Leak et Pink Rot
Pythium spp. et Phytophthora erythroseptica
Causative agent and transmission
Various oomycete fungi, belonging to the Leak and pink rot family, are liable to cause soft rot in tubers:
• the Pythium, particularly P. ultimum, wet rot agent.
• Phytophthora erythroseptica, pink rot agent.
These fungi can all remain alive in the oil for several years and require a high level of humidity to develop.
The Pythiums penetrate through wounds and develop more frequently in hot and damp conditions, particularly during stormy conditions during harvesting, while Pink Rot has a lower optimum temperature.
Description of symptoms on tubers
(clic on photos to enlarge)
• Pythium: initially a grey damp rot, then turning brown on contact with the air. The texture of the affected tissues is relatively fluid, even creamy and healthy, while the diseased tissues are clearly separated. The symptoms may develop if drying is insufficient
• P. erythroseptica: tuber rot often starting at the stem-base, with browning on the surface and inside; the pink-coloured affected areas are separated from the healthy areas by a blackish line. The tissues become elastic but retain their consistency, unlike bacterial rot. On the cut surface, the pink areas turn brown in one hour.
Control
- Use of healthy seed potatoes;
- Crop rotation;
- Rapid drying and good ventilation during storage;
- Plot drainage if necessary.
