Xanthomonas axonopodis pv. punicae
The symptoms first appear after 2-3 days of infection. Yellowish water-soaked circular spots can be found on the plant parts. Premature defoliation occurs in severe cases. The circular spots appear as irregular lesions during later stages. Gradually, the center of the spots become necrotic and turns dark brown. The pathogen also causes girdling and crackling of the stems and branches. In advanced stages of infection, tissue necrosis occurs on the leaves and twigs. The disease causes the entire fruit to crack open, eventually turning the whole fruit dark and dry. Plants are susceptible during all growth stages.
Damage is caused by the airborne bacterium Xanthomonas axonopodis pv. Punicae. The pathogen infects a broad range of cultivated varieties irrespective of their growth stage. The bacteria enter through natural openings and wounds. The bacteria overwinter in infected plant leaves, stems and fruits. Rain splash, insects and contaminated pruning tools aids in spreading the diseases locally. Higher day temperature and low humidity favor pathogen growth. The optimal temperature for growth of bacterium is 30°C. Rain and spray splashes, irrigation water, pruning tools, humans and insect vectors are responsible for the secondary spread of the bacteria. The disease reduces the marketing potential of the fruits.
Apply Biocontrol agents like Bacillus subtilis, Pseudomonas fluorescence and Trichoderma harzianum. Soak Neem leaves in cow urine and spray in order to control pests and plant pathogen. Apply 40% of Tulsi leaf extract followed by Neem seed oil. Also, apply an extract of Garlic bulb, Meswak stem and Patchouli leaves at 30% per concentration.
Always consider an integrated approach with preventive measures together with biological treatments, if available. No effective chemical control for this disease has been discovered yet. Several management options involving the application of antibiotics, chemicals and other cultural treatments have been considered, but chemical treatments are only less effective. Chemicals like Bordeaux mixture, Captan, copper hydroxide, bromopol, and antibiotic streptocycline can be used alone or in combinations.