Bt corn pollen impacts on nontarget lepidoptera: assessment of effects in nature.

Abstract

The demonstrations by Losey et al. (1) and Hansen and Obrycki (www.ent.iastate.edu/entsoc/nch 99/prog/abs/D81.html) that milkweed leaves dusted with heavy concentrations of Bt corn pollen are toxic to Monarch butterfly larvae (Danaus plexippus) feeding on them were consistent with the known toxicity of Bt endotoxin to Lepidoptera in general and the expression of Bt endotoxins in the pollen of the strains of corn they studied. Much speculation and some investigations followed, concerning the extent to which the poisoning of Monarch butterflies and other nontarget Lepidoptera might be significant contributors to the mortality of these insects in nature. For example, Shelton and Roush (2) were critical of the two earlier findings, but did not provide any data from nature, despite the fact that Losey et al. (1), in the original report, stated “it would be inappropriate to draw any conclusions about the risk to Monarch populations in the field based solely on these initial results.”