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United States Department of Agriculture

Agricultural Research Service

Title: Monarch Caterpillar Sensitivity to Bacillus Thuringiensis Purified Proteinsand Pollen

Authors
item Hellmich, Richard
item Siegfried, Blair - UNIV OF NEBRASKA
item Sears, Mark - UNIVERSITY OF GUELPH
item Stanley-Horn, Diane - UNIVERSITY OF GUELPH
item Daniels, Michael - ISU
item Mattila, Heather - UNIVERSITY OF GUELPH
item Spencer, Terrence - UNIV OF NEBRASKA
item Bidne, Keith
item Lewis, Leslie

Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 17, 2001
Publication Date: 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 laboratory tests were conducted to establish the relative toxicity of Bt toxins and pollen from Bt corn to monarch caterpillars. Toxins tested included Cry1Ab Cry1Ac, Cry9C, and Cry1F. Laboratory tests with purified Bt toxins indicate that Cry9C and Cry1F proteins are relatively nontoxic to monarch neonates, while neonates are sensitive to Cry1Ab and Cry1Ac proteins. Older caterpillars were 13 to 24 times less susceptible to Cry1Ab toxin compared with neonates. Laboratory tests with pollen suggest that pollen contaminants, an artifact of pollen processing, can dramatically influence caterpillar survival and weight gains and produce spurious results. The only transgenic corn pollen that consistently affected monarch caterpillar was from Cry1Ab event 176 hybrids, currently < 2% corn planted and for which re-registration has not been applied. Results from the other types of Bt corn suggest that pollen from the Cry1Ab (events Bt11, Mon810) and Cry1F, and experimental Cry9C hybrids, will have no significant adverse effect on monarch butterfly caterpillars in field settings. This information will be useful for all stakeholders interested in the potential nontarget effects of transgenic plants.

Technical Abstract: Laboratory tests were conducted to establish the relative toxicity of Bacillus thuringiensis (Bt) toxins and pollen from Bt corn to monarch larvae. Toxins tested included Cry1Ab, Cry1Ac, Cry9C, and Cry1F. Three methods were used: 1) purified toxins incorporated into artificial diet, 2) pollen collected from Bt corn hybrids applied directly to milkweed tissue, and 3) Bt pollen contaminated with corn tassel material applied directly t milkweed tissue. Bioassays of purified Bt toxins indicate that Cry9C and Cry1F proteins are relatively nontoxic to monarch neonates, while neonates are sensitive to Cry1Ab and Cry1Ac proteins. Older instars were 13 to 24 times less susceptible to Cry1Ab toxin compared with neonates. Pollen bioassays suggest that pollen contaminants, an artifact of pollen processing, can dramatically influence larval survival and weight gains and produce spurious results. The only transgenic corn pollen that consistently yaffected monarch larvae was from Cry1Ab event 176 hybrids, currently < 2% corn planted and for which re-registration has not been applied. Results from the other types of Bt corn suggest that pollen from the Cry1Ab (events Bt11, Mon810) and Cry1F, and experimental Cry9C hybrids, will have no significant adverse effect on monarch butterfly larvae in field settings.

Last Modified: 10/26/2014
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