Insights into the toxicity, enzyme activity, and molecular docking of chemical and bio-insecticides against the fall armyworm, <i>Spodoptera frugiperda</i>

The fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is a major global pest that threatens cereal crops. Insecticides remain one of the key strategies for its management. This study assessed the toxicity, developmental effects, detoxification enzyme activity, and molecular docking interactions of 2 chemical insecticides profenophos (organophosphates group) and cypermethrin (pyrethroids group) and 2 bio-insecticides (spinosad and Bacillus thuringiensis) on S. frugiperda. Bioassay results revealed that spinosad exhibited the highest toxicity, followed by cypermethrin, profenophos, and B. thuringiensis against second-instar larvae. Exposure to cypermethrin at the estimated LC50 value significantly prolonged larval duration, while all treatments increased pupal duration. However, none of the treatments affected other biological parameters, including pupal weight, pupation rate, and adult emergence. Enzymatic analysis demonstrated significant alterations in the activities of acetylcholinesterase (AChE) and detoxification enzymes (α-esterase, cytochrome P450, and glutathione S-transferase [GST]) following exposure to lethal concentrations of the insecticides. Molecular docking analysis further indicated that spinosad exhibited the strongest binding affinity to α-esterase and cytochrome P450, whereas cypermethrin displayed the highest affinity for AChE. In contrast, profenophos showed the weakest binding interactions across all enzyme targets. These findings provide insights into the efficacy and biochemical interactions of chemical and bio-insecticides, offering valuable information for the targeted management of S. frugiperda.