A tractor growls, the packing trailer jerks into motion and Betancourt and his co-workers begin their routine: walk, stoop, cut, toss. Walk, stoop, cut, toss.

By the time the dense fog lifts from California's Salinas Valley, the crew has cut enough cauliflower to fill a dozen produce aisle bins at a local grocery store.

They will crisscross this and dozens of other fields eight hours a day, six days a week, for nine months, sleeping three to a room in hotels long since shunned by tourists. Come December, they'll board a bus and return to Mexico. Richer, they hope.

More than 11,000 foreign guest workers like Betancourt were approved last year to harvest the lettuce, fruit and vegetables for California's $47bn agricultural industry — a fivefold increase from 2011, according to Los Angeles Times analysis of U.S. Labor Department data.

If this year's hiring pace holds, that number will soar even higher.

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