The secretary shall suspend or terminate any marketing program effective at the end of the then current marketing season whenever he finds, after a public hearing:
(a) The program is contrary to or does not tend to effectuate the purposes of this act.
(b) The termination or suspension is requested in writing by at least 51% of the affected producers, who produce at least 51% of the volume of the agricultural commodity, or by an association representing such numbers and volume.