Xanthomonas citri pv. mangiferaeindicae
The main symptoms of bacterial black spot of mango appear on leaves and fruits but twigs and branches may also be affected in severe cases. Initially, small black and water-soaked lesions occur on the leaves. These spots are surrounded by chlorotic margins and limited by the veins. As the disease progresses, the spots dry up and leaves can shed, leading to defoliation. In the early stages, water-soaked, light spots appear on infected fruits. Later, they evolve into dark star-shaped craters, oozing infectious gum that attracts opportunistic pathogens. Light infection causes decreased fruit quality whereas severely infected fruits might fall off. Lesions can appear resulting in black and cracked branches and stems, which in turn may weaken the stability of the tree.
The disease is caused by a strain of the bacteria Xanthomonas citri. It can survive up to 8 months in living tissues. It infects trees through wounds and natural openings. The pathogens can spread from tree to tree or between fields by wind-driven rain or through implements used for management activities such as pruning. Alternatively, the spreading occurs via infected plant material or through contact in the case of fruits. The most favorable temperature for an infection with bacterial black spot is between 25 and 30 °C. High humidity also fosters infections. Windbreaks or the planting of tree species with dense foliage around the orchard can reduce the spreading of the disease.
Regular spraying with products containing copper oxychloride has proven effective in preventing and decimating infections. Biocontrol agents such as Acinetobacter baumannii on infected trees can also effectively reduce population of X. citri.
Always consider an integrated approach with preventive measures together with biological treatments if available. Sprays containing thiophanate-methyl or benzimidazole can be applied to control bacterial black spot of mango.