As weeds across large swaths of the Midwest have developed a resistance to Monsanto Co.'s "Roundup" herbicide, Dow AgroSciences LLC is asking the Department of Agriculture to sign off on a new genetically engineered corn seed that is resistant to not only Roundup, but also 2,4-D, a World War II-era chemical that has been associated with a host of serious health problems. But some farmers fear that if the corn is approved, the use of 2,4-D will also shoot up, eventually leading to weeds that develop their own resistance to the chemical. Go to story #1