Physiological and reproductive impacts of a ternary insecticide combination (spinetoram, novaluron and broflanilide) on Spodoptera litura

Pest insects are frequently exposed to multiple insecticides in agricultural systems, yet the sublethal physiological consequences of such combined exposures remain poorly understood. This study evaluated the synergistic toxicity and physiological disruptions caused by individual insecticides, spinetoram, novaluron and broflanilide and their ternary combination in Spodoptera litura . Toxicity bioassays revealed that the ternary mixture (LC 50 = 0.32 μL/L) was approximately ninefold more toxic than spinetoram (3.0 μL/L) or novaluron (3.1 μL/L) and exhibited strong synergism (Combination Index (CI) <1). Sublethal exposure at LC 35 significantly elevated catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione (GSH) activities, along with increased lipid peroxidation (LPO), indicating oxidative stress. Midgut histopathology showed severe epithelial degeneration and nuclear disorganisation in larvae treated with the combination. Developmental and reproductive assessments revealed prolonged larval and pupal durations, reduced pupation and adult emergence and markedly decreased fecundity and hatchability in the combination treatment. Overall, sublethal mixture of insecticides with different modes of action caused pronounced physiological, histological and reproductive impairments in S. litura , highlighting the need to evaluate mixture toxicity in integrated pest management programs.