When you force-feed caterpillars high concentrations of Bt pollen, they die. In November 1999, a panel of researchers met in Chicago to present the results of actual field studies of Monarch Butterflies. Bt corn pollen concentrations fall off very rapidly a short distance from the cornfield. Pollen concentrations on milkweed leaves near cornfields generally aren't high enough to harm Monarch larva and other non-target moths and butterflies. Monarchs apparently do not like Bt corn pollen and avoid it when possible.
Cornfields contain very few milkweed plants.
The reliability of the Iowa State study was discussed by Anthony Shelton, associate director of research at Cornell University, where another flawed Monarch Butterfly study received widespread coverage about a year earlier. Shelton had been very critical of the Cornell study, even though it was conducted at his own university. More detailed and extensive field studies are being done by a group of independent scientists from the United States and Canada. Truth fares poorly in the press The Environmental Protection Agency has been monitoring Bt corn research since the corn was first approved for sale in the United States. The media's crusade against Bt corn was launched by a single study, poorly designed, poorly implemented, and reporting results that were not statistically significant.