Genetically modified (GM) foods have been the source of heated debate, with GM corn often at the center of controversy. American corn farmers have faced a constant battle with the corn borer, a voracious insect that costs farmers nearly $1 billion a year in pesticides and other measures to prevent damage to corn crops. In 1995 scientists from Plant Genetics Systems developed corn seed it called StarLink, which contained a corn borer–killing gene that poisoned the borer, saving farmers time and money. Because StarLink contained a protein, Cry9C, that resembled a substance found to trigger violent allergies in some people, U.S. federal regulators threatened to ban it. Aventis, a European pharmaceutical company that had purchased Plant Genetic Systems, asked if it could instead sell the StarLink seed to farmers who would use it only for feed corn...