From the Report On Business Section Today June 2, 2007, of the Globe and Mail;

"Beginning yesterday, in a move it announced May 30, the U.S. government will start inspecting commercial trucks and loaded railway cars entering the United States from Canada for agricultural threats.

The U.S. Department of Agriculture says Canada is an increasing threat when it comes to unwanted plant pests entering the U.S., particularly from third-country products relabelled as Canadian and then exported in U.S-bound shipments."

The whole story here;

http://www.theglobeandmail.com/servlet/story/LAC.20070602.RTICKERMAIN02/TPStory/Business