WASHINGTON, July 18 -- Sen. Susan M. Collins, R-Maine, issued the following news release: Senators Susan Collins and Angus King joined 16 of their Senate colleagues in sending a bipartisan letter to U.S. Department of Agriculture Secretary Thomas Vilsack expressing their serious concerns about the potential of potato wart spreading from potato imports originating from Canada's Prince Edward Island (PEI). In the letter, the Senators urged for the implementation of additional mitigation measures  more PR