Rice is one of the most important crops in the world, feeding more than half of the global population. However, rice production is threatened by various diseases, among which bacterial blight of rice is one of the most devastating.

It can cause up to 70% yield loss, affecting the food security and livelihoods of millions of rice farmers and consumers. In this blog post, we will learn about the symptoms, causes, and management of bacterial blight of rice and how to prevent and control this disease effectively.

Bacterial blight of rice is a severe disease that affects rice production worldwide. It is caused by a bacterium called Xanthomonas oryzae pv. oryzae infects the rice plant’s vascular system and causes wilting, yellowing, and drying of the leaves.

Symptoms of Bacterial Blight Disease:

The symptoms of bacterial blight of rice vary depending on the stage of the plant and the environmental conditions. The disease can affect seedlings, tillers, leaves, panicles, and grains.

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1. On seedlings, the disease causes water-soaked lesions on the leaf margins, which later turn grayish-white and dry up. The infected seedlings may die or produce stunted plants.
2. On tillers, the disease causes the base of the stem to turn brown and rot, resulting in the collapse of the whole plant. This symptom is known as kresek.
3. On leaves, the disease causes narrow, translucent streaks along the leaf veins, which later turn yellow and then brown. The streaks may coalesce and cover the entire leaf blade, causing it to dry up and fall off. This symptom is known as leaf blight.
4. On panicles, the disease causes the neck of the panicle to turn brown and break, resulting in the failure of grain filling. This symptom is known as panicle blight or rotten neck.
5. On grains, the disease causes the grains to turn white or gray, with dark brown spots or streaks. The infected grains may fade or crack, reducing the quality and yield of the rice.

The disease can be diagnosed by squeezing the infected parts of the plant and observing the bacterial ooze that comes out. The ooze is a sticky, milky-white liquid that contains millions of bacteria.

Causes of Bacterial Blight of Rice

The bacterium that causes bacterial blight of rice survives in the soil, water, plant debris, seeds, and weeds. It can spread by rain, wind, irrigation, insects, birds, animals, farm tools, and human activities.

The disease is favored by high temperature, high humidity, and high nitrogen levels in the soil. The disease is more severe in the rainy season and flooded fields.

History of Bacterial Blight of Rice

Bacterial blight of rice was first reported in Japan in 1884. Since then, it has been found in many rice-growing regions, such as Asia, Africa, America, and Australia.

The disease has caused significant losses in rice production and quality, especially in Asia, where rice is a staple food for millions. The disease has also posed a threat to global food security and the livelihoods of rice farmers.

Some of the major outbreaks of bacterial blight of rice in history are:

• In 1971, the disease caused a 15% yield loss in Indonesia, affecting 1.5 million hectares of rice fields.
• In 1976, the disease caused a 50% yield loss in the Philippines, affecting 0.5 million hectares of rice fields.
• In 1986, the disease caused a 30% yield loss in India, affecting 6 million hectares of rice fields.
• In 1990, the disease caused a 20% yield loss in China, affecting 3.3 million hectares of rice fields.
• In 1995, the disease caused a 10% yield loss in Bangladesh, affecting 1.2 million hectares of rice fields.

Management of Bacterial Blight of Rice

The management of bacterial blight of rice involves the use of integrated pest management (IPM) strategies, such as:

• Planting resistant rice varieties can reduce disease incidence and severity by 50-90%. Some resistant varieties are IRBB21, IRBB60, IRBB65, IRBB67, and IRBB71.
• Use certified seeds or treat seeds with hot water or chemicals to kill the bacteria on the seed surface.
• To reduce the sources of inoculum and break the disease cycle, farmers can practice crop rotation, intercropping, or fallowing.
• Avoiding excessive use of nitrogen fertilizer can increase the susceptibility of the plants to the disease.
• Controlling weeds, insects, and rodents, which can harbor or transmit the bacteria.
• Using biological control agents, such as Bacillus subtilis, Pseudomonas fluorescens, and Trichoderma harzianum, can inhibit the growth and activity of the bacteria.
• Chemical control agents, such as copper compounds, antibiotics, or plant extracts, can reduce the disease severity by 10-40%. However, these agents should be used cautiously, as they may negatively affect the environment and human health.

Bacterial blight of rice is a challenging disease that requires constant monitoring and management. By following the IPM strategies, rice farmers can minimize the losses caused by the disease and ensure sustainable and profitable rice production.

Conclusion

The bacterium that infects rice plants’ vascular system can cause several symptoms, including wilting, yellowing, and drying of the leaves, and can lead to a failure in grain filling. These symptoms pose a significant threat to rice production and global food security.

Fortunately, practical strategies to control the disease include using resistant varieties, certified seeds, crop rotation, biological and chemical control agents, and other IPM techniques. By adopting these measures, rice farmers can protect their crops from bacterial blight, improve their productivity, and increase their income.

Info Source / References:

1. Rice Knowledge Bank, International Rice Research Institute(IRRI).
2. Bangladesh Rice Research Institute(BRRI).

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I am Gaushoul Agam

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ToAgriculture

I am an experienced Horticulture Officer in the Department of Agricultural Extension in Bangladesh. I am committed to improving agriculture and farming.

I created ToAgriculture to address global food safety concerns. These concerns are caused by a growing population, diminishing farmland, and the impact of climate change on agriculture. I assist readers in learning modern farming techniques.

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