The present study was carried out to determine the residues of the neonicotinoid insecticide imidacloprid , and the fungicide tetraconazole and their persistence in and on cucumber fruits after whitefly and powdery mildew control .The field experimental design was a complete randomized blocks design with two treatments for imidacloprid and tetraconazole in addition to control (42m 2 ).The application was carried out using knapsack sprayer equipped with one nozzle. Cucumber fruits samples were

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... llected from each replicate (one Kg) at time intervals of one hour after application( zero time), 1 , 3 , 5 , 8 , 11 , 15 and 21 days after treatment with imidacloprid and tetraconazole. Estimation of imidacloprid residues were performed by High pressure liquid chromatography equipped with diode array UV detector .Quantitative analysis of tetraconazole residues were performed by Perkin gas chromatograph (GLC), equipped with electron capture detector (ECD. Result indicated that the recovery percentage of tetraconazole and imidacloprid were 91.62 % and 117.5% respectively. The initial deposit (one hour after application) was 0.943 mg/kg. while the detected residue amounts were 0.365, 0.271, 0.226, 0.086, 0.049, 0.028 and 0.013mg/kg of imidacloprid after 1, 3, 5, 8, 11, 15 and 21days of treatment, respectively. The calculated half life (t 1/2 ) value of this insecticide was 2.2 days. On the other hand the initial deposit of tetraconazole on and in cucumber fruits was 0.1742 mg/kg The obtained residual half-life value (t 1/2 ) of tetraconazole on and in cucumber fruits was 1.4 day. Data also revealed that the first day following application is critical in the sense of sharply decrease that reach 61.29% from the initial deposit of imidacloprid on cucumber fruits, but the loss of tetraconazole at first day was 40.41% from the initial residues on cucumber fruits.