The Commissioner may forgive ground rent for oyster leases in any area declared a disaster area for oyster culture. A disaster area may be declared when any natural or man-made condition arises which precludes satisfactory culture of oysters in that area. Such declaration for an area shall be made by the Commissioner upon the advice of the Director of the Virginia Institute of Marine Science on or before July 1 of each year, and ground rent due and payable in September following such declaration may be forgiven for the ensuing tax year. Such relief may continue until the Commissioner with the approval of the Virginia Institute of Marine Science declares the area again productive.