Parathion persistence on South African citrus.

The fate of parathion applied to citrus was affected by rain, sun and wind, but not much by fruit variety, while the application method had an important effect. The formulation influenced the persistence of parathion on leaves and glass in the laboratory, but had no influence on the persistence on leaves or fruit in the field. The deposits of the emulsifiable concentrate and of the wettable powder and oil mixture were higher than that of the wettable powder alone, but since the rates of disappearance were the same, higher harvest-time parathion residues on and in the fruit resulted when the first two formulations were used. The time needed to reach a tolerance value increased for applications made later in the growing season.