Common Blight

(Xanthomonas axonopodis pv. phaseoli)

Credits: Biovision-Infonet

This disease is a constraint to bean production in Kenya. Crop losses of between 10 and 75% have been reported. The common blight produces similar symptoms on leaves, pods, stems and seeds. Small water-soaked spots are the first symptoms observed on leaves and appear within 4 to 10 days of infection. As the spots develop, the centre becomes dry and brown. The lesion is surrounded by a narrow band of bright yellow tissue. However, yellowed tissue is occasionally absent.What to do:

• Intercropping bean with maize was shown to reduce the severity of common bacterial blight during 1987-88 in Tanzania.
• Use certified disease-free seed.
• Plant resistant varieties (e.g. French bean variety ‘Paulista’).
• Plough under bean debris after harvest.
• Practise a 2-3 year crop rotation without legumes.
• Do not work in bean fields when the plants are wet.
• If blight is observed on scattered plants, spot application of copper hydroxide could be considered.