At Chandler Farms, just outside of Selma, Calif., in the San Joaquin Valley, about three dozen workers are needed each season to pick acres of delicate peaches, plums, nectarines and citrus.

In recent years, however, owners Carol and Bill Chandler have struggled to find laborers as immigration from Mexico has slowed to a near-standstill.

“When the crops are ripe, we need a reliable labor force,” she said. “That’s what we’re worried about going forward.”