Bacterial blight is a serious infestation affecting paddy crops. Initially water-soaked yellowish stripes appear on the leaf blades starting at the leaf tip, later increasing in length with a wavy margin.
On the leaf surface a milky or opaque dewdrop can be noticed during early morning time. Lesions turn yellow to white as the disease advances. Severely infested leaves tend to dry quickly.
Colour change
Lesions later turn grey in colour. As the infestation progresses the lesions cover the entire leaf blade which may turn white or straw coloured. Later the leaves wilt and roll up. Under severe conditions the entire crop wilts completely.
Presence of weeds, rice stubbles and ratoons of infected plants, presence of bacteria in the paddy seeds and irrigation canals, warm temperature, high humidity, water stagnation, and over fertilization favour the infestation spread.
In the field, a portion of the infested leaf can be cut and placed inside a test tube with water for a few minutes. The cut portion inside the tube can be observed against sunlight to see bacterial ooze streaming out from the cut end into the water. After an hour the water turns turbid.
Remove weeds, rice straws, ratoons to prevent infestation.
Likewise maintaining shallow water in the paddy nursery beds, providing good drainage during severe flooding, ploughing under rice stubble and straw following harvest are proper management practices to be followed.
Right application of fertilizers is recommended. Use resistant varieties such as Ajaya, Asha, CO-43, Gobind, Radha, Sujatha, Suraj, Swarna, Udaya varieties.
Seed soaking
Soaking the seeds before sowing in 0.1 gm/litre of streptocycline and 0.1gm/litre of copper sulphate solution for 20 minutes is the best practice to avoid spread of this infestation.
Apply nitrogen in three split doses, 50 per cent basal, 25 per cent during tillering phase and 25 per cent during panicle formation phase.
(Mallikarjun Kengal, assistant professor and V.R. Joshi, plant pathology, Extension education unit, University of Agricultural Sciences, Koppal- 583231, phone: 08539- 230205.)
