Causal Agent:
Bacteria (Pseudomonas syringae pv. phaseolicola)
| Characteristic Symptoms: | ||
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Initial symptoms on leaves are small, angular and water-soaked spots. | |
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Enlarged spots are surrounded with the characteristic halo of yellow tissues. | |
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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: | ||
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Halo blight is favoured by humid conditions and cool to moderate temperatures (18-22°C). | |
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The bacterium is spread by water splashes, rain, farm implements, humans and contact between adjacent leaves wet from irrigation, rain or dew.
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The bacterium can survive in infected plant tissues for up to 1 year. | |
| Management and Control: | ||
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Use pathogen-free seeds.
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Crop rotation with non-host plant for at least two years to reduce the inoculum level in the soil. | |
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Remove weeds, volunteer beans and plant debris that serve as alternate hosts for the bacterium.
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Avoid overhead irrigation |
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Use resistant varieties, if available. | |
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Preventive application of copper-based fungicides (e.g. Cupravit®, Super Blue, Vitigran blue, Funguran, Kocide, Hydroxide super). | |
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