Antifeedant and toxic activity of some plant extracts, chemical and bio insecticides against the cotton leafworm, Spodoptera littoralis (Boisd.)

The effect of three different compounds, namely protecto (bioinsecticide based on Bacillus thuringienses), coumarin (plant extract of Chicory flower) and Neemix (plant extract of Azadirachta indica) were assayed on the 4 th larval instar of cotton leafworm Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae). All tested compounds exhibited a significant antifeedant activity, coumarin recorded the highest mean of antifeedant activity reached (89.19) followed by azadirachtin (81.7) at 100 x 10 3 µg/ml and protecto (32.01) at 200 x 10 3 µg/ml. The overall larval mortality after treatment with lannate, protecto, coumarin and azadirachtin ranged between (48.3 – 70.0%), (20.0 – 50.0%), (25.0 – 60.0%) and (21.6 – 55.0%), respectively. Coumarin and azadirachtin concentrations exhibited longer larval duration, while protecto gave a slight difference in the total larval period. All tested concentrations of all compounds led to significant prolongation in pupal stage duration. Percentage of adult emergence increased with decreasing the tested concentrations of the tested compounds, the percentage ranged between (73.3 – 89.5%), (52.4 – 94.8%) and (66.6 – 93.1%) after treatment with protecto, coumarin and azadirachtin, respectively. The average number of males was higher than that of females after larval treatments with protecto, coumarin and azadirachtin. Adult and pupal deformation percentage increased with increasing concentration of tested compounds. Number of eggs/female and hatchability % decreased with increasing concentrations of tested compounds. Female sterility percentage increased by increasing concentrations of tested compounds.