Dissipation pattern of dimethoate on chilli in polyhouse and open field

Dimethoate is a systemic organophosphorous insecticide, applied on chilli to control sap sucking insects, thrips and mites in India. Use of dimethoate in poly house and open fields is very common. As per the ICAR recent suggestions dimethoate 30%EC was applied twice @300g a.i. ha-1, first spray at fruit initiation followed by second spray at 10 days interval as per the farmers practice to compare the dissipation dynamics of pesticide residues in open field and poly house situations so as to suggest PHIs for addressing the food safety issues. Dimethoateresidues were quantified through regular sampling till the residues fell below determination level (BDL) of 0.05 mg kg-1 following the validated QuEChERS method. The qualitative and quantitative analysis of dimethoate was performed on GC-FPD and GC-MSMS (TQD). Initial deposits of2.42 mg kg-1 detected in chilli samples collected from poly house, dissipated to BDL by 10th day with a half-life of 2.61 days. In open fields, deposits of 0.19 mg kg-1 dissipated to BDL by 7th day with half-life of 36.47 days, indicating that dissipation is slow in poly house compared to open fields due to various factors. There are no maximum residue limit for dimethoate in chilli as per Codex Alimentarius Commission (CAC) and hence based on the present study Dimethoate initial deposits (0.19 mg kg-1) are less than FSSAI MRL of 2 mg kg-1, hence a PHI of 1 day can be recommended. In case of poly house, initial deposit of 2.42 mg kg-1 was observed and hence a safe waiting period of 7 days can be recommended since FSSAI MRL is 2 mg kg-1 for food safety.