LUBBOCK, Texas — The battle against red fire ants has plagued farmers, ranchers and regular folks for decades. Now it seems the reviled pests could be in for some sickness of their own. Researchers have pinpointed a naturally occurring virus that kills fire ants, which arrived in the U.S. in the 1930s and now cause $6 billion in damage annually nationwide, including about $1.2 billion in Texas. The virus caught the attention of U.S. Department of Agriculture researchers in Florida in 2002. The agency is now seeking commercial partners to develop the virus into a pesticide to control fire ants....