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Bob Hartzler / Iowa State University

New herbicide-resistant corn and soybeans are a step closer to reaching farm fields in the U.S. They would help farmers control weeds that are no longer killed by the popular herbicide, Roundup.

Roundup resistant crops dominate corn, soybean and cotton production in the U.S. But the list of weeds that have evolved to withstand Roundup is growing, and as a result, farmers are using more chemicals to keep up.