(a) Prior to the beginning of each marketing season or as soon thereafter as possible, the commission shall establish an assessment rate for the marketing season.
(b) The assessment rate for producers shall not exceed 1 percent of the gross dollar value of winegrapes marketed by producers to vintners. If a producer sells winegrapes for a specified sum in a bona fide sale, the gross dollar amount of this sum is the gross dollar value of the winegrapes.