Food and Farm Superweeds

**HOLD FOR STORY BY DAVID MERCER** In this photo taken June 1, 2010, central Illinois corn farmer Jerry McCulley sprays weed killer across his cornfield in Auburn, Ill. A handful of hardy weeds have adapted to survive Roundup, which many scientists say threatens to make the ubiquitous herbicide far less useful to farmers. (AP Photo/Seth Perlman)