Environmental and maternal effects on host selection and parasitism success of Bracon hebetor

The biological control programs supporting the native species of natural enemies are far more sustainable than those which use exotic enemies of the target pest. Little is known about the effects of the surrounding environment on host selection behavior of Bracon hebetor Say (Hymenoptera: Braconidae). In the present study, the effects of the origin of the parasitoid populations, host species and parasitoid rearing history on host selection and parasitism success of B. hebetor were investigated. Several life-history parameters, including the frequency of parasitism, percentage parasitism, egg load, survival rate and the offspring sex ratio of the parasitoid were measured. In terms of both selection and parasitism success, B. hebetor preferred Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) over Apomyelois ceratoniae Zeller (Lepidoptera: Pyralidae) and Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), and A. ceratoniae over H. armigera. When different populations of B. hebetor were compared, the B. hebetor population originated from orchard was the most successful compared with the field and store populations. In addition, the rearing history was influential on the parasitism preference and success: a better performance of the parasitoid was obtained when it was reared on its original host compared with an intermediate host, E. kuehniella. The causes and consequences of these findings were further discussed in relation with mass rearing of this parasitoid for biological control programs.