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Impact of Bt corn pollen on monarch butterfly populations: A risk assessment
Proceedings of the National Academy of Sciences USA
  • Mark K. Sears, University of Guelph
  • Richard L. Hellmich, Iowa State University
  • Diane E. Stanley-Horn, University of Guelph
  • Karen S. Oberhauser, University of Minnesota - Twin Cities
  • John M. Pleasants, Iowa State University
  • Heather R. Mattila, University of Guelph
  • Blair D. Siegfried, University of Nebraska-Lincoln
  • Galen P. Dively, University of Maryland - College Park
Document Type
Article
Publication Date
10-1-2001
DOI
10.1073ypnas.211329998
Abstract

A collaborative research effort by scientists in several states and in Canada has produced information to develop a formal risk assessment of the impact of Bt corn on monarch butterfly (Danaus plexippus) populations. Information was sought on the acute toxic effects of Bt corn pollen and the degree to which monarch larvae would be exposed to toxic amounts of Bt pollen on its host plant, the common milkweed, Asclepias syriaca, found in and around cornfields. Expression of Cry proteins, the active toxicant found in Bt corn tissues, differed among hybrids, and especially so in the concentrations found in pollen of different events. In most commercial hybrids, Bt expression in pollen is low, and laboratory and field studies show no acute toxic effects at any pollen density that would be encountered in the field. Other factors mitigating exposure of larvae include the variable and limited overlap between pollen shed and larval activity periods, the fact that only a portion of the monarch population utilizes milkweed stands in and near cornfields, and the current adoption rate of Bt corn at 19% of North American corn-growing areas. This 2-year study suggests that the impact of Bt corn pollen from current commercial hybrids on monarch butterfly populations is negligible.

Comments

This article is from Proceedings of the National Academy of Sciences USA; 98 (2001); 11937-11942; doi: 10.1073ypnas.211329998

Rights
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.
Copyright Owner
National Academy of Sciences
Language
en
Date Available
2014-08-20
File Format
application/pdf
Citation Information
Mark K. Sears, Richard L. Hellmich, Diane E. Stanley-Horn, Karen S. Oberhauser, et al.. "Impact of Bt corn pollen on monarch butterfly populations: A risk assessment" Proceedings of the National Academy of Sciences USA Vol. 98 Iss. 21 (2001) p. 11937 - 11942
Available at: http://works.bepress.com/richard_hellmich/47/