Risk factors

Factors particularly favourable for potato late blight include temperatures in the range of 15-20°C, a high level of humidity and excessively dense foliage.

Depending on the temperature, sporangia germinate directly or release biflagellate zoospores. In optimum conditions, the length of the infective cycle is 3 to 5 days; this explains the explosive nature of the epidemics and the extremely rapid development of the disease.

The susceptibility of potato cultivars is a major factor in the epidemic development of potato late blight, although most cultivars are (moderately to very) susceptible to the disease.