All assessments levied and imposed by this chapter shall be due prior to shipment and shall become delinquent if not paid within thirty days after the time established for such payment according to regulations of the commission. A delinquent penalty shall be payable on any such delinquent assessment, calculated as interest on the principal amount due at the rate of ten percent per annum. Any delinquent penalty shall not be charged back against the grower unless he or she caused such delay in payment of the assessment due.