Persistence and effect of processing on chlorpyriphos residues in tomato (Lycopersicon esculantum Mill.)

• T1/2 of chlorpyriphos in tomato was 4.43 and 4.38 days when applied @ 400 and 800 g a.i. ha−1
• Residues were below MRL of 0.05 mg kg−1 in both the doses on 0 day.
• Residues could be reduced by 91 percent by washing followed by boiling and 64 percent by peeling
• Residues in soil were not in detectable level after 5th and 10th day of application.

Persistence of chlorpyriphos in tomato was studied following applications of Action 505EC at 800 and 1600 g ha−1 with active application of chlorpyriphos as 400 and 800 g a.i. ha−1. The average initial deposits of chlorpyriphos were 0.155 and 0.372 mg kg−1 on tomato fruits on application of ready-mix formulation, Action 505EC at single and double dose, respectively. The residues dissipated with half- life period of 4.43 days at single dose and 4.38 days at double dose following pseudo first order kinetics.Residues of chlorpyriphos in both the doses on 0 day were below maximum residue limit (MRL) of 0.5 mg kg−1. Processing was found very effective in reducing the residues of chlorpyriphos in tomato fruits. By washing, reduction of chlorpyriphos was in the range of 41–44 per cent. Washing followed by boiling reduced the residues from 89 to 91% whereas peeling removed residues from 62 to 64%. In soil samples, residues of chlorpyriphos reached below detectable level of 0.010 mg kg−1after 5 and 10 days after spray at single and double dose, respectively.