Common Scab is a very common disease of potatoes and is widespread throughout the country and is naturally present in most soils. It can also affect beetroot, radish, swedes and turnip. Severe attacks are most likely to occur on light, sandy, alkaline soils with a low organic matter content and in hot, dry summers. Freshly broken up grassland or ground soil rendered alkaline by the addition of lime contributes to the occurrence of this disease.

Variable forms of skin roughness occur, developing most commonly into angular rather corky scabs which may either be raised or depressed. The scabs may occur singly or in groups, sometimes in severe cases covering almost the entire surface.

Since this form of scab is usually no more than a skin deep, it should neither affect the keeping quality of the tubers, nor their culinary use, but slightly deeper peeling may be necessary. Storing the tubers does not spread common scab.

In the case of seed tubers severe scab may cause some blindness but there are usually enough eyes left to ensure a good crop. As the disease is so widespread and dependent on soil conditions the planting of affected seed potatoes does not usually result is transmitting additional infection to the resulting crop.

On light sandy soils dig in a Green Manure prior to planting, if grass cuttings are used the lawn must not have been treated with a weed killer within the last six to eight weeks. Lime should not be applied as this can encourage the disease. Keep the plants well watered in dry spells when the tubers are forming. Do not add infected tubers and peelings to the compost bin.

The following potato varieties show some resistance Aran Pilot, King Edward and Swift.