Since November 2009, when traces of the fish were found near Chicago, federal and state officials have used nets, electric shocks and poison to keep them out of the GreatLakes.
In the 1990s federal and state regulators agreed to make state limits more uniform for the GreatLakes' most toxic pollutants; Congress is now considering a bill to promote further collaboration.
The awful truth dawned only after a second opinion, by Zak Pretorius of the University of the Free State in South Africa: stem rust had not only lived on in a remote corner of Africa's GreatLakes.