Causal Agent:
Bacteria (Xanthomonas campestris pv. phaseoli)
| Characteristic Symptoms: | |
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Leaf symptoms start as water-soaked spots that enlarge, become flaccid and necrotic with lemon yellow border. |
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Lesions are found along leaf margins and interveinal areas of the leaves and as they enlarge and coalesce, plants have burn-like appearance. |
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Spots on pods are dark red-brown, water-soaked, circular and slightly sunken. |
| Conditions for Disease Development: | |
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Warm temperatures (28-32°C) and high relative humidity favour disease development. |
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The bacterium can be spread to other plants/fields by windblown rain, soil, and plant debris, contact between wet leaves, irrigation water, insects like whiteflies and leafminers, farm implements and humans. |
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The bacterium can overwinter in seed and infested bean straw and can survive for long periods of time. |
| 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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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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