Beyond molting disruption: Tebufenozide modifies gut immunity and antiviral responses in Helicoverpa armigera (Noctuidae).

The insect growth regulator tebufenozide, an ecdysone agonist, is widely used to control Helicoverpa armigera through disrupting molting and development. However, its other effects on the insect physiology remain poorly understood. This study investigates how tebufenozide modulates gut immunity, microbial homeostasis, and antiviral defense mechanisms in H. armigera larvae. Using RT-qPCR, we analyzed the expression of key immune genes following exposure to lethal (LC₅₀) and sublethal (LC₁₀, LC₂₅) concentrations of tebufenozide. Our results demonstrate that tebufenozide induced the IMD pathway through upregulating Relish and PGRP-LC while suppressing PGRP-LB, leading to increased expression of antimicrobial peptides, Gallerimycin, Gloverin, Attacin and Defensin. Additionally, tebufenozide altered reactive oxygen species (ROS) dynamics by enhancing DUOX and SOD expression, resulted in decreased gut bacterial load. Additionally, tebufenozide enhanced antiviral defenses by upregulating RNAi pathway genes (Dicer1, Ago1, Dicer2, Ago2) and apoptosis-related genes (Caspase1, Caspase5), while downregulating the apoptosis inhibitor, Survivin. Consequently, viral titers of Helicoverpa armigera nucleopolyhedrovirus (HaNPV) were significantly lower in the treated larvae compared to the controls. These findings reveal that tebufenozide exerts immunomodulatory effects beyond molting disruption, influencing gut immunity, microbiota titer, and antiviral responses. This study highlights the broader physiological impacts of ecdysone agonists and their potential implications for integrated pest management strategies combining chemical and microbial agents.