Quantitative Changes in Enzymatic Titer That Offers Resistance against Emamectin Benzoate in Spodoptera litura (Fabricius) Population Collected from Vegetable Crop Ecosystem

Aims: To understand the role of detoxifying enzymes in resistance development in Spodoptera litura against emamectin benzoate Place and Duration of Study: This experiment was carried out in the laboratory of Department of Entomology and Central Instrumentation Cell, College of Agriculture, Rajendranagar during kharif, 2022 Methodology: Quantitative alterations in detoxification enzymes linked to emamectin benzoate resistance were evaluated in S. litura field populations collected from Chevella and Maheshwaram mandals and compared with a susceptible reference strain. The activities of esterase, glutathione S-transferase (GST) and cytochrome P450 monooxygenase (MFO) were measured in third-instar larvae that survived LC₅₀ exposure, using standard biochemical assay methods. Results: The activity of detoxifying enzymes in emamectin benzoate–treated F1 third instar larvae of S. litura revealed that GST and esterases were significantly higher in Chevella and Maheshwaram field populations compared to the susceptible population, while MFO activity did not differ significantly. GST showed the highest increase (2.84–2.86-fold) followed by esterases (1.63–1.74-fold), indicating their major and partial roles, respectively, in detoxification of emamectin benzoate. Correlation analysis further confirmed a strong positive relationship between GST and esterase activities with resistance ratios (R² = 0.95–0.99), whereas MFO showed negligible correlation. Overall, GST emerged as the key enzyme conferring resistance to emamectin benzoate in field populations of S. litura, with esterases contributing to a lesser extent. Conclusion: Understanding the enzymatic basis of resistance highlights the need for proper insecticide rotation and integrated pest management strategies to sustain its effectiveness.