Onion bacterial soft rot (Pectobacterium carotovorum) – identify and control
Onion bacterial soft rot, Pectobacterium carotovorum was first reported in 1906 in France. This bacteria causes significant damage to seed crops, but it also severely damages consumer crops, both in the field and inside warehouses.
Symptoms. In bulb crops intended for storage, the attack of the bacterium occurs towards the end of the vegetation when, if the bulb is sectioned, it is observed that some fleshy leaves change their color, seem moist and sunken. In strongly attacked bulbs, the base disc will sink when pressing.
The bulbs that have been partially affected can completely rot if stored in humid warehouses or can become dried if stored inside dry atmosphere warehouses (in this case, only the exterior peels will be left from the bulb). The affected bulbs will release a strong, unpleasant smell.
For the onion and leek seed crops, the symptoms are also visible during the vegetation phase. The stems are poorly developed and during humid weather, wet mold will appear. The affected stems don’t reach the regular height, are stiff, the blossoming and fruition are reduced.
Onion bacterial soft rot is transmitted to leeks through infected seeds moving from one crop to another, and to onions through the vegetal debris.
Prevention and control. Phosphorus-based fertilizers, avoiding planting on moist and cold soils, but also a 3-year (minimum) crop rotation will limit the damage caused by this bacteria. During the vegetation period, specific fungicides can be administered.