LETHAL EFFECTS OF SPINOSAD AND AZADIRACHTIN ON THE COTTON LEAFWORM, SPODOPTERA LITTORALlS (BOISD.) (LEPIDOPTERA: NOCTUIDAE)

Laboratory experiments have been conducted to determine the lethal effects of Spinosad and Azadirachtin on the cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) larvae by a diet incorporation bioassay. Newly molted third instar larvae were exposed through ingestion to different concentrations. Larval mortality of S. littoralis increased with the concentration resulting a LC 50 values of 1.38 (ig/ml and 0.14 Hg/rhl for Spinosad and Azadirachtin respectively, the Mortality times decreased with the concentration Increase. Sublethal effects were studied by treating of third instar larvae with a concentration equivalent to the respective LC 50. Both insecticides significantly increased larval development period from treatment until pupation, but the effect of Azadirachtin was greater than Spinosad. The pupation period was significantly prolonged in male pupae when the larvae were treated with Spinosad, whereas With Azadirachtin this effect happened in both sexes. Egg viability was reduced with Azadirachtin, and the oviposition period was affected by Spinosad. No significant differences were found in pre-oviposition periods, spermatophore number, fecundity and adult longevity.