The work was conducted to clarify the efficiency of certain insecticides on the population of whitefly B. tabaci and incidence of yellow leaf curl virus (TYLCV) in tomato field. The experiment was carried out during Nili plantation of two successive seasons at El-Fayoum governorate. The obtained data showed that the alternate use of etofenprox /thiamethoxam; imidacloprid/ thiamethoxam; acetamiprid/ etofenprox; single continuous application of etofenprox; etofenprox / imidacloprid; acetamiprid/ imidacloprid; thiamethoxam/ acetamiprid; imidacloprid; thiamethoxam and acetamiprid gave excellent initial mortality over 90% on the adult stage of B. tabaci and incidence of tomato yellow leaf curl virus without significant differences between treatments. Thimethoxam as soil drench proved to be the most effective insecticide against adult and immature stages of whitefly, while acetamiprid achieved the lowest mortality for these two stages as well as short residual mortality. On the other hand, alternation of etofenprox / imidacloprid showed the highest initial mortality on nymphs. Residue levels in tomato fruits were also investigated at 30, 45 and 60 days after application of tested insecticides. For imidacloprid residues were found in amounts nearly above maximum residue levels MRLs 30 days while degraded to amounts below MRL by the progression of time to 45 and 60 days after application. Application of imidacloprid in alternate spray program with thiamethoxam; etofenprox; acetamiprid resulted in residues below MRL at the 3 preharvest intervals. Acetamiprid when used at the recommended rate showed the residue of 0.36 mg/kg at early season and then decreased to 0.08 mg/kg at late season. Alternate use of acetamiprid with thiamethoxam; etofenprox or imidacloprid reduce MRLs in tomato fruits. The successive applications of etofenprox alone at the recommended rate resulted in residues above MRL after 30 and 45 days and approximately near MRL at 60 days. On the other hand, the half rate in alternative use with imidacloprid; acetamiprid or thiamethoxam showed residues below MRL at all sampling intervals. Thiamethoxam when used in single successive applications gave residues of 2.5, 1.9 and 1.5 mg/kg at the 3 preharvest intervals, respectively

Field trials were conducted at El-Gharbia governorate to determine the insecticidal activities of chlorpyrifos-methyl, profenofos and methomyl on tomato plants against the cotton leaf-worm (Spodotera littoralis). Data showed the high initial mortality (100, 100 and 100%) against the second and the fourth instars larvae with reasonable persistence. The residues of these insecticides on fruits of the sprayed and contaminated tomato plants were determined by GLC and HPLC, with recoveries of 100, 100 and 94.58%, respectively. The initial deposits of chlorpyrifos-methyl, profenofos and methomyl were 2.10, 2.58 and 20.11ppm, while decreased to 0.19, 1.41 and 0.33ppm after 3,1 and 13 days from spraying, respectively, such residue levels are below the maximum residue level (MRL). The estimated half-life values (t0.5) were 0.4898, 1.026 and 1.1867 days for the same insecticides, respectively