Yet another report has raised the prospect that pollen from Bt corn is toxic to Monarch butterflies. However, as the results were based on the ingestion of pollen in the laboratory, rather than under field conditions, the new results are likely to do little to change opinions on either side of the debate.

Researchers from Iowa State University published, in Oecologia, that milkweed plants grown within 3 meters of fields planted with Bt corn - YieldGard or KnockOut varieties from Novartis Seeds Inc. (Golden Valley, Minn.) - carried an average of 135 pollen grains/cm2. In subsequent laboratory tests of leaf disks carrying that amount of pollen, 37-70 percent mortality of Monarch butterfly larvae was observed at 120 hours following a 48-hour exposure.