If the Department finds that a nursery is infested or infected with insect pests or plant diseases, or if the Department shall have reason to believe that a nursery, by way of its proximity to an infested or infected premises, will become so infested or infected before the next annual inspection, the Department may prescribe in writing such conditions and precautions as to the use of the certificate of inspection, as may in its judgment be necessary. The Department may withhold or suspend a certificate until such conditions have been accepted in writing by the owner of said nursery. The unlawful use of a conditionally issued certificate of inspection shall be a violation of this Act.