A seasonal comparison of parathion degradation on oranges in Arizona

A study comparing the leaf residue decay of parathion wettable powder (8 lbs per acre) on oranges was carried out on neighboring plots in Arizona beginning in October, 1975, and February, 1976. While identical amounts of parathion were present immediately after spraying and the half-life of parathion was the same in both months, there was, on the average, more parathion residue during February. Graphs of parathion and paraoxon levels over time differed between months (in excess of sampling variability). This most likely was due to the daily influences of climatological variables which were obviously different in October and February.