Host-Specificity and Parasitism Rate of Trichogramma brassicae (Hymenoptera: Trichogrammatidae) on Eggs of Ostrinia nubilalis

Abstract

Egg parasitoids belonging to the genus Trichogramma are widely used as biological control agents against lepidopteran pests in agricultural ecosystems. The present study evaluated the host-specificity and parasitism rate of Trichogramma brassicae (Hymenoptera: Trichogrammatidae) on eggs of Ostrinia nubilalis under controlled laboratory conditions. Freshly laid eggs of O. nubilalis were exposed to adult parasitoids at different host densities to assess parasitism efficiency, host acceptance, developmental success, and emergence rate of the parasitoid. Behavioral observations were conducted to determine host recognition and oviposition preference. The results demonstrated that T. brassicae effectively parasitized eggs of O. nubilalis, with parasitism rates varying according to host density and environmental conditions. Higher parasitism efficiency was observed at moderate host densities, indicating optimal host utilization by the parasitoid. Developmental duration, adult emergence, and progeny production were significantly influenced by host egg quality and availability. The parasitoid exhibited strong host specificity toward O. nubilalis eggs, suggesting its suitability as a targeted biological control agent against this economically important pest. Temperature and humidity conditions also affected parasitoid activity, survival, and reproductive performance. Successful development of parasitoid offspring within host eggs resulted in reduced pest emergence and suppression of pest population growth. The findings highlight the potential application of T. brassicae in integrated pest management programs aimed at controlling O. nubilalis infestations in crop production systems. This study contributes valuable information for optimizing mass-rearing techniques and field release strategies of egg parasitoids for sustainable biological pest control.