Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

William A. Weiler


The screening of pesticides to determine which were most inhibitory to bacteria was accomplished by testing the effects of 10 pesticides on 9 different organisms using the disk assay method. Results showed that Gram positive bacteria were more sensitive to all pesticides tested than were the Gram negative bacteria. In addition, the hormone herbicides were found to be the most inhibitory to these bacteria and 2,4-D (2,4-dichlorophenoxyacetic acid), a hormone herbicide, was chosen for subsequent in vivo studies.

A soil perfusion apparatus was used to determine the effects of 2,4-D in a typical soil ecosystem. Bacterial plate counts and nutrient analyses were used to determine the effects of the chemical on the soil bacteria and on their metabolic processes. Results shoved that 2,4-D significantly reduced bacterial populations and nitrate production within 2 weeks of application. Nitrate production was reduced to the point where none of the soil nitrogen found in the soil perfusate was present as nitrate.