Causal Agent: 

Fungus (Collectotrichum higginsianum)

Characteristic Symptoms:
 

Affects leaves, petioles and stem.
   
Lesions on leaves are circular to irregular, small, dry and pale gray.
   
Under favourable conditions, lesions coalesce forming irregular large spots.
   
Severe infection leads to yellowing of leaves and wilting.
   
Symptoms on petioles and stem include elongated, sunken, gray to brown lesions with black border.
   
Conditions for Disease Development
 
The pathogen can survive on plant debris, volunteer plants and related weeds.
   
Temperature range of 25-30°C,  wet conditions and high relative humidity favor disease development.
   
Management and Control:
 
Maintain good field sanitation, remove infected plants/plant parts and dispose properly.
   
Crop rotation with non-host crop for at least 3 years to reduce the amount of primary inoculum. 
   
Remove volunteer and weedy crucifers that may serve as alternate hosts for the pathogen.
   

Spray with copper-based fungicides (e.g. Cupravit®, Vitigran Blue®, Nordox 50®), Mancozeb (Dithane M-45®) or Chlorothalonil (Daconil 2787®) at the initial onset of the disease.
   
   

References

Compendium of Brassica Diseases by APS (2007)

To view other diseases,  click here.

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