Pythium spp.

(Leak rot or Watery wound rot)

• Causal agent and transmission

Several types of wet rot can be found on potato tubers. They are caused by various Oomycetes, belonging to the family Pythiaceae, such as several species of the genus Pythium, namely P. ultimum, which cause watery rot (also called watery wound rot or leak rot).

This pathogen can survive in the soil for several years as thick-walled oospores and has a wide host range on which it is often the cause of the damping-off of seedlings.

• Significance

Watery wound rot can be very damaging to potato crops, his occurrence in continental Europe is fairly uncommon. Nevertheless, due to elevated optimal growth temperatures (above 20°C for both), there is a small risk of the disease occurring in southern European countries.