Increase of Persistence and Toxicity of Parathion and Diazinon in Soils with Detergents12

Abstract

Addition of the detergents ABS (alkyl benzene sulfonate) and LAS (linear alkyl benzene sulfonate) to insec-ticide-treated soils, increased the persistence of organo-phosphorous insecticidal residues. Parathion and diazinon were especially affected by these soil treatments. Two months after the insecticidal and detergent applications to a silt loam, 13 times more parathion and 5 times more diazinon residues were recovered from these soils as compared with those which had only been treated with the insecticides and were free of detergents. Treatment of soils with commercial formulations of parathion or diazinon, to which LAS had been added, also resulted in an increased persistence of these insecticides in a loam soil. Populations of microorganisms in soils increased due to the presence of ABS or LAS. Soils not treated with detergents showed an average count of 4.33 million bacteria per gram of dry soil, but in the presence of ABS or LAS the soils contained 56.7 million and 228 million, respectively. LAS applied topically to house flies, Musca domestica L., with parathion, diazinon, and dieldrin in a 1: 1 or 10:1 ratio did not affect the toxicity of these insecticides. How-ever, when LAS was mixed into soil treated with parathion or diazinon a synergistic effect on both insecticides was noticed. Increasing concentrations of LAS caused in creased toxicities to Drosophila melanogaster Meigen until an optimum was reached, when the insecticides and detergents were used in a 1:1 ratio. This was followed by a decrease in the toxicity of the insecticides as the LAS con-centration increased, resulting finally in a masking effect of the insecticidal activity through the presence of LAS at a concentration of 4600 ppm. With parathion and diazino, the optimum synergistic effects were achieved with LAS at 23 ppm. At this point the toxicities of parathion and diazinon were significantly increased by factors of 2.39 and 1.64, respectively.