Presentation on theme: "A monarchs risk to genetically engineered corn Meghann Grant Biology Department Eastern Connecticut State University."— Presentation transcript:
A monarchs risk to genetically engineered corn Meghann Grant Biology Department Eastern Connecticut State University
Impact of Bt corn pollen on monarch butterfly populations: A risk assessment Proc. Natl. Acad. Sci. Vol. 98:21, pp11937-11942 Mark K. Sears, Richard L. Hellmich, Diane E. Stanley-Horn, Karen S. Oberhauser, John M. Pleasants, Heather R. Mattila, Blair D. Siegfried, Galen P. Dively
Bacillus thuringiensis corn pollen Corn is the 2 nd most genetically engineered crop Engineered to control the pest, the European corn borer Wind pollination causes toxins to land on Asclepias syriaca 1999, EPA claims that monarch and larvae exposure to Bt is limited
Components of risk assessment Bt * production and distribution * Bt expression * pollen shed (timing, duration, intensity) Monarchs * occurrence and distribution (Corn Belt, landscape) * habitat * behavior
Milkweed * occurrence and distribution * landscape (ecosystem) * habitat (abundance in corn)
Materials and methods monarchs and larvae leaf discs pollen several toxins Iowa, Maryland, New York, Ontario pollen is shed over a 2 week period in late July
Questions that need answers Is there some density of Bt pollen on milkweed leaves that represents a lethal threat to monarch larvae or later stages of development? What proportion of Bt pollen deposited on milkweed leaves in and around corn fields exceeds the toxicity threshold for larvae and monarchs? What proportion of monarch populations use milkweed in and near corn fields? What is the degree of overlap between the phenological stages of monarch larvae and corn anthesis over the shared range of these species?
Conclusions Cry1Ab protein is toxic in event 176 hybrids only comprise less than 2% corn acres overall exposure to Bt pollen is low even at low pollen densities, growth inhibition and mortality is evident findings from multiple studies done in other locations were consistent
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