Causal Agent: 

Fungus (Phoma lingam)

Characteristic Symptoms:

Affects leaves, stem, root, seed stalks and pods.

Lesions on leaves are round or irregular in shape confined by the leaf veins which become necrotic and grayish often with dark margin as they mature.
Black, pinpoint pycnidia that exude pink spore mass under favourable moisture and temperature are produced on the affected areas.
Initial symptom on stem includes blackened xylem.  Severe infection causes brown to gray stem base discoloration and crown malformation.
Affected roots have brown or black dry rot with transverse-split tissue.
Conditions for Disease Development
Temperature range of 5-20°C and high relative humidity favor disease development.
The pathogen can survive on infected plant debris and on the soil and are spread by wind, rain splashes and runoff water.
Older plants are more susceptible that the younger ones.
Management and Control:
Use disease-free seeds
Use resistant varieties, if available.
Maintain good field sanitation, remove infected plants/plant parts and bury them to prevent release of conidia.
Crop rotation with non-host crop for 3-4 years to reduce the amount of primary inoculum. 
Flooding for 6-10 days can eliminate or reduce the pathogen in the soil and plant debris.
Remove volunteer and weedy crucifers that may serve as alternate hosts for the pathogen.
Apply fungicides such as metalaxyl+mancozeb (e.g. Ridomil Gold MZ 68 WGⓇ, Apron XL 350 ESⓇ), difenoconazole (e.g. ScoreⓇ, MontanaⓇ, PursueⓇ, BashⓇ), fosetyl aluminum (e.g. AlietteⓇ), Mancozeb (Dithane M-45®) or Chlorothalonil (Daconil 2787®) at the initial onset of the disease.

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