Destructive weed threatens U.S. corn fields

A U.S. government program designed to convert farmland to wildlife habitat has triggered the spread of a fast-growing weed that threatens to strangle crops in America's rural heartland.The weed is hard to kill and, if left unchecked, destroys as much as 91 percent of corn on infested land, according to the U.S. Department of Agriculture (USDA). It is spreading across Iowa, which accounts for nearly a fifth of U.S. corn production and in 2016 exported more than $1 billion of corn and soy.The federal Conservation Reserve Program pays farmers to remove land from production to improve water quality, prevent soil erosion and protect endangered species.The destructive weed - Palmer amaranth – has spread through seed sold to farmers in the conservation program, according to Iowa's top weeds scientist, Bob Hartzler, and the conservation group Pheasants Forever."We are very confident that some of these seed mixes were contaminated," Hartzler said.Hartzler, an Iowa State University agronomy professor, said one seller was Allendan Seed Company, the state's largest producer of local grass and wildflower seeds for conservation land. Palmer amaranth first arrived in Iowa in 2013 but exploded across the state last year, spreading from 5 to 48 of the state's 99 counties, according to Iowa State University. In at least 35 of those counties, the weed was found on land in the conservation program.