When potatoes are marketed or offered for shipment, within the state of Idaho, for packing, repacking or processing purposes, or when potatoes are offered for sale by the grower direct to the consumer in lots of less than one (1) carload within the state or when "Idaho Certified" seed stock, as defined by the Idaho state seed certification officials are offered for sale, the provisions of this act prescribing grades and requiring grading shall not apply; but in all other cases when potatoes are packed for sale, offered for sale, sold, or offered for shipment within or outside the state of Idaho, such potatoes shall be graded either as "Idaho Deluxe," "Idaho Standard," or "Idaho Utility": provided, however, that all potatoes marketed within the state of Idaho or outside the state of Idaho may conform to grades promulgated by an act of congress or promulgated by authority of the secretary of agriculture of the United States, if the shipper or grower so desires. It is further provided that all potatoes not meeting the requirements of grade hereinabove provided for and hereinafter set out are hereby declared to be detrimental to the potato industry of the state of Idaho and shall not be marketed, except as provided in this section. All potatoes conforming to the grades hereinabove and hereinafter set out shall be packed in containers or bags in conformity with the following prescribed rules. When potatoes are to be shipped out of state in bulk, permission shall first be obtained from the Idaho department of agriculture. All permits issued hereunder shall be issued subject to the requirement that the potatoes to be shipped must be graded and must either meet the Idaho grades or the United States department of agriculture grades for potatoes; except that potatoes shipped outside the state for processing into some changed form or product do not need to be graded. The Idaho department of agriculture may promulgate the necessary rules and forms to carry out this paragraph.