Chemical Profiling and Bioactivities of Pelargonium graveolens Essential Oil against Spodoptera littoralis (Lepidoptera: Noctuidae)

Scientists are searching for safer substitutes for several hazardous chemicals because of environmental concerns and the development of arthropod resistance to synthetic pesticides. Essential oils pose fewer risks to the environment and human health and are potential alternatives for crop protection; therefore, this study assessed the toxicity and biochemical activity of essential oils from geranium (Pelargonium graveolens L’Hérit) against larvae of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). In addition, molecular docking was used to determine the binding pattern of the detoxifying enzymes glutathione S-transferase (GST), cytochrome P450, and α-esterase with citronellol, the main ingredient (20.91%) of the P. graveolens extract. Concentration–mortality response assays determined lethal concentrations (LCs) of the essential oil as LC15 = 608.52 mg/L and LC50 = 1,820.77 mg/L against second-instar larvae. Additional sublethal studies showed that, compared with the control, exposure of the second-instar larvae with LC15 or LC50 levels of P. graveolens essential oil significantly increased the duration of the larval and pupal stages. Considerable biochemical alterations were found in relation to P. graveolens essential oil biochemical impact on S. littoralis larvae. According to the activity of detoxifying enzymes and the results of the molecular docking study, the citronellol molecule of P. graveolens essential oil exhibited a binding affinity of GST > cytochrome P450 > α-esterase, with an energy score of −5.346, −5.295, and −5.4278 kcal/mol, respectively. The findings confirm the potential of using essential oils in sustainable pest management.