Brown Spot Disease of Rice is almost worldwide in distribution. But it is occurred severely in South-East Asia, Philippines, Japan etc. This disease spreads by seed and due to non-selective export to other countries. This disease is also known as Helminthosporiosis.
In India, Sundarraman reported first in 1922 about this disease. now this disease is too common in all rice growing regions. In the Indian states of West Bengal, Assam, Tamil Nadu, Uttar Pradesh ( Eastern Region), Andra Pradesh and few regions of Kerala, most of the stage of seedling infected.
In West Bengal, this disease is much common and it occurs both on Kharif and Rabi crops, mainly in tracts where rice is grown by irrigation system.
Importance: The disease causes great economical losse on Paddy Cultivation.
Collateral Host:
The pathogen of this disease can survive on some grasses. Out of cultivation season, these plants like Leersia hexandra, Echinochloa colonum etc acts as collateral host.
Causal Organism: The causal Organism i.e., Cochliobolus miyabeanus which is formerly known as Helminthosporium oryzae .
* Previous year's infected plant debris also acts as source of primary inoculum.
Rice Production of India:
Rice is one the almost three most important cereal food crop in the world. It is the staple food for over 2.7 billion people.
References:
1. A Text Book of Botany, Vol-I by Hait, Bhattacharya and Ghosh. Page 455-458
2. www.knowledgebank.irri.org
3. TNAU and others.
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| Brown Spot on Leaf, Source: knowledgebank.irri.org |
In India, Sundarraman reported first in 1922 about this disease. now this disease is too common in all rice growing regions. In the Indian states of West Bengal, Assam, Tamil Nadu, Uttar Pradesh ( Eastern Region), Andra Pradesh and few regions of Kerala, most of the stage of seedling infected.
In West Bengal, this disease is much common and it occurs both on Kharif and Rabi crops, mainly in tracts where rice is grown by irrigation system.
Highlights:
- The outbreak of this disease in Bengal was in 1942, caused up to 90% loss in yields and caused Bengal Famine in 1943 in India.
- It was a possible agroterrorism weapons.
Importance: The disease causes great economical losse on Paddy Cultivation.
Symptoms of Disease:
1. On Coleoptile:
Symptoms on the Coleoptile appear like spots, are brown, small, pinhead to oval in shape. The coleoptile becomes blighted and causes death of seedlings.
Symptoms on the Coleoptile appear like spots, are brown, small, pinhead to oval in shape. The coleoptile becomes blighted and causes death of seedlings.
2. On Leaf blade:
On the leaf blade appear as discrete, dark brown, elliptical to eye shaped spots. A fully developed spot is like greyish brown centre surrounded by reddish brown margin.
On the leaf blade appear as discrete, dark brown, elliptical to eye shaped spots. A fully developed spot is like greyish brown centre surrounded by reddish brown margin.
3. On Leaf sheath:
Symptoms on Leaf sheath is very similar to the leaf blade.
Symptoms on Leaf sheath is very similar to the leaf blade.
4. On Inflorescence:
In the early stage if inflorescence infected, it does not develope any grain.
In the early stage if inflorescence infected, it does not develope any grain.
Collateral Host:
The pathogen of this disease can survive on some grasses. Out of cultivation season, these plants like Leersia hexandra, Echinochloa colonum etc acts as collateral host.
Causal Organism: The causal Organism i.e., Cochliobolus miyabeanus which is formerly known as Helminthosporium oryzae .
Disease Cycle:
During the germination of infected seeds,the coleoptile gets infected and gradually it affects the seedling, showing blight and others symptoms.
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| Disease Cycle in word diagram, Image: biologydiscussion.com |
* Previous year's infected plant debris also acts as source of primary inoculum.
Methods of Disease Control:
The following methods of can be controlled or reduced the disease:
The following methods of can be controlled or reduced the disease:
1. Cultural methods:
A. Eradication of collateral host: Collateral host should be eradicated.
B. Sanitation: Cleaning and burning of the previous year's plant debris are very fruitful to reduce the disease.
C. Irrigation system: During irrigation, trhe water should not pass form the infested field to the field without disease.
D. Leaching of metals: Leaching of metals should be checked.
E. Application of metals: Addition application of metals like K in the field during growth period, reduce the severity of the disease.
F. Spacing: During transplantation, proper spacing can reduce the disease incidence.
G. Nitrogen fertilizer: Application of Optimum nutrition fertilizer (Urea), transplanting at the optimum dates proved to be helpful.
2. Physical control:
A. Sunlight: Soaking the seeds for 24 hours in water then drying it in bright sunlight (52°-54°C) reduces the source of primary inoculum by killing the mycelium.
B. Hot water treatment: Hot water treatment at 55°C for 10 mins is very fruitful.
C. Cold water treatment: According to CRRI, some resistance can develop inside the seedling if the seeds are allowed to germinate in cold water.
3. Chemical control:
A. Seed treatment: Dry dressing of the infected seeds with Ceresan or Agrosan GN at 2-2.5% reduce the disease. Wet treatment of seeds have been found to very effective in controling the disease.
B. Foliage treatment: Spraying or dusting of fungicide, two or three time atva regular intervals give effective control of disease.
4. Disease Tolerant Varieties: Use of disease tolerant varieties of rice cultivation is better than others which are less costly.
A number of disease tolerant varieties are developed in Central Rice Research Institute( CRRI) in Cuttack, Orissa, India.
A. Eradication of collateral host: Collateral host should be eradicated.
B. Sanitation: Cleaning and burning of the previous year's plant debris are very fruitful to reduce the disease.
C. Irrigation system: During irrigation, trhe water should not pass form the infested field to the field without disease.
D. Leaching of metals: Leaching of metals should be checked.
E. Application of metals: Addition application of metals like K in the field during growth period, reduce the severity of the disease.
F. Spacing: During transplantation, proper spacing can reduce the disease incidence.
G. Nitrogen fertilizer: Application of Optimum nutrition fertilizer (Urea), transplanting at the optimum dates proved to be helpful.
2. Physical control:
A. Sunlight: Soaking the seeds for 24 hours in water then drying it in bright sunlight (52°-54°C) reduces the source of primary inoculum by killing the mycelium.
B. Hot water treatment: Hot water treatment at 55°C for 10 mins is very fruitful.
C. Cold water treatment: According to CRRI, some resistance can develop inside the seedling if the seeds are allowed to germinate in cold water.
3. Chemical control:
A. Seed treatment: Dry dressing of the infected seeds with Ceresan or Agrosan GN at 2-2.5% reduce the disease. Wet treatment of seeds have been found to very effective in controling the disease.
B. Foliage treatment: Spraying or dusting of fungicide, two or three time atva regular intervals give effective control of disease.
4. Disease Tolerant Varieties: Use of disease tolerant varieties of rice cultivation is better than others which are less costly.
A number of disease tolerant varieties are developed in Central Rice Research Institute( CRRI) in Cuttack, Orissa, India.
Some varieties: IR-8, IR-24, CH13, CH20, CH45, T141, T2114, IET13238, CR84-30, JB83 etc.
Rice is one the almost three most important cereal food crop in the world. It is the staple food for over 2.7 billion people.
References:
1. A Text Book of Botany, Vol-I by Hait, Bhattacharya and Ghosh. Page 455-458
2. www.knowledgebank.irri.org
3. TNAU and others.
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