Among the tree-lined bike paths, automated livestock pens and darkened lecture halls of the University of California at Davis, a tiny room holds a weapon of mass destruction. Here, behind locked doors, sits a chunk of Xanthomonas, a bacterial blight that has decimated rice harvests in China, India, Indonesia, Malaysia, the Philippines, Thailand, Vietnam and West Africa. Since the passage of the Bioterrorism Preparedness and Response Act of 2002, the U.S. Department of Agriculture has deemed Xanthomonas a "select agent," which meant that in order to enter I had to produce a photo I.D., sign a series of documents, and suit up in a disposable lab coat. Within the restricted area, a staff researcher snapped on a pair of rubber gloves, unlocked an incubator, and extracted a petri dish of yellowish goo, which he held a few inches from my outstretched hands. "I can't let you touch it," he said.