[SJackson]

First, the farms are out in the country where there aren't many people, so they are mismatched to many of the sources of casual labor mentioned here. Unlike many businesses, one cannot move a farm to the inner city where jobless people are. Second, these are very seasonal, temporary jobs. The migrants would move from one area to the next to make a living.

If illegal migrant workers are available, legal migrant workers will be available. They'll just cost more.

[ClaireSolt]

Pretty simplistic. There are conditions where there is no supply. I had an experience in 91 of advertising for a secretary at $6.00/hr and getting 100 applicants. Four years later I needed a secretary and went without for months. Advertising and listing with agencies brought no applicants. Finally, I got one through a referral and paid a lot. That's how much conditions can change in a labor market.