The following is meant to provide basic information on migrant agricultural workers in Canada.
Workers come from several countries to work in Canada on temporary and very precarious work visas allowing them to stay anywhere from 3 months to 2 years to work in areas that have been indentified by federal or provoncial governments as suffering from labour shortages. The underlying system that permits these workers to actually enter Canada on temporary work permits is part of a much more intricate and complex structure set up by the federal government in 1966.
While migrant workers started out working on farms, they have gradually been working in more and more areas and under conditions that most Canadians would not accept.
To learn more about the origins of the program read this from Migration News
The Migrant agricultural program was initiated by the Federal government. 20 000 workers and employers agree to the terms of a same contract 2008 version in pdf
other documents worthwhile reading
United Food and Commercial Workers annual report on the situation of migrant workers in Canada (UFCW funds Support Centers for migrant workers throughout Canada) 2007 report in pdf