PERSISTENCE OF SOME ORGANOPHOSPHOROUS INSECTICIDES IN ORANGE FRUIT

The persistence of seven organophosphorous insecticides (chlorpyrifos-methyl, dimethoate, fenthion, methidathion, parathion, parathion-methyl, and quinalphos) in orange fruit was studied in real operating conditions, to evaluate if residues after the pre-harvest interval (PHI) were within the limits established by Italian law. The residues of these active ingredients were only found in the fruit peel with the exception of dimethoate, which showed a very low initial residue in the fruit pulp that was no longer detectable after the PHI. The decay rates of chlorpyrifos-methyl, dimethoate, fenthion, parathion, and parathion-methyl were such as to ensure respect of the maximum residue limits, Quinalphos residues were not always below the legal limit, mostly because the limit is too low (0.1 ppm), Methidathion showed a remarkable persistence; after the PHI (69 d), its residues were still above the legal limit.