By splicing in a gene that allows crops to resist this plant-killer, farmers can apply it with abandon, cutting costs and reducing the need for tilling. But this success has sown the seeds of its own destruction by speeding the evolution of weeds—such as giant ragweed (Ambrosia trifida)—into varieties that also have inborn resistance to the herbicide. Now researchers at the University of Nebraska have successfully modified crops to resist yet another herbicide—dicamba—that would eradicate the ”pernicious weeds,” researchers report in Science.