"In large sections of America's farmland, new strains of weeds are making life miserable for farmers. They've developed resistance to the country's No. 1 weedkiller, Roundup. Now farmers face a choice: Do they go for yet another kill-all-the-weeds chemical, or go back to more complicated, labor-intensive ways of fighting weeds?"

"Unless you grow cotton, corn or soybeans for a living, it's hard to appreciate just how amazing and wonderful it seemed, 15 years ago, when Roundup-tolerant crops hit the market. I've seen crusty farmers turn giddy just talking about it.

All they had to do was spray the herbicide Roundup over their fields and everything died — except their remarkable new crops, with their laboratory-inserted genes that made them resistant to that weedkiller.

Alas, the giddiness faded. In more and more places across the country, farmers now are struggling to deal with weeds that their favorite weedkiller won't kill anymore. The weeds, too, have evolved Roundup-resistance superpowers."

Dan Charles reports for NPR's The Salt blog March 7, 2012. [2]