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Soft Rot


Soft Rot

Usually appear in

All Year

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Caused By:-     Various Bacteria


Soft Rot is also called Bacterial Soft Rot as it is usually caused by various bacteria. Tubers, root and fruit are usually affected, but there is a wide range of host like potato, sweet potato, cassava, onion, cabbage and other crucifers, carrot, tomato, beans, corn, cotton, coffee, banana, and many other succulent plants.
Infected plant tissues first develop a water-soaked lesion That show signs of sinking inwards then enlarges rapidly in diameter and depth. The affected area becomes soft and mushy and generally turns a dark colour later in the disease development. Infected tissue has a distinctive rotting smell and goes on to invade surrounding material.
Once the environmental conditions are wet or humid occur and there is reduced oxygen, it increases rapidly between the temperatures of 8C to 30C, but rot increases dramatically when temperatures are over 20C.
Stems of infected plants typically have inky black symptoms on the outside which are the spores and the pith above the discolouration will be decayed and the leaves yellowed and wilt. In wet weather the decay is wet and slimy and may spread to most of the plant. Under dry conditions, infected tissue becomes dry and shrivelled, and the disease is often restricted to the underground portions of the stem.
One of thew most common bacteria is Erwinia carotovora and its various sub species like atroseptica, chrysanthemi and carotovora which is most the prevalent. These bacteria usually enters the plant via a wound or by various insects also by using pruning utensils that are infected.
There may well be other fungi and yeasts that are secondary invaders after the initial infection by the bacteria. Bacterial Black Stalk Erwinia sp. Picture by Howard F. Schwartz, Colorado State University,


Good husbandry and disease management is based primarily on sanitation and cultural practices.
In storage good ventilation helps to keep tubers cool and prevent the accumulation of CO2, which makes the oxygen levels fall, and eliminate moisture films all of which aids the germination of the bacteria spores.
Soft rot can be kept to a minimum if potatoes are kept dry.
Minimize mechanical damage to tubers during harvesting and handling.
Delaying harvest until the skin has set reduces tuber injuries. This will reduce the entry points for the pathogen. Remove damaged and rotting tubers and fruit from storage as soon as possible.
If soft rot has been a problem before plant small whole seed or make sure cut seeds are properly cured before planting. Avoid infected plant debris left rotting in the field.
Control nematodes and other insect pests that serve as vectors (carriers) of the bacteria to invade the plant tissues Remove infected plants immediately.
Practice crop rotation by using crops that are not susceptible to the bacterial soft rot disease like soybean, forage legumes, and small grains

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