7 C.F.R. § 51.3416 – Classification of defects.

External Defects
Defects	Maximum allowed for U.S. No. 1 processing	Maximum allowed for U.S. No. 2 processing
Air cracks	5% waste	10% waste.
Blackleg	5% waste	10% waste.
Bruises	5% waste	10% waste
Cuts	Smooth, not more than 10% of surface	Smooth, not more than 1⁄3 of surface.
Enlarged lenticels, discolored or sunken	5% waste	10% waste.
Flea Beetle	5% waste	10% waste
Folded end	5% waste	10% waste.
Fusarium tuber rot	5% waste	10% waste.
Grass, wireworm	5% waste	10% waste.
Greening, light	5% waste	10% waste.
Growth cracks	See Footnote No. 2	10% waste.
Grub	5% waste	10% waste.
Ingrown sprouts	5% waste	10% waste.
Nematodes	5% waste	10% waste.
Rhizoctonia, solid or thick mounded	Not more than 10% of surface	Not more than 25% of surface.
Rodent, bird damage	5% waste	10% waste.
Scab, pitted	5% waste	10% waste.
Scab, russet	25% of surface or 5% waste	50% of surface or 10% waste.
Scab, surface	25% of surface or 5% waste	50% of surface or 10% waste.
Scab, surface (elephant hide).	10% of surface or 5% waste	25% of surface or 10% waste.
Second growth	5% waste	10% waste.
Scaling, surface cracks—when cracked, thick and has depth	10% of surface or 5% waste	25% of surface or 10% waste.
Sunburn	5% waste	10% waste.
Sunken discolored areas	5% waste	10% waste.

Internal Defects
Defects	Maximum allowed for U.S. No. 1 processing	Maximum allowed for U.S. No. 2 processing
Occurring outside of or not entirely confined to the vascular ring
Internal Black Spot, Internal Discoloration, Vascular Browning, Fusarium Wilt, Net Necrosis, Other Necrosis, Stem End Browning	5% waste	10% waste.
Occurring entirely within the vascular ring
Hollow Heart or Hollow Heart with Discoloration	Area affected not to exceed that of a circle 7⁄8 inch in diameter in a 10 ounce potato. 1	Area affected not to exceed that of a circle 11⁄4 inches in diameter in a 10 ounce potato. 1
Light Brown Discoloration (Brown Center)	Area affected not to exceed that of a circle 7⁄8 inch in diameter in a 10 ounce potato. 1	Area affected not to exceed that of a circle 11⁄4 inches in diameter in a 10 ounce potato. 1
Internal Brown Spot and similar discoloration (Heat Necrosis)	Not more than the equivalent of 3 scattered spots 1⁄8 inch in diameter in a potato 6 ounces in weight or 21⁄2 inches in diameter, or correspondingly lesser or greater number of spots in smaller or larger potatoes	Not more than the equivalent of 6 scattered spots 1⁄8 inch in diameter in a potato 6 ounces in weight or 21⁄2 inches in diameter or correspondingly lesser or greater number of spots in smaller or larger potatoes.
1 Note: Or correspondingly lesser or greater areas in smaller or larger potatoes.