Any person, partnership, association or corporation, and any officer, agency, servant or employee thereof, violating any of the provisions of this subdivision shall be guilty of a misdemeanor for each offense. If any such person, partnership, association, or corporation shall be twice convicted of a violation of this subdivision, the commissioner of agriculture, markets, and food may prohibit him from marketing certified seed potatoes for a period of not less than 2 nor more than 4 years after such prohibition.