Comparative Toxicity and Genotoxicity of Four Insecticide Classes on Spodoptera littoralis (Lepidoptera: Noctuidae)

The Egyptian cotton leafworm, Spodoptera littoralis, is a polyphagous and destructive pest worldwide, infesting many plant families, leading to significant crop losses. In this study, we have used leaf-dip and comet assays to test the toxicity and genotoxicity of four insecticides, “Lambda® 10% EC, Emafel® 4% ME, Xentari® 54% WG, and peppermint oil” on fourth-instar larvae of The Egyptian cotton leafworm. Regarding toxicity, Emafel® was the most potent, with LC₅₀ values dropping from 0.691 µg/mL on the first day to 0.199 µg/mL by the fourth day. In contrast, Xentari® worked more slowly but steadily, with LC₅₀ values decreasing from 45.713 to 4.766 µg/mL over ten days. Lambda® demonstrated moderate effectiveness, whereas peppermint oil had little impact on larval death. Transitioning to DNA damage results, the comet assay showed that Lambda® caused the most DNA damage, followed by the Egyptian cotton leafworm. Notably, peppermint oil caused very little DNA damage, even though it contains dl-menthol and l-menthone, as found by GC-MS. In conclusion, Emafel offers rapid control but with significant genotoxicity, while Xentari provides effective, environmentally safer pest management. Peppermint oil, despite its lower toxicity, presents minimal genotoxic risk and potential for integrated pest management applications.