For enabling the director of the department of agriculture to investigate and certify to shippers and other interested parties the quality and condition of fruits, he shall, upon request of interested parties, inspect or cause to be inspected as to condition and grading by authorized inspectors, by him appointed, any or all fruits prepared or being prepared for shipment and is hereby authorized to issue certificates of inspection to said shippers or other interested parties, certifying as to the condition and grade of such fruits, under such rules and regulations as he may prescribe, including payment, by party requesting such inspection, of such fees as will be reasonable and as nearly as may be to cover the cost for services rendered. In carrying out the provisions of this chapter the director may cooperate with the United States department of agriculture or other inspection agencies.