Improving Potato Skin Finish

Skin finish is becoming more important as consumers increasingly demand potatoes with clean, attractive skins, particularly when buying fresh or table stock potatoes. Tubers with surface infections such as black scurf, silver scurf, powdery scab or common scab are less attractive and also likely to have a reduced storage life.

Correct balanced nutrition of the will reduce the incidence of skin disorders and improve the skin finish. Calcium strengthens tuber skins providing better resistance to many diseases. Boron, magnesium and manganese can reduce levels of common scab. Zinc can minimise powdery scab. Sulphur may reduce both powdery and common scab infection.

Silver scurf and Common scab     Black scurf and Powdery scab


Calcium strengthens tuber skins providing better resistance to many diseases including black scurf silver scurf, powdery scab or common scab. These independent trials from the UK show the reduction in skin blemishes caused by a number of conditions following treatment with calcium nitrate.

Calcium and potato tuber skin blemishes


Sulphur helps to reduce the level of common and powdery scab. This effect may be due to a reduction in the soil pH where elemental sulphur is used. Best effects come from applying sulphur to the soil in a readily available form at planting, however a program of foliar sulphur, can also reduce infection.

Sulphur effect on common scab of potatoes


Boron helps stabilise calcium in the cell walls and also affects calcium absorption, so supplies are important to ensure a balanced nutrition and to maximizes the benefits of applied calcium. This trial shows how boron influences the calcium content of tubers and so also the incidence a range of skin disorders.


Zinc is commonly used to suppress powdery scab where the innoculum is at low levels. However, only soil applications are likely to provide sufficient zinc to have an effect on powdery scab and zinc should only be used as part of an integrated control strategy supported by other agronomic measures to limit soil infection alongside a choice of more resistant varieties.

Zinc effect on powdery scab of potatoes

Other crop management practices that improve potato skin finish

  • Avoid selecting fields where adverse factors such as disease, poor drainage or low water holding capabilities are present 
  • Selecting quality seed with less risk of disease
  • Disinfecting seed storage areas to reduce disease carry over
  • Irrigating to prevent, or minimise diseases such as common scab
  • Harvesting in good conditions to avoid physical damage and disease infestation.
  • Avoid liming immediately prior to planting potatoes as this will favour common scab
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