SANGER, Calif. — Six months ago, workers at one of the largest fruit farms in the U.S. went to the ballot box to decide if they would continue to be represented by the United Farm Workers, which won that right two decades ago but never forged a labor contract.

The ballots, still uncounted by state officials and locked in a safe, sit at the center of a dispute between the union launched by iconic farm labor leader Cesar Chavez and Gerawan Farming, Inc., which hires more than 5,000 workers annually to tend and harvest nectarines, peaches and plums.