Mass rearing of two larval parasitoids of Helicoverpa spp. (Lepidoptera: Noctuidae): Netelia producta (Brullé) and Heteropelma scaposum (Morley) (Hymenoptera: Ichneumonidae) for field release

Parasitoids are becoming an increasingly important part of our biological arsenal in Integrated Pest Management strategies against major insect pests like Helicoverpa armigera (Hübner). Inundative or supplementary releases of parasitoids have been successfully used in the past to help manage insect pests in the field. This paper reports attempts to mass rear two larval parasitoids of Helicoverpa spp., Heteropelma scaposum and Netelia producta. The results suggest that N. producta is the easier species to culture, although the parasitism rates for either wasp species were not high (29% for N. producta and 19% for H. scaposum). The authors suggest ways in which the parasitism rates could be increased and culturing made easier. It was found that culturing H. scaposum resulted in a male-biased sex ratio that was less suitable for mass release. Possible reasons for the bias are discussed, including single-locus complementary sex determination (CSD) that can result in a high proportion of homozygotic diploid males occurring in inbred populations. Although single-locus CSD is a plausible explanation for the male biased sex ratio, the authors caution that more work is needed to confirm that it can occur in H. scaposum.