priyanshi.pptx blast disease of rice jaipur national

Blast disease of rice

1. JAIPUR NATIONAL UNIVERSITY SCHOOL OF AGRICULTURE SCIENCE Subject – Diseases of Field and Horticultural Crops and Their Management
Subject code – BSCAGCO504T22
Topic – Blast disease of Rice
Presented by – Priyanshi sharma (R50129)
Presented to – Dr. S. K. Khatik

2. Causal organism It is a fungus that causes the blast disease in rice.
It belongs to the group Ascomycetes (sac fungi).
It produces spores (called conidia) that spread through wind, rain, or irrigation water.
These spores germinate on the leaf surface and infect the plant

3. Symptoms of rice blast disease

4. Leaf blast The first symptom appears on leaves.
The center of the spots becomes gray or whitish, while the edges turn brown or dark brown.
When many spots join together, the leaf becomes dry and dead.
Severe infection looks like the leaf has been burnt .

5. Neck Blast The neck region, just below the panicle (ear head), becomes black or dark brown.
The panicle may bend down or break off.
Grains become unfilled or empty, and yield is greatly reduced.
This is the most serious and destructive stage of the disease.

6. Node blast Small, oval to spindle-shaped lesions appear on the nodes (stem parts)near the panicle.
The neck (uppermost node) is most affected.
Infected nodes turn grayish and rot, causing panicle neck breakage.
Leads to empty grains or shriveled panicles.

7. Collar blast Gray or brown lesions appear at the leaf-sheath junction.
The affected collar weakens, causing the leaf to wilt or dry.
Young seedlings may die completely if the infection is severe.
In older plants, it may reduce tillering and growth.

8. Favorable condition The fungus grows best at 25-30°C.
It does not grow well below 20°C or above 35°C.
Warm days and cool nights encourage infections
High relative humidity (above 90%) is ideal for the fungus.
Dew or fog on leaves provides moisture for spore germination.
Continuous leaf wetness for 10 hours or more helps infection.

9. Disease Cycle Primary Inoculum : Survives as mycelium or conidia on crop residues, weeds, or seeds. Dissemination : Airborne conidia spread via wind and rain splashes. Infection : Spores germinate and penetrate host tissue through appressoria . Secondary Spread : Repeated conidial production leads to rapid disease buildup under favorable conditions (high humidity, temperatures of 25-28°C, prolonged leaf wetness).

10. Management of rice blast disease A.Cultural Control:
Use of resistant varieties.
Avoid excessive nitrogen application.
Proper plant spacing and water management.
Crop rotation and destruction of infected debris. B. Biological Control:
Use of antagonistic fungi like Trichoderma spp.
Application of plant growth-promoting rhizobacteria (PGPR).

11. C. Chemical Control:
Seed treatment with fungicides (e.g., carbendazim ).
Foliar sprays with systemic fungicides (e.g., tricyclazole , azoxystrobin ) at early symptom stages.

D. Integrated Disease Management (IDM):
Combines resistant varieties, judicious fungicide use, and good agronomic practices for sustainable control .

12. Thank you...