(Reuters) - German agrochemicals group Bayer AG has been blocked from selling its dicamba-based weed killer in the United States after an appeals court rejected a federal regulator's permit for the product.A three-judge panel ruled that the U.S. Environmental Protection Agency (EPA) substantially understated the risks related to the use of dicamba which is found in herbicides made by Bayer and its rivals.Environmental groups, which filed a lawsuit in 2018, wanted the court to force the EPA to..