Bacterial Canker of Mango
Xanthomonas citri pv. mangiferaeindicaebacteria
Tiny, water-soaked lesions measuring 1-4 mm in diameter appear on leaves. They are slightly raised, angular formed or shaped star-like. They are light yellow in the early stages but later enlarge to become necrotic cankerous patches of dark brown color. As the disease progresses, the leaves turn yellow and fall off in severe cases. Branches, twigs and stems can display swollen lesions that later turn dark brown. They eventually crack, exposing the internal tissue and oozing gummy substances. Dark brown or black water soaked lesions may show on the fruits, often bursting and secreting contagious ooze. Sometimes, pulp and stone are affected, too. Fruit lesions and plant secretions attract insects and opportunistic pathogens which initiate rotting.
The disease is caused by a variety of the bacterium Xanthomonas citri. It enters the plant either through stomata on leaves and lenticels on twigs and fruits. The bacterium survives in infected parts on the tree (up to 8 months in leaves). Cankers on the twigs are the primary cause for further infection of fruits. Disease spread is rapid during rainy days, additionally enhanced by wind. Direct contact between trees or fruits also spreads the disease.
Sprays containing copper compounds (e.g. copper oxychloride 0.3%) applied on early shoots every 10-14 days have proven effective. Spraying biocontrol agents such as Acinetobacter baumannii on infected trees can also effectively reduce populations of X. citri.
Always consider an integrated approach with preventive measures together with biological treatments if available. Two sprays of streptocycline (0.2-0.3ml/1l water) at 20 days intervals reduce fruit infection. Dipping the fruits in a solution of agrimycin-100 (0.2ml/1l water) is effective as well. Injecting bavistin (1000 ppm) followed by plantomycin (200 ppm) into the stems of infected trees might also work.