Influence of Soil Type on the Activity of Insecticides in Soil1

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Abstract
The bioactivity of 5 insecticides: heptachlor, DDT [dichlorodiphenyl trichloroethane], diazinon, parathion, and Nemacide [O-(2,4-dichloro-phenyl) O,O-diethyl phosphorothioate] was determined in 10 soil types. Both dry and moist soils were tested. First-instar nymphs of a common field cricket, Acheta (=Gryllus) pennsylvanlcus (Burmeister), were used as the test insects. In moist soils bioactivity was dependent on the organic content of the soil. The relationship was curvilinear with the degree of inactivation also being dependent on the specific insecticide used. Heptachlor was less active by a factor of 209, diazinon by 283, Nemacide by 546, DDT by 965, and parathion by 1132 in muck soil containing 64.6% organic matter than in Quartz sand. In dry soils there was no direct correlation between organic content and bioactivity. Heptachlor and DDT appeared to be inactivated by the clay fraction, diazinon and parathion by the sand or silt fraction, and Nemacide by both fractions. The presence of moisture resulted in activation of all insecticides in mineral soils, but not in muck soils. Based on the data obtained it is suggested that at least 3 separate bonding mechanisms may occur.