Effects of gamma radiation on suitability of stored cereal pest eggs and the reproductive capability of the egg parasitoid Trichogramma evanescens (Trichogrammatidae: Hymenoptera)

Abstract

A study was conducted to determine parasitization suitability and preference of irradiated and untreated eggs of the Mediterranean flour moth (MFM), Ephestia kuehniella Zeller, and the Angoumois grain moth (AGM), Sitotroga cerealella (Olivier) for mass-production and augmentative releases of T. evanescens Westwood in cereal storage and processing facilities. Eggs of both species irradiated with 200 Gy could be effectively used for propagation of T. evanescens in the sterilized host eggs. The irradiated host eggs of E. kuehniella were markedly preferred over eggs of S. cerealella. A dose of 200 and 150 Gy prevented adult emergence of E. kuehniella and S. cerealella, respectively. Treatment of immature stages of the parasitoid inside the host eggs or treatment of adults of T. evanescens with low-level doses (ranging between 0 and 140 Gy) resulted in significant reduction in the number of parasitized eggs, adult emergence and progeny production (F1) as radiation dose increased. Our study showed that MFM and AGM eggs killed by gamma radiation could be used for the rearing and release of T. evanescens into commodity storages without any risk of increasing the pest population.