Bioactivity and Persistence of Some Parathion Formulations in Soil2

Abstract

The persistence and biological activity of parathion in soil was studied under laboratory and field conditions. Microbial breakdown appeared to be the major contributor to the loss of parathion in soil. Although moisture and soil type influence parathion degradation, this influence is mediated primarily by the activity of microorganisms. Highest biological activity against larvae of the western corn root worm, Diabrotica virgifera LeConte, on soil was achieved with broad distribution and minimum binding of parathion (e.g., 1% kaolinite dust; LD50 = 0.05 ppm) whereas low activity was associated with tightly bound, thinly distributed formulations (e.g., 10% on charcoal; LD50 = 6.0 ppm). However, chemical assays of soil showed that the dust was the least persistent and the charcoal the most persistent formulation (50% breakdown in 6 days vs. 72 days, respectively).