Some migrant workers in the United States travel the same route from the south to the north each summer to work as laborers in Fields this is referred to as

Migrant farmworkers.

Explanation:

Migrant farmworkers are those migrant workers which goes from one place to another for work at agricultural farms at the harvesting month of crop or picking time of different fruits from trees. Migrant farmworkers are also known as migrant agricultural workers. These migrant workers work in a field as laborers and when the work is done, they go to their places from where they have come.