Spodoptera littoralis (Lepidoptera: Noctuidae) known as the African Cotton Leaf worm or Egyptian Cotton Leaf worm is one of the most common pests of cotton in the region of Adena, Turkey. The aim of this study was to determine the effects of a synthetic pyrethroid (Gamma-cyhalothrin) and neonicotinoids (Imidacloprid) on the pest to find out the resistance inducing process during several generations. Induced resistance to gamma-cyhalothrin up to 12 generations and to Imidacloprid for 7

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... s was studied by assessing the resistance ratio (RR) of LC 50 and LC 90 with confidence limit of %95. The resistance ratios (RR) for LC 50 and LC 90 of gamma-cyhalothrin were calculated 16.85 and 18.82 and for Imidacloprid were 9.76 and 8.68, respectively. In order to study the effect of synergists on the insecticides, three different synergists including S, S, S-tributilfosforotritioat (DEF), piperonyl butoxide (PBO) and diethyl maleate (DEM) were used and compared the Synergism Ratio (SR) with control. The highest SR for both insecticides belonged to application of DEM synergist. It is concluded that DEM could be recommended to be applied with Gamma-cyhalothrin and Imidacloprid to prevent or postpone the resistance induction into S .littoralis .