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 Cupressusmacrocarpa 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 (125, 250, 500, 1000 and 2000mg/l). The RGR values ranged between 8.63 and 3.05 mg/day for A. monosperma, and between 10.74 and 2.89 mg/day for C. aurantifolia compared with 14.89 mg/day for control after 72 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 500, 1000 and 2000mg/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 37.63 to 79.80% for A. monosperma, from 21.69 to 52.12% for C. viminals, from 16.55 to 28.59% for C. aurantifolia and from 37.64 to 52.32% for C. macrocarpa when the concentration increased from 125 to 2000mg/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 4^th instar larvae of S. littoralis. Examination of reproductive tracts of adult females emerged from treated larvae indicated that the tested oils caused undifferentiated ovarioles.