Causal Agent: 

Bacteria (Pseudomonas syringae pv. phaseolicola)

Characteristic Symptoms:
 
Initial symptoms on leaves are small, angular and water-soaked spots.
   
Enlarged spots are surrounded with the characteristic halo of yellow tissues.
   
Spots on pods are oval, water-soaked, reddish-brown and slightly sunken.  As pods mature, they turn yellow to tan but the spots/lesions remain green and may exhibit bacterial ooze on the surface.
   
Conditions for Disease Development:
 
Halo blight is favoured by humid conditions and cool to moderate temperatures (18-22°C).
   
The bacterium is spread by water splashes, rain, farm implements, humans and contact between adjacent leaves wet from irrigation, rain or dew.
   
The bacterium can survive in infected plant tissues for up to 1 year.
   
Management and Control:
 
Use pathogen-free seeds.
   
Crop rotation with non-host plant for at least two years to reduce the inoculum level in the soil.
   
Remove weeds, volunteer beans and plant debris that serve as alternate hosts for the bacterium.
   

Avoid overhead irrigation
   
Use resistant varieties, if available.
   
Preventive application of copper-based fungicides (e.g. Cupravit®, Super Blue, Vitigran blue, Funguran, Kocide, Hydroxide super).  
   
 
   

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