Farmers used to worry about weeds. Then, herbicides solved that problem. At least for a while. In 1997, there were 432 new patents for herbicides; by 2009, there were only 65. Developing broad-spectrum glyphosate and 鈥淩oundup Ready鈥� crops worked so well that people basically stopped looking for new herbicides. But then the weeds started fighting back.
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