Whenever 25 per centum of the producers in an area who seek an amendment of the order file a written petition duly signed by them, the same procedure adopted herein for the issuance of an original order shall be followed. If after hearing the commissioner shall find the existence of conditions referred to in section 292 of the Agriculture and Markets Law which will result in an unreasonable or unnecessary economic waste with respect to the agricultural commodity covered by the hearing notice, only the amendment or amendments shall be submitted to a referendum vote and the approval of 50 per centum of such producers participating in the referendum vote shall in such event be required to effectuate such amendment or amendments. As in the case of the promulgation of an original marketing order, an amendment thereof shall be accompanied by a written decision of the commissioner reciting the referendum vote and containing a certification of said 50 per centum approval. If after such hearing the commissioner shall not find the existence of said conditions he shall render a decision in accordance with his finding and shall not submit the proposed amendment or amendments to a referendum vote. If the commissioner, in the absence of a petition, shall move to amend an order pursuant to subdivision 2 of section 294 of the Agriculture and Markets Law, he shall hold a hearing on notice as set forth in section 200.4 of this Part and shall follow the procedure respecting decision as stated in this section.