Competitive asymmetry between Telenomus remus and Trichogramma pretiosum (Hymenoptera: Scelionidae, Trichogrammatidae) persists under sequential parasitism of fall armyworm

Abstract Interspecific competition among parasitoids is often expected to favor the first attacker through priority effects; however, competitive outcomes may instead reflect contrasting mechanisms of intrinsic suppression and patch exploitation. We evaluated sequential competitive interactions between 2 key egg parasitoids of fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), Trichogramma pretiosum Riley and Telenomus remus Nixon, across host egg patches of 10, 50, and 100 eggs. Egg batches were exposed sequentially to reciprocal oviposition orders (Telenomus → Trichogramma; Trichogramma → Telenomus), alongside single-species controls, and offspring emergence, developmental time, and sex ratio were quantified. Multiparasitism occurred under all sequences and egg densities. At low host availability (10 eggs), Tr. pretiosum consistently outcompeted T. remus regardless of oviposition order. A supplementary 24 h interval assay at 10 eggs showed that extending the interval did not alter competitive outcomes: emergence was comparable when T. remus oviposited first, whereas Tr. pretiosum prevailed when it oviposited first. At higher host availability, T. remus increasingly dominated, whereas sequence effects were most evident at intermediate density. Developmental time varied with sequence and host context, whereas sex allocation was primarily influenced by host density. Overall, competition between T. remus and Tr. pretiosum depends on host egg density, with intrinsic competitive ability dominating at low densities and patch exploitation becoming more important at higher densities.