Citrus canker

Citrus canker
    Causal organism: Xanthomonas campestris pv.citri
    Symptoms
    • Leaves: Initially water soaked patches appear which slowly turn brown and produce corky raised spots which leads to yellow hallow.
    • Stem: Same as on leaves but yellow hallow is absent, bark eruption takes place and, we can see bacteria oozing out during warm rainy season from cracks.
    • Fruits: Brownish corky out growth with cracks and crater like appearance at a later stage is the common symptom. Fruit size is reduced and marketing quality deteriorates.
    • Fruit rottening is common when stored.
    Etiology
    • Canker-infected leaves and twigs serve as the source of inoculum to spread the disease from season to season.
    • However, the cankered leaves drop early and bacteria perish rapidly in the soil.
    • Primary source of inoculum: infected plant and soil
    • Secondary source of inoculum: Bacterial cells spread through Irrigation water, agricultural implements, pruning shears etc.
    Epidemiology
    • Prevalence of 20o-35oC temperature, high humidity ( %) and the presence of moisture on the host surface favour the disease.
    Life cycle
    • The bacterium enters the host through stomata or wounds.
    • It multiplies in the intercellular space, dissolves the middle lamella and get established in the cortex region.
    • Canker pustules develop an exude bacteria in the form of gummy substance.
    • They are freely disseminated, chiefly by wind.
    • Citrus leaf-minor helps dissemination and infection of citrus canker.
    • Leaves affected by minor and canker get distorted and drop early.
    • The injury in the leaf epidermis made by the burrowings of leaf-minor serve as an easy opening to the canker bacterium and the canker lesions appear through out the leaf in zig zag manner.
    Management
    • Quarantine: If area is disease free, restrict the entry of planting material from infected to healthy area.
    • Cultural: Infected leaves, stem, fruit etc should be removed and burnt. Bordeaux paste should be applied at the cut end portions of stem.
    • Hot water treatment of root stocks at 50°C for 10-15 minutes.
    • Biological: Pseudomonas fluorescens suspension can be sprayed as biological control agent.
    • Chemicals:1% Bordeaux mixture or
    • 0.3%Copper Oxychloride or
    • 500 ppm Streptocycline should be sprayed on the plant

Last modified: Friday, 20 January 2012, 1:28 PM