United Farm Workers leader Dolores Huerta at the Delano grape workers strike in Delano, Calif., 1966. The strike set in motion the modern farmworkers movement. Jon Lewis/Courtesy of LeRoy Chatfield hide caption

The workers planting apple trees at this orchard in Wenatchee, Wash., came to the U.S. on temporary visas for farm workers. Dan Charles/NPR hide caption

Harvesting oranges near Arcadia, Fla. The sacks that workers carry weigh about 90 pounds when they are full of fruit. Dan Charles/NPR hide caption

Workers sort potatoes in the field, collecting small and large ones in different buckets. Each bucket weighs 30 pounds or so. A worker will shoulder that bucket and dump it into a flatbed truck 400 to 500 times a day. It's a daily load of 6 or 7 tons of sweet potatoes. Dan Charles/NPR hide caption

Jose Martinez in the Adams County, Pa., orchard where he's working this year. He's been coming to the county for the apple harvest for the past 13 years. Dan Charles/NPR hide caption

Filipino farmworkers, including Larry Itliong (left), were the first to walk out of vineyards, prompting the Delano Grape Strike. They would join forces with Mexican laborers led by Cesar Chavez to form the United Farm Workers. Farmworker Movement Documentation Project/University of California San Diego Library hide caption

The California Pepper Commission says mechanical harvesters to pick hot and bell peppers could help solve labor shortage problems. Bob Sacha/Corbis hide caption

Farmer Issiaka Ouedraogo walks past cocoa pods growing on a tree, on a cocoa farm outside the village of Fangolo, near Duekoue, Ivory Coast in May 2011. Rebecca Blackwell/AP hide caption

A Triqui Mexican picks strawberries at a farm in Washington state. Courtesy of Seth Holmes hide caption