Risk factors

With both types of scab, infection is via the lenticels during tuber formation and the disease does not progress further during storage. Generally speaking, common and netted scabs are favoured by light, aerated soils.

• Common scab (raised or pitted scab)

The appearance of this disease depends on the cultivar (different levels of susceptibility), on the temperature (optimum temperature 19 to 24°C) and on soil moisture (the disease is favoured by dry, aerobic conditions).

• Netted scab

The appearance of this disease depends mainly on the cultivar used as only a few of them are susceptible and most potato cultivars are resistant to netted scab. The disease thrives in a cool temperature (13 to 17°C) and wet soil.