PERSISTENCE OF SOME ORGANOPHOSPHOROUS INSECTICIDES IN ORANGE FRUIT

The persistence of seven organophosphorous insecticides (chlorpyrifos- methyl, dimethoate, fenthion, methidathion, parathion, parathion-methy l, and quinalphos) in orange fruit was studied in real operating condi tions, to evaluate if residues after the pre-harvest interval (PHI) we re within the limits established by Italian law. The residues of these active ingredients were only found in the fruit peel with the excepti on 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-me thyl were such as to ensure respect of the maximum residue limits, Qui nalphos residues were not always below the legal limit, mostly because the limit is too low (0.1 ppm), Methidathion showed a remarkable pers istence; after the PHI (69 d), its residues were still above the legal limit.