Serious damage means any injury or defect which seriously injures the edible or shipping quality, or the appearance of the individual potato or the general appearance of the potatoes in the container, or which cannot be removed without a loss of more than 10 percent of the total weight of the potato including peel covering defective area. Any one of the following defects or any combination of defects the seriousness of which exceeds the maximum allowed for any one defect shall be considered as serious damage:
(a) Fairly smooth cuts such as are made by the digger, or by a knife to remove injury when both ends are clipped, or when more than an estimated one-fourth of the potato is cut away, or, in the case of long varieties, when the remaining portion of the clipped potato weighs less than 6 ounces; irregular types of cuts which seriously affect the appearance of the individual potato, or which cannot be removed without a loss of more than 10 percent of the total weight of the potato including peel covering defective area.
(b) Shriveling, when the potato is excessively shriveled, spongy, or flabby.
(c) Surface scab which covers an area of more than 50 percent of the surface of the potato in the aggregate.
(d) Pitted scab which affects the appearance of the potato to a greater extent than the amount of surface scab permitted or causes a loss of more than 10 percent of the total weight of the potato including peel covering defective area.
(e) Wireworm, grass root or similar injury, when any hole on potatoes ranging in size from 6 to 8 ounces is longer than one and one-fourth inches, or when the aggregate length of all holes is more than two inches; smaller potatoes shall have lesser amounts and larger potatoes may have greater amounts: Provided, That the removal of the injury by proper trimming, does not cause the appearance of such potatoes to be injured to a greater extent than that caused by the proper trimming of such injury permitted on a 6 to 8 ounce potato.