Bt Corn: Built-In Pesticide
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| Corn |
What is it?
Throughout the world, one out of every 25 cornstalks—totaling more than 20 million tons of corn—is destroyed each year by a caterpillar called the European corn borer. Once these pests burrow into corn stalks, they are out of reach of pesticide. So genetic engineers transplanted a gene from a species of bacteria, Bacillus thuringiensis, into corn, so that it produces a toxin that kills corn borers. One quarter of all corn now planted in the U.S. is genetically modified to produce this Bt toxin, as are millions of acres of cotton, potatoes, broccoli and other crops.
Pros and Cons
Advocates observe that Bt corn is more effective against the corn borer than conventional pesticides. By specifically targeting pests that eat corn, it reduces the need for pesticide sprays that can sicken farmers and wash into water supplies. But Bt corn may kill harmless insects, including monarch butterfly caterpillars, when corn pollen falls on the leaves they eat. Monarch and other butterfly populations do not yet appear to have declined in the field. But critics wonder why the threat to monarchs was not studied until after millions of acres of Bt corn had already been planted?
Bt Arms Race?
Continual exposure could make pests resistant to Bt—even in the natural form used by organic farmers. Instead of entering a high-tech arms race with pests, some argue, we should control pests with organic farming methods like intermingling and rotating crops.
Modified for Resistance/Tolerance
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| Soybeans |
Soybeans
Half the soybeans grown in the United States—about 75 million acres per year—are genetically modified to withstand herbicides. This built-in tolerance lets farmers spray fields with chemicals that kill weeds but leave crops unscathed. Supporters say these modified crops, including corn and canola, cut costs and improve yields, without affecting nutrition or safety. Critics say they offer no benefit to the consumer.
Yellow Squash
Plants get diseases, just like people. Viruses, bacteria and fungi all attack crops and ruin harvests—but genetic engineering can make plants impervious to certain diseases. A virus-resistant yellow squash has been grown in the U.S. since 1994—over the objections of critics who worry that the squash could pass its virus-resistance genes to wild gourds, perhaps creating a "superweed." Supporters say disease-resistant crops could help feed subsistence farmers in many parts of the world.
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| Grapes |
Chardonnay Grapes
The world's favorite variety of white wine is Chardonnay. If you try to grow Chardonnay grapes in Canada, however, the vines might die during Canada's harsh winters. Some native North American grapes, such as Vitis riparia, can handle the cold weather. So Canadian researchers isolated genes associated with cold-tolerance in Vitis riparia and are introducing these genes into Chardonnay plants. Other plants may be made cold tolerant by adding genes from organisms such as insects.
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| Barley |
Barley
Twelve percent of the world's farmland contains enough naturally occurring aluminum to stunt plant growth. Now scientists have identified a gene that enables barley and wheat to withstand high levels of aluminum. Transferring this gene to less hardy species makes them aluminum-tolerant, too. Modifying crops to tolerate salt, drought, extreme heat and toxic metals like cadmium and copper could double the word's usable farmland. These "supercrops" might also, however, take over wild areas.
Should These Foods be Labeled?
Who Decides?
Europe, Japan and Australia require labeling of genetically modified foods, but the U.S. requires labeling only if a genetically modified food product is "significantly" different from an unmodified one. Supporters say labels would simply scare people away from new products that could benefit farmers, consumers and the environment. Opponents argue that labels are needed because genetically modified products might not be completely safe, so consumers should have the right to choose.
No Easy Answers
Labeling GMO foods would require keeping them separate from unmodified foods at every stage of growth and preparation: separate fields, separate trucks, separate grain silos. Tracking GMO products from seed to supermarket would require costly, time consuming paperwork. But current segregation methods have failed on numerous occasions to keep GMO ingredients out of non-GMO foods.
Deciding which foods to label would be no simple matter. Highly processed ingredients like sugar, corn syrup and vegetable oil apparently contain almost no genetic material or proteins from the plants they came from. In Europe, refined oils are not labeled because they are considered chemically indistinguishable from non-GMO oils. We would have to decide where to draw the line regarding labeling soft drinks that contain GMO corn syrup; pork from pigs that eat modified soybeans; and cheese, bread, beer and yogurt made with enzymes from modified bacteria.
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