The US Environmental Protection Agency has delivered a major blow to the biotechnology industry by placing new restrictions on the cultivation of GM corn.
This is in response to concerns that gene-altered crops may be causing ecological disruption by promoting crops with resistance to pesticides.
The restrictions, which have immediate effect, make unprecedented demands on the producers of biotech seeds and on farmers who plant so-called Bt corn, which has been endowed with a gene that allows it to make its own insecticide.
Among new restrictions is a requirement that farmers plant conventional corn on 20 to 50 per cent of their acreage. Some experts predict this could lead to a decline in plantings of GM seeds.
Bt corn, which has an in-built ability to produce the natural toxin Bt, has enjoyed a meteoric rise in popularity among farmers since it was approved for sale in 1996, and was planted on more than a third of US corn acres last year.
Concern, nonetheless, has persisted, with fears that large-scale plantings of Bt corn may be accelerating the evolution of insects which are resistant to standard insecticides.
Research last year by Cornell University scientists presented preliminary evidence from laboratory studies that pollen from Bt corn could blow onto milkweed plants and kill monarch butterfly caterpillars prompted a rethink.
Much research is now concentrated on "gene-stacking" technology, which uses a variety of GM components in an effort to reduce the likelihood of resistance.
Although field studies aimed at measuring the ecological impact of Bt corn on monarchs are not yet complete, the EPA suggested farmers voluntarily plant conventional cornfields upwind of their GM fields so the Bt corn pollen would not blow onto these refuges. Milkweed, the only plant on which monarch butterflies lay their eggs, grows around cornfields.
Environmentalists welcomed the move, which the EPA negotiated with the biotechnology industry, as a step in the right direction. "What EPA has done is to confirm that there are some serious environmental problems concerning the widespread planting of Bt corn," Ms Rebecca Goldburg, a scientist with the Environmental Defence Fund, told the Washington Post.
Some GM corn varieties have been rejected by the EU and others because of environmental and health concerns. Rejections cost US farmers more than $200 million in exports last year. US trade experts are predicting sales of engineered corn may decline this spring for the first time.
The restrictions demand that farmers plant large "refuges" of conventional corn near their Bt corn to reduce Bt pressures on insects and delay evolution of resistance in pest populations.
Farmers will not be allowed to spray refuges with conventional insecticides unless they can prove that pests have exceeded certain levels.
