Upon receipt of a petition signed by at least ten percent (10%) of the pork producers in Idaho known to the association, the department shall notify the association and the association shall, within six (6) months, conduct a referendum upon the question of continuing the assessment. If a majority of the votes cast in the referendum are against continuing the assessment or if the association fails to conduct a referendum within the six (6) month period, the assessment expires at the end of the six (6) month period. If a majority of the votes cast in the referendum are in favor of continuing the assessment, then no subsequent referendum shall be held for at least three (3) years.