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ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #124403
Title: TEMPORAL AND SPATIAL OVERLAP BETWEEN MONARCH LARVAE AND CORN POLLEN

Author
item OBERHAUSER, KAREN - UNIV OF MINNESOTA
item PRYSBY, MICHELLE - UNIV OF MINNESOTA
item MATTILA, HEATHER - UNIV OF GUELPH
item STANLEY-HORN, DIANE - UNIV OF GUELPH
item SEARS, MARK - UNIV OF GUELPH
item DIVELY, GALEN - UNIV OF MARYLAND
item OLSON, ERIC - UNIV OF MARYLAND
item PLEASANTS, JOHN - ISU
item LAM, WAI-KI - SOUTHWEST PURDUE AGRIC
item Hellmich Ii, Richard

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: A consortium of scientists has studied whether pollen from transgenic Bacillus thuringiensis (Bt) corn could be hazardous to the caterpillars of the monarch butterfly. These studies assess ecological risk by considering toxicological effect and environmental exposure. In this paper the likelihood that susceptible monarch stages will be exposed to Bt pollen is assessed. We studied milkweed and monarch densities in habitat types that comprise much of the land available to breeding monarchs: cornfields, cornfield edges, other agricultural fields, and nonagricultural areas. The study was conducted in four regions of the monarch breeding range. We found that monarchs use milkweed in cornfields throughout their breeding season, and that per plant densities are as high or higher in agricultural habitats as in non-agricultural habitats. Due to the prevalence of agricultural land, most of the monarchs produced in the upper Midwest are likely to originate in cornfields or other agricultural habitat. There was a greater temporal overlap between susceptible monarchs and corn anthesis in the northern part of the summer breeding (40-62%) than the southern part (15-20%), due to earlier pollen shed in the south. The importance of agricultural habitats to monarch production suggests that, regardless of the impact of genetically-modified crops, agricultural practices such as weed control and foliar insecticide use could have large impacts on monarch populations. This information will be useful for all stakeholders interested in the potential nontarget effects of transgenic plants.

Technical Abstract: To assess the likelihood that susceptible monarch stages will be exposed to Bt pollen, we studied milkweed and monarch densities in habitat types that comprise much of the land available to breeding monarchs: cornfields, cornfield edges, other agricultural fields, and nonagricultural areas. The study was conducted in four regions of the monarch breeding range. We found dthat monarchs use milkweed in cornfields throughout their breeding season, and that per plant densities are as high or higher in agricultural habitats as in non-agricultural habitats. Due to the prevalence of agricultural land, most of the monarchs produced in the upper Midwest are likely to originate in cornfields or other agricultural habitat. There was a greater temporal overlap between susceptible monarchs and corn anthesis in the northern part of the summer breeding (40-62%) than the southern part (15-20%), due to earlier pollen shed in the south. The importance of agricultural habitats to monarch production suggests that, regardless of the impact of genetically-modified crops, agricultural practices such as weed control and foliar insecticide use could have large impacts on monarch populations.