Decaying or dying or wilting of plant leaves, flowers, fruits and stem tissue is called blight. Blight disease of rice is called leaf burn disease or collapse disease. Farmers in Japan were the first to discover the disease. In Japan, this disease is known as white rice disease. In Bangladesh in 1986, the existence of this disease was detected in Ropa Aman rice. In 1908, Japanese scientist Takaeshi proved that it is a bacterial disease. This disease reduces rice production by 22,000-110,000 tons per year in Japan.
Cause of rice blight disease: Xanthomonas oryzae is a bacterium called leaf blight disease of rice.
It is a rod-shaped bacterium. They are gram negative bacteria. They do not produce spores. Their cells do not have capsules. They have only one flagellum.
Infection or spread of rice leaf blight disease
1. In favorable conditions, the spores of this bacteria survive in the soil for many days.
2. The disease attacks the next crop through rice weed and weed. Subsists on grasses and wild rice as alternative feeders.
3. Bacterial spores can survive in canal water during summer.
4. Bacteria enter the host through plant wounds and hydathodes. Later enters leaf veins.
5. This germ spreads with the help of wind and rain water.
6. This germ spread in the field through ground water.
7. High temperature (25-30°C), high water vapor and rainfall are conducive to disease transmission.
8. The disease is spread by air flow and excess nitrogen in the soil.
Rice Leaf Blight Disease Symptoms: Rice leaf blight disease symptoms appear 5-6 weeks after infection. The symptoms are:
1. Disease symptoms on rice leaves
(i) In the initial stage, wet, semi-transparent and elongated spots are formed on the leaves.
(ii) Wet spots 5-10 mm long are seen on petioles, main veins and margins.
(iii) The spots coalesce to form white or yellow striped spots.
(iv) The spots become progressively yellow and gray and become large in size. It is called Kresek.
(v) Diseased leaves gradually dry up and curl up.
(vi) Affected areas appear wavy.
(vii) White sticky sap accumulates on the leaves.
(viii) Milk-colored sticky droplets accumulate on the leaves in the early morning and later dry up to form small orange beads.
(ix) Diseased leaves dry up quickly and plants die.
2. Disease symptoms in rice seeds
(i) Attack of the disease occurs at the time of emergence of the rice grain.
(ii) The glume of paddy becomes scorched by water retention and becomes straw-like in colour.
(iii) Water-soaked small and round lesions are seen on infected paddy shoots.
(iv) Diseased paddy is sterile, the paddy is stunted and yield is reduced by 60%.
(v) Diseased rice grains do not bear fruit.
Treatment of rice leaf blight disease
1. Healthy, vigorous, disease-free and disease-resistant varieties should be used. High yielding varieties resistant to leaf blight are Xa4, Xa5, Xa13, Xa21, Xa33, Xa38 etc.
2. The seeds should be treated with fungicide before sowing. The seeds should be treated with bleaching powder (100 mg/ml) and zinc sulphate (2%).
3. Spraying streptocycline on diseased leaves is beneficial.
4. Weeds and garbage on the land should be destroyed or burnt. Paddy straw and other growing plants should be removed.
5. The land should be well dried before sowing.
6. Phenyl sulfuric acetate and m. 10-20 liters of Chloramphenicol should be applied.
7. Water drainage should be arranged.
8. Seed beds should be made on high ground. Plant to plant distance and line to line distance should be scientific.
9. Disinfect the soil by spreading copper oxychloride.
10. Chlorine or bleaching powder should be applied with irrigation water.
11. Nitrogen fertilizers should be applied in the right amount at the right time. Do not overdose.
12. Diseased rice plants should be uprooted and burnt.
13. Seed borne infection is prevented by soaking in 0.1% Sirisan solution for 8 hours before sowing.
14. Quarantine procedures should be adopted.
What will be the disaster if there is an epidemic of rice leaf blight?
1. Food shortage: If rice leaf blight disease occurs in epidemic form, rice yield will decrease. Paddy cultivation will decrease a lot. The food needs of the growing population will not be met. There will be extreme food shortage in the country.
2. Economic collapse: If rice disease becomes an epidemic in the country, the production of other crops will be greatly affected. There will be a slowdown in business. Family and national economy will be greatly affected. As a result, the economy will collapse.
3. Agricultural disaster: If rice leaf blight becomes epidemic, rice and other crops will be greatly affected. Paddy cultivation will be stopped for 1-3 years in certain areas. As a result there will be agricultural disaster.
4. Dissatisfaction of farming families: If rice diseases spread in epidemic form, the yield of rice will decrease. Rice production will decrease. Paddy cultivation will be stopped. The agricultural families will be in financial crisis. As a result, there will be widespread dissatisfaction among the populous agricultural families.
5. Forestry Disasters: Rice diseases can spread along with other plant diseases. Different plants can be affected. Plantation operations will be hampered due to disease outbreaks. Tree planting programs may be discontinued. As a result, there will be a forest disaster.
6. Import of food from abroad: Rice production will decrease due to epidemic. Paddy cultivation will stop. There will be food shortage in the country. Food needs to be imported from abroad to meet the food demand.
7. Stop export of goods: Panic will be created in the country and neighboring countries due to the epidemic. Pathogens can spread with different products. Diseases are likely to spread from one area to another and from one country to another. Therefore, the export of goods abroad will be stopped.
8. Stopping industrial production: The raw material of industry is agricultural products. Due to the rice epidemic, the supply of raw materials to the industry will be severely disrupted. As a result, industrial production may stop due to lack of raw materials.
9. Increase in unemployment: Rice production will stop due to epidemics. Other agricultural production will decrease. There will be a slowdown in domestic and foreign trade. Industrial production will decrease. As a result, unemployment will increase.
10. Weed Outbreaks: Crop production can be stopped due to epidemics. Weeds will continue to grow naturally. Weeds will produce lots of seeds. This will greatly increase the prevalence of weeds.
