Anti-nutritional, antifeedant, growth-disrupting and insecticidal effects of four plant essential oils on Spodoptera littoralis (Lepidoptera: Noctuidae)

Essential oils of four aromatic plants, Artemisia monosperma Del., Callistemon viminals (Sol.ex Gaertn.) G. Don, Citrus aurantifolia (Christm.) Swingle and Cupressus macrocarpa Hartw. ex Gordon, were evaluated for their anti-nutritional, antifeedant, growth inhibitory and insecticidal activities against Sopdoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). The essential oils of A. monosperma and C. aurantifolia caused the highest reduction in relative growth rate (RGR) at the tested concentrations (۱۲۵, ۲۵۰, ۵۰۰, ۱۰۰۰ and ۲۰۰۰mg/l). The RGR values ranged between ۸.۶۳ and ۳.۰۵ mg/day for A. monosperma, and between ۱۰.۷۴ and ۲.۸۹ mg/day for C. aurantifolia compared with ۱۴.۸۹ mg/day for control after ۷۲ h of treatment. In general, the results showed that the values of relative growth rate (RGR) decreased with increasing the concentration of the tested oils. In addition, the tested oils significantly reduced efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) values, particularly at the higher concentrations of ۵۰۰, ۱۰۰۰ and ۲۰۰۰mg/l. On the other hand, the tested oils showed antifeedant activity against the larvae of S. littoralis with A. monosperma and C. aurantifolia oils being more active than C. viminals and C. macrocarpa oils. The tested oils showed remarkable growth inhibition effect as the growth inhibition index values were increased from ۳۷.۶۳ to ۷۹.۸۰% for A. monosperma, from ۲۱.۶۹ to ۵۲.۱۲% for C. viminals, from ۱۶.۵۵ to ۲۸.۵۹% for C. aurantifolia and from ۳۷.۶۴ to ۵۲.۳۲% for C. macrocarpa when the concentration increased from ۱۲۵ to ۲۰۰۰mg/l. Based on chitin formation ratio values, the tested essential oils induced reduction in chitin formation. A. monosperma and C. macrocarpa essential oils revealed the highest insecticidal activity on ۴th instar larvae of S. littoralis. Examination of reproductive tracts of adult females emerged from treated larvae indicated that the tested oils caused undifferentiated ovarioles.