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

The insecticide malathion (57% E.C.) was applied at the rate of 712.5 gm active ingredient per feddan on dill, Anethum graveolens L. and coriander, Corianderum sativum L. for controlling aphids infesting these plants. An analytical method, using gas chromatography equipped with flame photometric detector was used for detecting the insecticide residues. A field trial was conducted to determine the rate of dissipation of malathion in dill and coriander plants and in the resulting oil. Residue analysis showed that the initial deposits determined one hour after application were 35.81 & 22.7 ppm in dill and coriander plants, respectively. Rates of dissipation of malathion were 4.72, 51.1, 68.39, 88.41 and 93.49% in dill plants and were 13.61, 43.22, 66.78, 86.26 and 91.85% in coriander plants at 1, 3, 7, 14 and 21 days post treatment, respectively. The pesticide was decayed quite rapidly in and on dill and coriander plants and detectable residues (1.62 and 0.93 ppm) were observed in these plants 28 days after treatment. At harvest 46 days for coriander and 70 days for dill after application malathion was found at average levels of 0.78 mg/kg and 0.54 mg/kg in dill and coriander dry seed, respectively. The volatile oil extracted from the seed by steam distillation process was contaminated with the insecticide at a higher levels than in the seed [about sevenfold in dill oil, 5.21 mg/kg and ninteenfold in coriander oil 10.16 mg/kg]. This means that malathion had tendency to co-distill with the dill and coriander oil throughout steam distillation process.

Flusilazole and triflumizole residues in apple fruits were chemically determined at different periods after spraying of these fungicides under field conditions. The obtained results indicated that, seven days after flusilazole application, unwashed apple fruits were found contained higher residues (0.322 ppm) than the allowed tolerance level (0.2 ppm), while washed and peeled fruits were contained lower residues (0.149 and 0.087 ppm, respectively) after the same period from experiment. These residues were rapidly decreased by elapse of time, so unwashed, washed and peeled apple fruits were contained levels below the allowed MRL i.e. 0.092, 0.008 and <0 ppm, respectively after fourteen days of flusilazole application Accordingly, unwashed apple fruits could be marketed safely 14 days after flusilazole application, while washed and peeled fruits could be used safely after seven days. In the case of triflumizole, unwashed apple fruits were contained 2.030 ppm after five days of application. Such residue is higher than the tolerance value (2.0 ppm), while washed and peeled fruits were contained residues below the tolerance permissive values i.e. 1.010 and 1.970 ppm after three and one days of application, respectively. These values were rapidly decreased by time prolongation, so, unwashed, washed, and peeled apple fruits were contained residues below the allowed tolerance of 1.280, 0.490 and 0.160 ppm at seven days after triflumizole application, respectively. Accordingly, unwashed apple fruits could be marketed safely seven days after triflumizole application, while washed and peeled fruits could used safely three and one days after application, 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