UNDERSTANDING AND MANAGING RICE BLAST

Rice is one of the most vital staple foods worldwide, but its cultivation is often threatened by various diseases. One such disease is Rice Blast, caused by the fungus Magnaporthe oryzae. This blog aims to provide farmers with essential insights into identifying, understanding, and effectively managing rice blast.

Leaf Blast                                Nodal Blast

Neck Blast

What is Rice Blast?

Rice blast is a fungal disease that affects all aboveground parts of the rice plant, including leaves, leaf collars, culms, necks, and panicles. The initial symptoms include white to grey-green lesions with brown borders. As the disease progresses, small specks on the leaves enlarge into spindle-shaped spots measuring 0.5 to 1.5 cm in length and 0.3 to 0.5 cm in width, characterized by ashy centres.

Older lesions can become elliptical or spindle-shaped, whitish to gray in color, with necrotic borders. These spots often coalesce to form large, irregular patches. In severe cases, the entire crop may exhibit a blasted or burnt appearance, which is how the disease gets its name.

Types of Blast

Rice blast occur in different forms:

• Leaf Blast: Spindle-shaped lesions with a grey centre and brown margins appear on the leaves.
• Neck Blast: The neck region of the panicle turns black and shrivels, inhibiting grain set and causing the panicle to break. If infection occurs before the milk stage, no grains form.
• Nodal Blast: Nodes turn black and can break, further compromising the plant's integrity

Identification of Pathogen Causing Rice Blast

The disease is caused by the fungus Magnaporthe oryzae, which can survive in rice seeds and infected stubble. The spores of this fungus can spread over long distances via wind, leading to new infections during subsequent growing seasons. The conidia, or reproductive spores, are typically pear-shaped (pyriform) and measure 20-22 x 10-12 µm.

Symptoms of Blast of Rice

Rice Blast affects crops from seedling to ear-heading stages, with symptoms appearing on leaves, nodes, rachis, and glumes.

• Leaf Blast: Small bluish-green flecks on leaves enlarge into spindle-shaped spots with grey centres and dark brown margins. These spots coalesce, drying large leaf areas, and may also appear on the sheath. Severely infected fields look burnt.
• Nodal Blast: Black lesions girdle nodes, causing them to break and resulting in plant death above the infected node.
• Inter-nodal Infection: Infection at the plant base leads to "white panicles," similar to yellow stem borer or water stress symptoms.
• Neck Blast: Grayish-brown lesions girdle the neck, causing panicles to droop. Early infections stop grain formation; later infections lead to poor-quality grains.
• Panicle and Spikelet Infections: Brown lesions appear on panicle branches and spikelet pedicels, affecting grain quality.

Lesion size and shape vary by rice variety, but early identification is key to effective management.

Favourable Conditions for Blast of Rice

Several environmental conditions favour the development of rice blast:

• Humidity: High relative humidity (90% and above) and wet leaves.
• Temperature: Optimal growth occurs between 25-28°C.
• Weather: Cloudy skies and frequent rainfall.
• Soil Fertility: High nitrogen levels, particularly from ammonium sulfate, promote the ṁdisease

Management of Rice Blast of Rice

Cultural Methods

1. Resistant Varieties: The most effective way to manage rice blast is to plant resistant varieties. Some recommended resistant varieties include CO 47, CO 50, ADT 36, IR-64, and many more.
2. Fertilizer Management: Avoid excessive nitrogen application. Nitrogen should be applied in three split doses to minimize the risk of blast.
3. Weed Control: Remove weed hosts from bunds to reduce the spread of the fungus.

Preventive Measures

1. Nursery Management: Avoid dry nurseries and late planting. Stagnate water to a depth of 2.5 cm in the nursery and soak seedlings in a solution of Pseudomonas fluorescens to enhance resistance.
2. Sanitation: Burn straw and stubbles after harvest to eliminate potential sources of the fungus.
3. Disease Monitoring: Regularly monitor crops for early signs of infection and act swiftly.

Chemical Control

While cultural and preventive measures are critical, fungicides can play a vital role in managing rice blast:

Katyayani Azozole is one of the best fungicides for controlling fungal diseases like Rice Blast, Sheath Blight of Rice, Early Blight, Late Blight, Downy Mildew, Rust, Leaf Spot, Red Rot, and Smut. Formulated for powerful protection.

Conclusion

Rice blast disease poses a significant threat to rice cultivation, but with the right management strategies,and the use of effective fungicides like Azozole, farmers can safeguard their crops against this destructive disease. By staying informed and proactive, farmers can ensure a healthy rice yield and contribute to global food security.

For more information on how Azozole can help you control Blast of Rice, visit our website Krishi Seva Kendra or contact us today! Together, we can work towards a healthier future for rice cultivation.

FAQs related to Blast of Rice

Q. What is Rice Blast?

A. Rice Blast is a fungal disease caused by Magnaporthe oryzae, affecting all aboveground parts of the rice plant.

Q. What are the main symptoms of Rice Blast?

A. Symptoms include white to grey-green lesions with brown borders, spindle-shaped spots, and a burnt appearance of the crop.

Q. What are the types of Rice Blast?

A. Rice Blast occurs as Leaf Blast, Neck Blast, and Nodal Blast, affecting different parts of the plant.

Q. How does Rice Blast spread?

A. The fungus spreads through spores carried by wind and survives in rice seeds and infected stubble.

Q. What conditions favour Rice Blast development?

A. High humidity (90%+), temperatures between 25-28°C, cloudy weather, and high nitrogen levels promote the disease.

Q. Which is the best fungicide for the control Rice Blast?

A. Katyayani Azozole is one of the best recommended fungicide for the control of Blast disease of Rice