(1)  Location. A Prunus seed-block shall be located not less than 300 feet from any nonregistered flowering plant of the Prunus species. The ground in a seed-block and for a distance of 20 feet surrounding the seed-block shall be kept clean cultivated or in an approved, controlled ground cover. Care shall be taken in the use of pollinizing insects and pollen application to prevent the transmission and spread of virus diseases through the use of infected pollen and/or its application. Each tree shall bear a permanent registration number.

(2)  Acceptability. The rootstock and top-stock sources of the seed-tree shall have originated from foundation trees established under this program or from virus-tested trees originating through the Inter-regional Project No. 2 (IR-2)  . If the tree is scion-rooted, its source shall have met the above requirements. Only registered trees shall be permitted in the seed-block.