Whenever any standard for the grade or other classification of any farm product becomes effective under this chapter, no person thereafter shall pack for sale, offer to sell or sell within this state any such farm product to which such standard is applicable unless it conforms to the standard, subject to such reasonable variations therefrom as may be allowed in the rules and regulations made under this chapter: provided, that any farm product may be packed for sale, offered for sale or sold without conformity to the standard or grade or other classification applicable thereto when such product will be consumed or used for manufacturing purposes wholly within this state, if it is not specifically described as state graded or packed under state standard, in accordance with such regulations as the department of agriculture may prescribe.