Bacterial Soft Rot of Cabbage

Soft rot of cabbage is caused by the bacterium Pectobacterium carotovorum, previously called Erwinia carotovora. It is a major problem during wet weather and can be more severe when plants lack sufficient calcium. The pathogen is generally spread by irrigation water, rain, several species of maggot flies and other insects.

Disease development is usually favoured by warm temperatures of 25 to 30°C, humid conditions or following periods of wet weather that lead to free moisture on plant tissues.

Symptoms:

1.    Cause the formation of water-soaked spots. These spots enlarge over time and become sunken and soft.

2.    Interior tissues beneath the spots become mushy and discoloured, with the discoloration ranging anywhere from cream to black.

3.    Seepage from affected areas.

4.    In severe cases of infection, leaves, stems and roots may decay entirely.

5.    A strong disagreeable odour from the rotten tissues.

6.    Breakdown of plant tissues.

Disease Management:

A) Chemical control method

An effective control bacterial soft rot can be achieved through prevention because once infection occurs, it cannot be cured, but the bacteria can be prevented from spreading.

Copper-based fungicides are recommended for use in preventing and suppressing the activity of the bacterial pathogen, and they include the following;

1.    GREENCOP 500WP

2.    TRINITY GOLD 452 WP

3.    COLONIZER 440 WP

4.    BIODISTINCTION XTRA 700CS

5.    PYRAMID 700WP - suppresses the activity of the bacterium within the crop.

6.    OPTIMIZER - boosts the crop’s immunity and manages stress.

B) Non-chemical control methods

1.    Set out plants in rows to allow good air drainage.

2.    Plant resistant cultivars.

3.    Use disease free and healthy planting materials.

4.    Cultivate carefully to minimize injuring plants.

5.    Control frequency and source of irrigation water.

6.    Avoid overhead irrigation to keep the foliage dry.

7.    If soft rot is a serious, recurring problem in the garden, do not grow susceptible crops in that area for a minimum of three years.

8.    Remove infected plants immediately and do not compost.

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