Tropentag, September 10 - 12, 2025, Bonn "Reconciling land system changes with planetary health"

Host‑instar selection, interspecific competition, and reproductive capacity of extant and novel Hymenoptera: Braconidae on Egyptian cotton leafworm

¹Alexandria University, Applied Entomology, Egypt
²Plant protection research institute, Biological Control, Egypt

Abstract

Cotesia marginiventris (Cresson) and Microplitis rufiventris Kok. (Hymenoptera: Braconidae) are larval endoparasitoids of Spodoptera frugiperda (Smith) and S. littoralis (Boisd.), respectively. Cotesia marginiventris was introduced in Egypt to control the recent invasive pest, S. frugiperda and local one, S. littoralis. Therefore, competition between the two parasitoid species may occur. When single females of C. marginiventris (Exp. 1), single females of M. rufiventris (Exp. 2), and one female each
of C. marginiventris and M. rufiventris (Exp. 3) were offered a choice of 60 1^st, 60 2nd, and 60 3rd instars, of the tested host species, S. littoralis and different parasitisation levels were obtained. In the non-competitive context (Exps. 1, 2), all instars were parasitized, but C. marginiventris and M. rufiventris parasitised primarily 2nd and 3rd instar host larvae, respectively. In the competitive context (Exp. 3), the same preference pattern emerged but the percentage of parasitism was lower than in each of the two non-competitive contexts. M. rufiventris appears to be a superior competitor when simultaneously exploiting the host with the other parasitoid species. The knowledge of this work can be used to predict and/or understand possible outcomes of a biological control programme using the two biocontrol agents against one or the two pests species, and to gain insight into possible biotic interference between species at the same trophic level exploiting the same host.The knowledge generated from this work may increase our knowledge on performance of a new biocontrol agent in Egypt if released with the extant parasitoid Microplitis rufiventris. If the study was conducted with S. frugiperda, probably that C. marginiventris would be the winner for that pest as they origin from the same area. We don’t know how the 2 parasitoids will interact with S. frugiperda and S. littoralis in the field as this study is limited to S. littoralis, due to strictly quarantine measures for S. frugiperda.

Keywords: Cotesia marginiventris, instar preference, interspecific interaction, Microplitis rufiventris, Spodoptera littoralis

Contact Address: Esmat M. Hegazi, Alexandria University, Applied Entomology, 50 sokina bent El hussien, 21545 Alexandria, Egypt, e-mail: eshegazihotmail.com