The potential threat posed to the monarch butterfly by pollen from genetically modified corn has become something of a green cause celebre in the United States. However, preliminary results of studies announced last week in Chicago suggest the problem may not be as bad as had been thought.
Ongoing research suggests the pollen does not travel very far from the fields of corn that have been genetically modified to carry genes from the bacterium Bacillus thuringiensis (Bt), which makes the crop resistant to the European corn borer.
In the original study published in Nature, John Losey and a team from Cornell University had fed monarchs milkweed dusted with pollen from the Bt corn. This resulted in the butterflies eating less than usual and nearly half of the larvae dying.
The research provoked a storm as it was suggested that the Bt corn pollen could be dispersed by the wind to affect a large portion of the monarch population.
However, Stuart Weiss, a researcher at Stanford University who has been studying milkweed, the monarch's favoured food, said: "The worst-case scenario of this toxic cloud of pollen saturating the corn belt is clearly not the case."
Galen Dively, a University of Maryland scientist, said only trace amounts of pollen could be found on milkweed growing on land more than 3m from the corn fields. "The pollen drops off very rapidly beyond the edge of the corn field," he said.
The symposium was sponsored by the US Agriculture Department and the Agricultural Biotechnology Stewardship Working Group, which represents many biotech companies including Monsanto, Novartis, DuPont and AgrEvo.
Dr Losey, who attended the meeting, was unconvinced by the results and said more data would be needed to reassure him.