Date of Award
Doctor of Philosophy
Jon J. Tollefson
Monsanto Co. (St. Louis, MO) has received approval for the commercial sale of transgenic corn (Zea mays L.) modified to produce insecticidal protein (Cry3Bb1) from the soil bacterium Bacillus thuringiensis Berliner (Bt) for control of the western corn rootworm larvae, Diabrotica virgifera virgifera LeConte and northern corn rootworm, D. barberi Smith and Lawrence; southern corn rootworm. This new technology could help reduce the amount of pesticides applied to corn fields for control of these pests and provides an alternative management strategy. The first objective was to determine if the fitness of beetles surviving from transgenic corn was affected. Female adults emerging from transgenic treatments were the same size as females from terbufos and isoline treatments but laid fewer eggs. Transgenic corn did not affect percent egg hatch. Females from YieldGard Rootworm and terbufos flew significantly shorter distances than females from isoline and YieldGard Plus treatments. Virgin females from did not fly sustained flights. Mated females from isoline and transgenic treatments flew farther than virgin females. The second objective was to examine similar questions but of adult beetles who had been exposed to the leaves and silks of transgenic plants. Beetles exposed to leaves or silks of transgenic plants did not fly significantly different than beetles exposed to nontransgenic plants. Beetles caged on leaves of transgenic plants for 5 days had higher mortality, consumed less leaf area, and laid fewer eggs than beetles caged on leaves of nontransgenic plants. Very little mortality occurred in beetles exposed to the silks of transgenic plants. Exposure to silks of transgenic plants did not affect egg laying or adult longevity. The third objective was to evaluate farmer perceptions and attitudes of transgenic corn using a survey. When asked if they would plant transgenic corn protected again the corn rootworm, 35.0% responded they would while 40.5% said they were unsure. The two biggest concerns farmers had of transgenic corn was the ability to sell harvested grain and additional technology fees. Farmers felt that less insecticide in the environment and less insecticide exposure to farmers were significant benefits of transgenic corn. The most common refuge-planting options farmers favored were adjacent fields and split fields.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu
Ted A. Wilson
Wilson, Ted A., "Fitness of the western corn rootworm, Diabrotica virgifera virgifera LeConte, exposed to transgenic plants and farmer perceptions of transgenic corn " (2003). Retrospective Theses and Dissertations. 1401.