Check out this piece (and definately follow the link) by immigration expert Mark Krikorian over at NRO's The Corner:
RE: CHEAP FARM LABOR [Mark Krikorian]The prosecution rests, your honor...
A reader suffers from some common misconceptions about immigration and agriculture: "Do you want to depend on foreign food imports to feed the U.S.A.? Because that cheap foreign labor and state subsidized agriculture is already hurting the U.S. farmer. You better look at the big picture quick! You think our citizens are pissed about foreign oil dependence, think what they will do if they go to the grocery store and the shelves are empty?" In fact, no immigrant, or anyone else, ever touches the corn, wheat, soy beans, etc. that account for the bulk of farming -- foreign labor is concentrated in the harvest of fresh fruits and vegetables. And if you look at the actual numbers, you'd see that since labor accounts for such a small part of the retail price fruits and vegetables, giving farm workers a 40 percent raise would increase grocery costs for the typical American consumers by $8 a year. Eight dollars. A year.