Parasitism of Ooencyrtus telenomicida on common sunn pest's eggs: effect of host age and previous parasitism by Trissolcus grandis

The parasitic wasps Ooencyrtus telenomicida and Trissolcus grandis are among the most common biocontrol agents of the common sunn pest (CSP), Eurygaster integriceps. The Ooencyrtus spp. act as facultative hyperparasitoids of CSP eggs, which may earlier have parasitized by Scelionidae. The preference and choice of these wasps among hosts of different quality (recently deposited eggs, 2-, and 4d-old eggs, as well as recently parasitized CSP eggs by T. grandis, 3-, 7-, and 10 d-old parasitized eggs) was studied. The results indicated that, unexpectedly, parasitism rate was the highest in 4d-old eggs, while the wasps significantly avoided 10d-old parasitized eggs. The functional response experiments were carried out with the same set of hosts. The 72h-old inexperienced fertile females were confined individually with different host densities for 6h. The response of the wasp to all kinds of the host was a type III response. No response to 7d-old parasitized eggs was evident (non-significant parameters). Depending on the treatment, the highest parasitism rate occurred at densities 5 to 9 which was between 25.7 and 46.5%. The handling time and maximum attack rate ranged between 0.61 - 1.83 h and 3.27-9.85 host eggs respectively. The maximim parasitism rates was observed in the 10d-old parasitized eggs, newly deposited eggs and 4d-old eggs. The results of the functional response and host preference experiments were not confirming, and therefore more studies are still required to reveal the impact of host quality on the parasitoid.