A paper from Cornell University (Losey et al., 1999) was the first to report toxicity of Bt corn pollen to monarch butterflies. Although there was wide discussion in the scientific community that the study was preliminary and flawed in terms of how well it represented real-world issues (Berringer, 1999; Hodgson, 1999; Rice 1999; Shelton and Rousch, 1999), it received wide distribution in the popular press and used as an argument against further development and release of transgenic crops.

An Iowa State University study by Hansen and Obrycki (2000) was reported to corroborate Losey’s study, and under field conditions. Although a portion of the experiment was conducted in the field (unlike the laboratory study by Losey), critics contend that the study did not truly represent field conditions and didn’t accurately portray risks of Bt pollen in natural field settings. As was true for the Losey study, the results were widely circulated by the popular press, while criticisms of the experimental design and conclusions drawn by the authors were not mentioned by the media. Conversely, a study by Wraight et al. (2000) demonstrating an absence of toxicity of Bt pollen to black swallowtails under field conditions, received little or no circulation in the popular press. Additionally, numerous ongoing field studies showing minimal impact of Bt pollen on monarch butterflies have received no mention in the popular press.

This paper is not intended as further criticism of research conducted by Losey et al. (1999) and Hansen and Obrycki (2000). It is intended as a summary of those results, reasons why they may not be representative of field conditions and potential hazards of the pollen to monarch butterflies, and to point out the kinds of field research that are still needed.