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Tim T. Oien

Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Robert Todd


Every year approximately two billion kgs of synthetic pesticides are used in the world in an attempt to control harmful insects and invader plant pests. Many of these chemicals have proven to be adequate at control of various pest organisms, but recently they have failed to give control in many locations. Several theories have arisen to explain this phenomena, the main one being that a microbial population adapted to growth in the presence of these chemicals and was possibly stopping the act ion of the pesticides in some way. The basic purpose of this research was to: 1. Determine if there was an enhanced degradation in soil which had a previous history of pesticide usage, 2. Examine a crossover of degradation between two organophosphate pesticides, 3. Isolate the responsible organisms, 4. Test the individual organisms for degradative capabilities, and 5. To attempt identification of these organisms. My results demonstrated that there was enhanced degradation taking place when fonofos was applied repeatedly, but this effect was not observed with chlorpyrifos. There was also some crossover when chlorpyrifos history soils were treated with fonofos. The degradation observed could not be traced back to any one organism, leading the investigator to believe more than one organism was responsible. These observations could lead to a better pesticide development program and possible treatments for pesticide spills.

Library of Congress Subject Headings

Soils -- Pesticide content

Soil ecology

Soil microbiology



Number of Pages



South Dakota State University