The Relative Potency of some Pesticides against Cotton Leafworm, Spodoptera littoralis (Boisd.) and their Side Effect on the Natural Enemy, Chrysoperla carnea (Stephens)

The cotton leafworm, Spodoptera littoralis (Boisd.) is one of the dangerous economic insects on different crops in Egypt because it causes more damages in crops especially cotton and leafy vegetables. On the other hand, the natural enemy, Chrysoperla carnea (Stephens) is an important predator in all fields because it is able to control many insect pests and mites. In this study, six commercial pesticides (Chlorpyrifos, Alpha-cypermethrin, Methomyl, Abamectin, Biossiana, and Dipel) and two new compounds under the study (Crude extract of Beauveria bassiana metabolites and synthesis compound from Cyanoacetamide derivatives) were tested to determine their toxicity against the 2^nd instar larvae of S. littoralis and their side effects against the 2^nd instar larvae of C. carnea. All tested compounds had different degrees of toxicity against both tested insects. Based on the values of LC₅₀ , toxicity index and relative potency, Alpha-cypermethrin was the highest toxic pesticide against S. littoralis and C. carnea followed by Methomyl and Chlorpyrifos but Biossiana was the least toxic one. In addition, the toxicity of tested chemical pesticides against C. carnea was more than their toxicity against S. littoralis. While, the toxicity of tested biopesticides against C. carnea was less than their toxicity against S. littoralis. In general, the sensitivity of the predator C. carnea to the tested biopesticides was less in comparison with chemical pesticides. Therefore, this study recommends using biopesticides besides the slight using of chemical pesticides to preserve the natural enemies and environment and achieve the best pest control.