Tomato is an economically important vegetable crop which is attacked heavily by insect pests leading to reduction of yield and quality of the fruits. Field experiments were carried out to investigate the dissipation of methomyl (a common insecticide) used mainly on tomato fruits. LC-MS/MS coupled with the QuEChERS method were used for the determination of methomyl. The results showed that the recovery using matrix-matched standards ranged from 87.8 to 101.3%, with relative standard deviation of 2.5 to 7.5%. Kinetics equation, Log R = log R0 – 0.434 Kt, was used to calculate the rate of degradation in tomato, soil and water. Residue half-life calculated using kinetic rate ranged from 1.95 to 1.63 days in tomato and soil, respectively. From the results it was concluded that tomato fruits can be safely harvested for consumption after 15 days of application based on estimated preharvest interval (PHI). It is advisable to re-estimate the PHI regularly owing to data from the EU and Codex.

The normal formulation of etofenprox was developed to nanoformulation and used against the adults of silver whitefly, Bemisia tabaci in eggplant fields. Three concentrations of both the normal and nanoformulations were used. The concentrations of etofenprox nanoformulation were one-fifth of the normal formulation. The nanosize of etofenprox ranged from 225 to 489 nm. The loading capacity of etofenprox was 60.7 ± 5.7%. The obtained results showed that the LC ₅₀ of the normal formulation was four times more than the nanoformulation. The LC ₅₀ for the nanoformulation was 0.9 and 3.5 ppm for the normal formulation of etofenprox. This means that the nanoformulation of etofenprox was more effective than the normal. The residues of both nano and normal formulations were determined in eggplant fruits after three applications. The obtained results showed that the residue of nanoformulation after 1 hour of treatment was 0.51 ± 0.03 compared with 0.62 ± 0.03 mg · kg ^–1 ± SD in normal formulation. After 1 hour of treatment the residue of etofenprox was reduced to 0.11 ± 0.1 and 0.22 ± 0.02 mg · kg ^–1 ± SD in nano and normal formulations, respectively. The dissipation rates of both nano and normal formulations after 1 hour were 78.3 and 64.5%, respectively. The degradation rate (K) in nanoformulation and normal etofenprox was 1.33 and 0.73 mg · kg ^–1 ± SD, respectively. The residue half-life (LR ₅₀) was 0.52 and 1 day, respectively. The preharvest interval (PHI) was 6 days for both nano and normal etofenprox formulations. The results confirmed that nanoetofenprox was more effective against B. tabaci adults, with lower persistence and lower residue than the normal formulation of etofenprox.