Residues of fenthion and trichloron in olives and olive oil after olive tree treatments.

The residue levels of trichlorfon, fenthion and its metabolites were determined in olives, olive oil and vegetation water after treatment of olive trees at different times before harvest. The highest residues of fenthion were detected in oil, while the highest level of trichlorfon was found in vegetation water. The time gap between treatment and harvest strongly influences the residue levels of fenthion in olives and olive products. The levels of fenthion, which were lower than the maximum residue level (MRL) established by the Italian regulations, were obtained only when the treatment was carried out 60 days before harvest, so it may be necessary to use the insecticide trichlorfon 30 or 10 days before harvest since it leaves low residue levels in oils.