Roundup's strangehold falters in face of new threats
                                
                                
                                    (Newser) -
                                    New breeds of “superweeds” are creeping across the Farm Belt, and shaking up the weedkiller and seed industries in the process. The long-dominant Roundup can't deal with immune invaders like pigweed, horseweed, and Johnsgrass, which has given rival chemical companies a chance to bring back old herbicides that Roundup...