TOXICOLOGICAL AND BIOLOGICAL EFFECTS OF SOME INSECTICIDES ON THE COTTON LEAFWORM, Spodoptra littorallis (Boisd.).

Toxicity of five insecticides belonging to different groups of chemicals, namely: chlorpyrifos, methomyl, emamectin benzoate, protecto and biovar to cotton leafworm were evaluated under the field and laboratory conditions. The effect of the tested chemicals on some biological aspects of 2nd and 4th instar larvae of the cotton leafworm, Spodoptra littoralis (Boisd.) were investigated. The lethal concentrate (LC50 and LC90) values were calculated after 24, 48, and 72 hr., post-treatment. The obtained results showed that there was a wide range of toxicity of the tested pesticides; however the insecticide bestban showed to be the highest toxic compound effect against 2nd and 4th instar larvae, with LC50 and LC90 values after 72 hr., post-treatment recording 0.05, 0.22 mg/l and 0.15, 1.10 mg/l for 2nd and 4th instar larvae, respectively. On the other hand, the biopesticide biovar exhibited the lowest toxicity to the tested larvae at both levels of toxicity (LC50; LC90 values after 72 hr., recording 414; 856 mg/l and 1100; 1740 mg/l) for 2nd and 4th instar larvae, respectively. The other tested insecticides occupied an intermediate position between the highest and the lowest toxic pesticides. Regarding the biological effects, results showed that, the tested insecticides induced a clear reduction in mean larval weight and mean pupal weight compared with the control. The tested insecticides affected the larval duration, pupal duration, pupation, adult emergence and adult longevity. [ABSTRACT FROM AUTHOR]