Host preference and hyperparasitism of Ooencyrtus fecundus Ferriere & Voegele (Hym. Encyrtidae) egg parasitoid of sunn pest and hyperparasitoid of Trissolcus spp.

Among biological control agents of common sunn pest (CSP), Eurygaster integriceps Puton, egg parasitoids of family Encyrtidae have little been studied. The Encyrtidae can play different roles in a cereal agroecosystem depending on level which it will occupy in food chain. It means it can appear either as primary parasitoid of CSP or hyperparasitoid of the platygastrids. Although at first glance hyperparasitism seems an undesirable property, but it depends mainly on preference of the parasitoid. If parasitoid prefer unparasitized hosts, may enhance control level. In this study, host preference of Ooencyrtus fecundus Ferriere & Voegele (Hym.: Encyrtidae) was evaluated in pairwise experiments between three kinds of hosts (fresh host eggs, 6d-old host eggs and eggs parasitized by Trissolcus grandis (Thomson) (Hym.: Platygastridae) (8d-old)). The results revealed that the parasitoid definitely prefer the fresh eggs and the preference is not affected by relative densities of the hosts. When no suitable host was available, handling was declined considerably and negative effect of fetal development was stronger than previous parasitism. It seems that the wasp partly saves its reproductive energy for subsequent fortunes in circumstances that the favorable host is unavailable.