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The toxicity of organophosphorus insecticide (profenofos), pyrethroid insecticide (esfenvalirate), insect growth regulators, (flufenoxuron) and biocide as natural products (spinosad) increased when mixed with the butylated hydroxyanisol (BHA) and ergosterol biosynthesis inhibiting (EBI) fungicides to 2nd instar larvae of Spodoptera littoralis. Present study was carried out by feeding 2nd instar larvae on castor bean leaves treated with different concentrations of profenofos, esfenvalirate, flufenoxuron and spinosad either alone or in mixtures with BHA, EBI fungicide or IGR. Interestingly, these BHA and EBI did not kill the larvae at concentration up to 100 ppm, moreover 20 ppm of each BHA or EBI fungicide with concentrations of the insecticides increased the toxicity of these insecticides. Also, all data indicated that the calculated LC50 of the insecticides alone were higher than the insecticides and BHA, EBI fungicides or IGR. For instance, the LC50 of profenofos alone was 1.90 ppm, decreased to 0.08, 0.20, 0.24 and 0.22 ppm when mixed with BHA, difenoconazol, penconazol and flufenoxuron respectivily. Also, the insecticidal action increased by 23.75, 9.5, 7.91 and 8.63 folds. The LC50 values decreased when esfenvalirate mixed with BHA, difenoconazol, penconazol and flufenoxuron reached 0.32, 0.21, 0.28 and 0.33 ppm compared with 1.58 ppm when esfenvalirate used alone. Also, the insecticidal action increased by 4.93, 7.52, 5.64 and 4.78 folds when mixed with the mentioned BHA, EBI fungicides or the IGR respectively. Concerning flufenoxuron LC50 values alone was 1.83 decreased to 0.12, 0.19 and 0.22 ppm when mixed with BHA, difenoconazol, penconazol and flufenoxuron respectively, insecticidal action increased by 15.25, 9.63 and 8.31 folds respectively. LC50 values of spinosad was 1.44 ppm when used alone, decreased to 0.21, 0.21, 0.25 and 0.20 ppm when was mixed with BHA, difenoconazol, penconazol and flufenoxuron respectively, insecticidal action was increased by 6.85, 6.85, 5.76 and 7.2 folds respectively. These results suggested that the antioxidant butylated hydroxyanisol (BHA), ergosterol biosynthesis inhibiting (EBI) fungicides and the IGRs enhanced the insecticidal activity of profenofos, esfenvalirate and spinosad against 2nd instar S. littoralis. [ABSTRACT FROM AUTHOR]