There are 3 million immigrant and migrant farm workers in the United States. Collectively, they pick the majority of fruits and vegetables that are sent to grocery stores and farmer's markets across the United States. The 77 percent who are foreign born also send home millions of dollars to family in Mexico and other parts of Central America. But tough talk on immigration coming out of Washington, D.C., these days could make it harder for agriculture companies to hire seasonal farm workers, many of whom might be afraid to attempt to cross into the United States, even if they have seasonal papers to do so. But the biggest change coming to agriculture is not the debate over immigration, but the rise of the agribots that can pick fruit, shake pecans off trees, sort and stack plants and separate leafy vegetables from their roots.