American farmers are beset by a "perfect storm" of difficulties to increasing production. Capital is restricted. Land is expensive. And labor is scarce. Some farmers have coped by setting up farming in Mexico, Brazil, and other nearby Latin American countries. But most farmers, especially small farmers, don't have the resources to expand abroad. Scarcity of harvest labor is one of the most difficult problems to solve. Across the US, illegal Mexican immigrant labor, supported by second and third generation Latin American labor, have provided most of the harvest labor. But crackdown on illegal immigration has made it difficult to obtain sufficient laborers. The argument is sometimes made that American citizens would do the labor if (a) they were paid enough and (2) if they didn't have to compete with illegals. But such temporary contract labor, aside from farm family members, has repeatedly failed to show up to do the job. Unemployment insurance and welfare support provide more income than farm labor and deprive American citizens of the incentive to do harvest labor. In the South, black labor has largely left the fields, with disinterest in doing harvest labor reinforced by memories of servitude.
During World War I and World War II, temporary worker programs brought Mexican laborers into California and Texas to do agricultural labor; but the national political consensus has resisted renewing such programs. In the 1960s and 1970s, the effort to unionize farm labor stigmatized the "bracero" programs as exploitative. Yet some form of temporary work visa program is inevitable, if American agriculture is not to stop growing crops that require hand labor at harvest.