Bacterial Leaf Streak (BLS) of rice

Causal Organism : Xanthomonas oryzae pv. oryzicola

Bacterial Leaf Streak The disease is usually observed during the tillering stage of the rice crop.The   rice plant can easily recover at the later growth stages and grain yield losses are minimal. Bacterial leaf streak is widely distributed in Taiwan, southern China, Southeast Asian countries, India, and West Africa. The disease is not reported to occur in temperate countries including Japan. Losses as high as 32.3% in 1000-grain weight due to BLS were reported.

Symptoms

Bacterial Leaf Streak first appears as short, water-soaked streaks between the veins, which become longer and translucent and turn to light brown or yellowish brown. Thus, large areas of the leaf may become dry due to numerous streaks. At the later stage the disease is indistinguishable from the bacterial leaf blight. The linear streaks or narrow transparent streak can be seen against the sunlight. When the advancing part of the streaks are cut and placed in a glass with water, mass of bacterial cells would be seen coming out from the leaf making the water turbid after 5 minutes. Browning and drying of leaves also occur and lesions turn brown to grayish white then dry browning and drying of entire leaves. . Reduced 1000-grain weight under severe conditions.

Management

• The disease can be managed by proper application of fertilizers and proper planting spacing, the use of resistant varieties, and hot water treated seeds.
• Practicing field sanitation is important. Ratoons, straws and volunteer seedlings left after harvest can be destroyed to minimize the initial inoculums at the beginning of the season. Providing good drainage system especially in seedbeds can also manage this disease.
• Planting of resistant varieties, which are available at IRRI and at National Research Institute, is the most effective method of controlling bacterial leaf streak. Fallow field and allowing drying thoroughly is also recommended.