Factors affecting reproductive success and life history parameters of Bracon hebetor Say (Hymenoptera: Braconidae) from three host-associated populations

Abstract

Augmentative releases of native natural enemies are viable strategies for suppression of crop pests. Successful implementation of this approach requires in-depth knowledge of the natural enemy, its host(s), and the agroecosystem. In particular, appropriate mass rearing and release strategies rely on a thorough understanding of the reproductive biology of the natural enemy. In the present study, we evaluated the effects of parasitoid source (host habitat origin), fruit condition (i.e., ease of host access for parasitoid), impact of using an alternative host for rearing, and winter-simulated cold storage of hosts on the reproductive performance of Bracon hebetor. Several life history parameters, including attack behavior, proportion of paralyzed hosts, parasitism, oviposition, offspring sex ratio, and life table parameters were measured. Wasps originating from a pomegranate orchard-Ectomyelois ceratoniae host habitat generally had greater reproductive performance than those sourced from stored dry fruit-Plodia interpunctella or tomato field-Helicoverpa armigera habitats. Hosts infesting intact pomegranate fruit suffered greater levels of attack (e.g., paralysis, parasitism, and oviposition) than did more accessible hosts infesting damaged fruit. However, offspring sex ratio was generally more female-biased in the damaged fruit treatments. The developmental period of B. hebetor larvae and pupae was shorter (mean generation time) on Ephestia kuehniella hosts that had been subjected to a 2-month cold storage period (winter simulation) than untreated control hosts not subjected to cold storage. Sex ratio of offspring did not differ significantly between the treatments. Our studies demonstrated differential effects of wasp population source, and other biotic factors, on the reproductive biology of B. hebetor. Our current understanding suggests that efficacious protection of pomegranate crops with B. hebetor might be accomplished by using a rearing protocol that incorporates parasitoids originating from a pomegranate-E. ceratoniae source, followed by rearing on cold-treated E. kuehniella prior to release. Development of optimal release strategies is a topic for future studies.