Relative Toxicity of Selected Insecticides to Bacterial Populations in Waste Disposal Lagoons

Abstract

The toxicity of several insecticides to bacterial populations in waste-disposal lagoons was compared at five concenntrations. Dursban® ( O, O -diethyl O -(3, 5, 6-trichloro-2-pyridyl) phosphorothioate) and naled caused the highest levels of mortality to the bacterial population, having LD50’s of 0.028 and 0.02%, respectively. Abate® ( O, O -dimethyl phosphorothioate O, O -diester with 4, 4'-thiophenol) and fenthion with LD50’s of 0.9 and 0.66%, respectively, caused the lowest mortality. Bacterial mortality as low as that found in tests using 0.0001% (1 ppm) concentrations would probably not cause a functional disruption of the lagoon process. To control mosquito breeding the daily addition of fecal material along with bacterial development in a lagoon could offset the bacterial mortality caused by insecticide application at 1 ppm or less.