Biochemical Disruption and Lethal Effects of Lufenuron and Hexaflumuron on the Cotton Leafworm (Spodoptera littoralis...

<b>Background and Objective:</b> The Egyptian cotton leafworm, scientifically named <i>Spodoptera littoralis</i>, is a major economically important pest that causes extensive economic losses across Africa, particularly in Egypt. The current study aimed to estimate the effects of lufenuron and hexaflumuron on the survival potential, development, metamorphosis and main metabolites of this economically important insect pest. <b>Materials and Methods:</b> Penultimate instar larvae were treated with four concentrations (250, 500, 1000 and 2000 ppm) of lufenuron and hexaflumuron using a leaf-dipping technique on fresh castor bean leaves. Mortality, development time, pupation and metabolite contents were monitored across early-, mid- and late-aged larvae. Major metabolites (proteins, carbohydrates and lipids) were analyzed using standard biochemical assays. Statistical analysis was performed to determine concentration-dependent effects and significance was evaluated at the appropriate confidence level. <b>Results:</b> The obtained results revealed that treatment with the highest concentration resulted in complete larval mortality for both compounds. Other concentrations recorded a concentration-dependent increase in larval mortality, with severe mortality observed during the early days after treatment. Both lufenuron and hexaflumuron induced pronounced negative effects on larval growth and developmental rates, regardless of the concentration level or the targeted larval age. Pupation percentages were also affected; higher concentrations induced complete pupation failure. A disturbance in the main body metabolites of the penultimate instar larvae was also recorded across early-, mid- and late-aged larvae. The total main metabolite content was drastically disrupted, regardless of the tested compound or the larval period. <b>Conclusion:</b> Lufenuron and hexaflumuron have a potent effect in curbing the cotton leafworm, <i>S. littoralis</i> and a strong effect on disrupting its vital and physiological processes.