Influence of fall armyworm Spodoptera frugiperda egg mass scales and layers on the performance of three species of egg parasitoid Trichogramma with different ovipositor lengths

Abstract

BackgroundThe fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a highly polyphagous and destructive pest of maize and other cereal crops. Biological control is a potential alternative to chemical insecticides used for the management of FAW in maize. Egg parasitoids are promising biocontrol agents as they kill the insect pest at their egg stage before it hatches, thus preventing the damaging larval stage. Trichogramma is widely used in augmentative biological control of FAW in native and invaded regions. However, FAW lay egg masses in layer by layer and eggs are covered with egg scales, this may affect the performance of Trichogramma parasitoids. Therefore, the parasitism potential of three Trichogramma species was studied on eggs with or without scales and layered eggs of FAW, further the impact of parasitoids ovipositor length on parasitism was also determined. This helps to understand the parasitism potential of parasitoids on different egg type for better implementation of biological control programs against FAW.ResultsThe effect of FAW egg mass with or without scales and layered eggs on the performance of Trichogramma chilonis, T. pretiosum and T. mwanzai was studied and results indicated that egg mass scales and the layered eggs were significantly affected the parasitism potential of Trichogramma species, but did not affect the parasitoid emergence. In general, T. chilonis parasitized a higher percentage of eggs with or without scales and layered eggs of FAW than the other two species. T. chilonis and T. mwanzai had a greater ovipositor length than T. pretiosum.ConclusionThe performance of evaluated Trichogramma species on FAW eggs with or without scales and layered eggs affected the parasitism success. The parasitism success of T. chilonis was comparably higher than other tested species. Hence, the scales on egg masses and layered eggs of FAW should be taken into account while selecting the Trichogramma species in the biological control of FAW.