Introduction

Rice blast disease is one of the key threats to rice production and is attributed to the fungal pathogen Pyricularia oryzae. The disease can lead to considerable yield loss and places a substantial burden on the economy as well as food security with respect to rice-growing regions, particularly countries like India, China, and Bangladesh. Rice blast disease is the most destructive among all rice diseases, attacking 10% to 30% of rice annually harvested. This loss can feed 60 million people. The forms of losses and their impacts need to be understood and managed to reduce the loss.

Characteristics of rice blast and its impact on yields.

Rice blast is caused by a fungus that attacks the rice plant at several points—the leaves, the stem, and the panicle. It shows early signs such as white or grey-green spots with brown edges on the leaves, which may grow into larger lesions. In extreme cases, it attacks the nodes of the stem, leading to the breaking of the stem. Grey-brown spots may bleach the panicles, which can even fall down. If it happens before grain formation, then it results in low-quality grains or no grain formation. The size and shape of spots differ with rice varieties. The three main types of blasts include:

Leaf Blast: The whole crop appears to be scorched or burnt. This is why it is called "Blast." Even after grain formation, the whole crop may shed in extreme cases of the infection. These lesions are oval or diamond-shaped with pointed ends and have a greyish or white center. They can be up to 2 cm long on flowering plants and have dark green or reddish-brown margins. The lesions start as small white, grey, or blue-tinged spots and enlarge quickly in moist conditions.

Neck Blast: It turns black and dry at the neck of the panicle and prevents the proper development of grain. The panicle might break at the neck and droop downwards.

Nodal Blast: The nodes or joints of the stems turn black and split apart eventually at this stage.

Economic consequences of blast disease

The economic impact of rice blast disease affects food security and livelihoods for millions. As rice production cannot keep pace with the increasing demand, communities dependent on it are seriously affected.

1.Population Growth Impact on Land and Water Resources The rate at which the world is growing in terms of population has added to the need for land and water for human use. Climate change, particularly extreme weather events, has compounded this problem by shrinking land resources for farming, particularly rice. According to FAO estimates, food production must increase by 70% in order to produce enough food for the 9 billion people projected in the world by the year 2050.

2.Rice Production and Food Security Over 200 million families rely on it as an important crop, providing employment and income. It is the primary food source for some 2.5 to 3.5 billion people worldwide in poor countries; the daily diet comes to an average of more than 500 calories. Improvements in rice production have not yet met demand. While in 2008, the production was able to yield 480 to 685 million tonnes, an additional 140 million tonnes were required by the year 2020. Since 2000, production has been less than consumption, and it is projected to continue increasing by 2030.

Yield Loss per Acre

The yield loss per acre may be hard to predict since this is highly dependent on the level of seriousness of the disease and the type of rice variety being grown. Losses can also vary with environmental conditions. On average, 10% to 30% of loss occurs due to yields attributable to blast disease. However, in infestation-prone areas, it may reach up to 70%. A serious neck blast outbreak in India averaged a yield reduction of around 35% per acre.

Best farming practices to prevent and control rice blast

1.Conventional Practices: Rice blast can be controlled through the cleanliness of the fields by cleaning up the residues, crop rotation, and summer ploughing. Rice plantings should not be too close, nor should they be over-nitrogenated since both tend to make the field too propitious for the fungus; timely weeding cuts down on the threats of the disease since there is a lesser chance for the fungus to have hosts.

2.Irrigation Management: Flooded fields prevent rice blasts due to the fact that deeper flooding (at least 4 inches) conditions are unfavorable to the fungus's ability to advance. Consistent water levels not only avoid the onset of disease but also promote healthier root systems in rice plants.

3.Time of Planting: Early planting within a tropical region's rainy season can ensure crops avoid early infection by the blast. Such timing will facilitate exploiting beneficial weather conditions to reduce the chances of disease outbreaks at critical stages of growth.

Effective Chemicals for Controlling Paddy Blast

Several chemical molecules have been developed that are targeted against the blast pathogen for effective management of the disease. Among the prominent fungicides that gave good results are:

1.Kasugamycin: Kasugamycin is a broad-spectrum antibiotic fungicide used primarily in agriculture to control fungal diseases in various crops. Kasugamycin works by inhibiting protein synthesis in fungi. This disruption prevents fungal growth and reproduction, effectively controlling fungal pathogens. It controls leaf blast, nodal blast, and neck blast. Biomycin is the well-known brand in the segment. It is primarily used to control fungal diseases such as rice blast, damping off, and leaf spot diseases in crops like rice, tomatoes, peppers, and cucumbers.

2.Tricyclazole: This is a systemic fungicide, a protectant fungicide that prevents the fungus from penetrating the plant. Due to MRL issues, Tricyclazole has restricted sale on Basmati paddy.

Conclusion

Rice blast disease remains one of the dominant global issues in rice production, causing yield losses that impinge on food security and livelihoods for millions of people. The effects of this disease can be minimized through proper estimation methods, cultural practices, and effective chemical control. Companies like Biostadt, with their focus on agricultural innovation and crop protection solutions, are playing a pivotal role in combating such challenges. Research activities in this area were characterized by promising, though preliminary, evidence on disease-resistant rice varieties and improved management techniques. These will be crucial components toward securing future rice production.