When Parasitoids Make Mistakes: Impacts of Stinging Non-Permissive Hosts

Major GoalThe overarching goal of this project is to uncover a previously unrecognized dimension of host-parasitoid trophic networks by investigating the ecological and physiological consequences when specialist parasitoids sting non-permissive hosts--caterpillars in which the parasitoid offspring cannot successfully develop. While often dismissed as 'mistakes,' this project posits that these interactions significantly alter the dynamics of ecological networks2. The research aims to demonstrate how these interactions influence the fitness of agricultural pests, provide potential reproductive or nutritional benefits to parasitoids, and modulate plant defense mechanisms. Ultimately, this work seeks to fill a critical gap in understanding complex ecological interactions and inform biologically based pest management strategies for economically significant pests such asSpodoptera frugiperda(fall armyworm) andHelicoverpa zea(corn earworm).Project ObjectivesDetermine the breadth of non-permissive hosts for several specialist parasitoids5.This objective utilizes both laboratory and field assays to identify which non-permissive host species are attacked by specialist parasitoids6. It involves testing parasitoid preferences via Y-tube olfactometer assays and confirming if parasitoid polydnaviruses (PDVs) are expressed in non-permissive hosts following an attack. Field experiments will further assess parasitoid foraging and preference in natural environments containing both permissive and non-permissive hosts.Determine the impact of stinging non-permissive hosts on parasitoid fitness.This objective investigates why specialist parasitoids attack unsuitable hosts by testing three specific hypotheses:Reproductive Benefit Hypothesis:Assessing if oviposition in non-permissive hosts prevents egg resorption and ensures continuous egg production.Nutritional Benefit Hypothesis:Determining if parasitoids obtain nutritional benefits (such as protein and lipids) by feeding on the hemolymph of non-permissive hosts.Interspecific Competitive Benefit Hypothesis:Investigating if stinging a host immunocompromised by another parasitoid species allows a specialist to successfully develop in a normally non-permissive host.Quantify the impact of parasitoids on the fitness of non-permissive hosts.This objective measures the non-reproductive effects of parasitoid attacks on host performance, including larval duration, pupation rate, adult eclosion rate, and survival. It further examines the physiological mechanisms driving these effects, such as the impact of parasitoid venom and viruses on the host's immune system, microbiome, and potential changes in behavioral aggression.Investigate how parasitoids can alter the ability of non-permissive hosts to induce plant defenses.This objective analyzes how parasitoid attacks modify caterpillar oral secretions (specifically the downregulation of glucose oxidase) and how these changes influence the elicitation of defensive responses in host plants. The study will assay plant defense proteins (e.g., trypsin inhibitor) and conduct proteomic analyses of saliva to understand how parasitism mediates plant-herbivore interactions.