Some Florida orange growers are getting smart and using machines rather than foreign serf labor. From the NYT:

IMMOKALEE, Fla. - Chugging down a row of trees, the pair of canopy shakers in Paul Meador's orange grove here seem like a cross between a bulldozer and a hairbrush, their hungry steel bristles working through the tree crowns as if untangling colossal heads of hair.

In under 15 minutes, the machines shake loose 36,000 pounds of oranges from 100 trees, catch the fruit and drop it into a large storage car. "This would have taken four pickers all day long," Mr. Meador said...

But as globalization creeps into the groves, it is threatening to displace the workers. Facing increased competition from Brazil and a glut of oranges on world markets, alarmed growers here have been turning to labor-saving technology as their best hope for survival...

"The rest of the world hand-picks everything, but their wage rates are a fraction of ours," said Galen Brown, who led the mechanical harvesting program at the Florida Department of Citrus until his retirement last year. Lee Simpson, a raisin grape grower in California's San Joaquin Valley, is more blunt. "The cheap labor," he said, "isn't cheap enough..."

Investment in technology generally happened when the immigrant spigot was shut. After the bracero program ended and some farm wages began to rise, scientists at the University of California at Davis began work on both a machine to harvest tomatoes mechanically and a tomato better suited to mechanical harvesting...

In line with the last paragraph, consider this quote from "The Mirage of Mexican Guest Workers":

...California Farmer reported in 1963 that if the flow of braceros stopped, tomato growers and canners "agree the State will never [again be able to plant] the 100,000 to 175,000 acres planted when there was a guaranteed supplemental labor force in the form of the braceros..."

Reality, however, never confirmed these dire predictions. In 1960 some 45,000 farm workers (mostly braceros) had harvested 2.2 million tons of processing tomatoes. By 1999, it took only 5,000 workers to operate machinery that harvested some 12 million tons. Thanks to these efficiency gains from mechanization, the real price of processing tomatoes declined 54 percent while per capita consumption rose 23 percent...

California Farmer was lying in 1963, and the same groups are lying today.