Biotechnology's promise to feed the world did not anticipate Trojan corn," "super weeds" and the disappearance of monarch butterflies. In the Midwest and South - blanketed by more than 170 million acres of genetically engineered corn, soybeans and cotton - an experiment begun in 1996 with approval of the first commercial genetically modified organisms is producing questionable results. Those results include vast increases in herbicide use that have created impervious weeds now infesting millions of acres of cropland, while decimating other plants, such as milkweeds that sustain the monarch butterflies. More than a million people have signed a petition to the Food and Drug Administration to require labeling of genetically engineered food. The stakes on labeling such foods are huge. The crops are so widespread that an estimated 70 percent of U.S. processed foods contain engineered genes. The U.S. Department of Agriculture has approved more than 80 genetically engineered crops while denying none. Genetically engineered crops ... have spawned an infestation of "super weeds" now covering at least 13 million acres in 26 states. The crops led to a 400-million-pound net increase in herbicide applications. Dave Mortensen, a weed ecologist at Pennsylvania State University, said the number of "super weed" species grew from one in 1996 ... to 22 today. Last month, scientists definitively tied heavy use of glyphosate to an 81 percent decline in the monarch butterfly population. It turns out that the herbicide has obliterated the milkweeds on Midwest corn farms where the monarchs lay their eggs after migrating from Mexico. Iowa State University ecologist John Pleasants, one of the study's authors, said the catastrophic decline in monarchs is a consequence of the genetically engineered crops that no one foresaw.