Bacterial blight disease:
Causal organism: Xanthomonas Oryza.
Symptoms:
Following the different stages symptoms of bacterial blight disease in rice plant
a. On seedling-
· initially leaves turn greyish green and roll up later on leaves turn yellow to straw colour.
· Finally leaves die leading to witting / death of seedling.
· The symptoms of seedlings may be confused with early rice stem bore attack to distinguish it from rice borer attack-:
a. Cut the seedlings from base and squeeze the lower end between fingers it will drop out yellow coloured bacterial ooze drop.
b. Unlike stem borer attack, seedling attack by bacterial blight can be easily pulled out of the soil.
b. Symptoms in old plants-
· Leaves show water soaked to yellow-coloured strips on leaf blade or leaf margin or on mechanically injured parts, these strips have wavy margins.
· Lter on these strips extend towards the base of the leaf (deaf sheath).
· Bacterial oozes can be seen as milky dew drops specially in the early morning on young leaves.
· Later on, leaves turn yellow to greyish white and bacterial oozes on these leaves dry up and appears as beads under the upper layer of leaves.
· On older lesions greyish white leaves develops black colored dots.
· These dots are growth of saprophytic fungi on dead tissue.
Identification:
Following some step to identification the rice disease:
· Cut the lesion
· Dip it in a container of having clear water.
· Observe to under the light.
· Thick fluid coming out the lesion will be observed it will make.
Favourable condition:
· Temperature: 25-34 degree.
· Relative humidity: more than 70%
· Less dose of nitrogen recommended fertilizer.
Disease cycle:
Perennation:
· Through weeds and plant debris and seeds.
Primary infection:
· From weed host, plant debris and seeds.
Secondary infection:
· Through the spread of bacterial oozes with the help of irrigation H2O from 1 plant to another plant.
Diagram of bacterial blight disease cycle:
Management:
Cultural method
· Careful handling of seedling during transplanting.
· Maintaining shallow water in nurseries.
· Providing good drainage during severe flooding.
· Reducing the amount of inoculum through clean cultivation and drying the fallow fields.
· Removing collateral weed hosts from bunds and channels.
· Using only disease-free seedlings.
· Grow resistant cultivars IR 20 and TKM 6.
· Planting resistant cultivars.
· Practicing good sanitation by removing weeds and plowing under stubble and other rice detritus.
· Allowing fields to dry between plantings.
Chemical method
· Using seed treatment with blenching powder and zinc sulphate.
· Limiting and balancing the amount of nitrogen fertilizer.
· Spray Streptomycin sulphate and tetracycline combination 300g + Copper Oxychloride 1.25kg/ha.
Biological method
· Use of bacterial antagonists of pathogens to reduce bacterial blight, through their use has been limited.
