerged as adults, indicating efficient host utilization. Most parasite mortality within the host occurred in the larval stage; mean adult parasite emergence per host for 1983 and 1984 was 52.3, with a 1:1 sex ratio. However, variability of male parasites per host was double that of females. Females weighed twice as much as males, suggesting a compensation of number for size. P. puparum</it> did not parasitize either host sex discriminately, and equal numbers of male and female parasites emerged from both host sexes. Laboratory studies suggest that host/parasite ratios and length of host/parasite exposure time are important considerations for laboratory rearing of P. puparum</it>. Suboptimal conditions result in unparasitized and mutilated hosts.