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

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(-1) after 5 and 10 days after spray at single and double dose, respectively.