No claim or credit in any payment, accounting, or settlement shall be made or taken against a producer by any commission merchant, dealer, processor, or retail merchant for any damage to, or loss, dumping, or disposal, of any farm produce unless such claim or credit has been agreed to in writing by the producer and the licensee has secured and is in possession of a certificate issued by an agent of the department of agriculture showing that the produce has no commercial value, or a certificate issued by a county or state health officer, or other duly authorized officer, stating that the produce has been destroyed or otherwise disposed of as unfit for human consumption.