If it is found that any certificate issued or approved by the Department is being used in connection with nursery stock or other plants which have not been inspected, or which are infested with insect pests or infected with plant diseases, or which are being sold, delivered or distributed without treatment being given or other precautionary measures prescribed by the Department being observed by the owner, or with the knowledge of the owner, is being used by persons other than the one to whom it was issued, without permission of the Department, the Director may require the owner of such certificate to appear before him, on a date specified, for a hearing to show cause why his certificate should not be suspended or revoked. If, after such hearing, the Director finds that such certificate has been wrongfully used in one or more of the ways specified in this Act, or if the owner of such certificate fails to appear at such hearing, he may issue an order suspending or revoking such certificate, and the use of such certificate, after it has been suspended or revoked shall be unlawful, and shall subject the owner thereof to the penalty prescribed in this Act. The Department may withhold a certificate of inspection from any person applying for the same if such person fails to comply with the requirements of the Department with reference to freeing his nursery and premises of insect pests and plant diseases and may refuse to certify a nursery if the same, for lack of care or from neglect, is in such condition that it cannot be adequately inspected.
     The Department may refuse to issue or may suspend the certificate of any person who fails to file a return, or to pay the tax, penalty or interest shown in a filed return, or to pay any final assessment of tax, penalty or interest, as required by any tax Act administered by the Illinois Department of Revenue, until such time as the requirements of any such tax Act are satisfied.