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Diseases

Diseases
25
Jun

Introduction to Bacterial Leaf Blight: Xanthomonas campestris pv. oryzae

Introduction:
 
1.Bacterial blight caused by Xanthomonas campestris pv. oryzae, became prominent after the introduction of nitrogen responsive, high yielding rice variety T(N)1, in mid-sixties.

File Courtesy: 
ADVANCES IN INTEGRATED RICE DISEASE MANAGEMENT ( Dr. krishnaveni)
Photo Courtesy: 
Rice Blast Disease and its Management ( Dr . Krishnaveni)
25
Jun

Flowering and after  management for rice blast

Chemical control of rice blast disease at flowering and after flowering:

1. A susceptible variety is grown in the field.

 

2. The crop has excessive growth and a dense canopy.

3. Leaf symptoms have been found in the field.

4. Disease is present in southern parts of the field.

5. Cool, rainy, or cloudy weather with high humidity and heavy dews is predicted during heading.

File Courtesy: 
http://www.ikisan.com/links/ap_riceDetailedStudyofDiseases.shtml
25
Jun

Pre-Tillering to Mid-Tillering management for rice blast

 

Chemicals to control rice blast disease at pre tillering to mid tillering stages are

1.At 5 % leaf area damage or 1 to 2 % neck infection spray Edifenphos, Carbendazim@0.1 % or Triclyclazole @ 1 gm /lit of water.  

 

File Courtesy: 
http://www.ikisan.com/links/ap_riceDetailedStudyofDiseases.shtml
25
Jun

Chemical control for Rice Blast

1. In endemic areas, adopt seed treatment with 

File Courtesy: 
http://www.ikisan.com/links/ap_riceDetailedStudyofDiseases.shtml
25
Jun

Cultural Practices to control rice blast

1.Healthy seeds collected from disease free fields should be used.
 

2. Destruction of weeds, collateral hosts and crop residues can greatly reduce the primary inoculum and terminal disease severity.

3. Seedlings should be raised in the water covered seed beds. Seedlings raised in upland nurseries are more susceptible to blast even after they are transplanted. Rice varieties with lower silicon content in the epidermal cells are after affects. 

File Courtesy: 
Rice Blast Disease and its Management ( Dr. Krishnaveni)
25
Jun

Host plant resistance of Rice Blast

1. Developing rice varieties with highly effective and durable resistance to blast is the most promising choice.
 

2. Breeding for resistance to blast has, however, often been frustrated by the rapid adaptation of the pathogen population to resistant cultivars.

3.Many varieties have been reported to be resistant to this disease.

File Courtesy: 
Rice Blast Disease and its Management ( Dr. Krishnaveni)
25
Jun

Management Principles of Rice Blast

1. Among several methods available for the management of the disease, chemical control has been found very successful and widely practiced in many countries.

2.However, due to concern over the excessive use of chemical pesticides, emphasis is being given towards alternative approaches for the management of the disease.

3.  Development of an integrated approach by combining the effective cultural, chemical and host plant resistance components would be ideal for the management of this dreaded disease.

 

File Courtesy: 
Rice Blast Disease and its Management ( Dr. Krishnaveni)
25
Jun

Pre-disposing Factors of Rice Blast

 

1.The presence of a thin film of water on the leaf surface favors the infection.

2.Low night temperature (below 240C) coupled with high relative humidity favors the dew formation on the leaf surface and thus, helps in rapid spread of the disease.

3. Blast is more severe in upland than in lowland ecosystem. 

 

File Courtesy: 
Rice Blast Disease and its Management ( Dr. Krishnaveni)
25
Jun

When damage is important of Rice Blast

Important stage for the damage by Rice Blast: 

1. Rice blast infects the rice plant at any growth stage. 

2. Rice seedlings or plants at the tillering stage are often completely killed. Likewise, heavy infections on the panicles usually cause a loss in rice yields.

 

File Courtesy: 
http://www.knowledgebank.irri.org/ricedoctor/ index.php?option=com_content&view=article &id=562&Itemid=2767
25
Jun

Mechanism of damage of Rice Blast

1. Disease cycle begins when conidia are deposited on rice leaves and germinate by producing a germ tube and an appressorium. 

2. Under favorable conditions, symptoms within 4-5 days of infection.

3. Conidia are produced on the lesions 6-7 days after infection. The rate of sporulation increases with increase in relative humidity (RH). 

File Courtesy: 
Rice Blast Disease and its Management ( Dr. Krishnaveni)
25
Jun

Host range of Rice blast

 In tropics, air borne conidia are present all through the year, because of the availability of collateral host grasses such as Setaria intermecia, Digitaria marginata, Panicum repens and Leersia hexandra. 

File Courtesy: 
http://www.ikisan.com/links/ap_rice DetailedStudyofDiseases.shtml
25
Jun

Causal organism (Pathogen) of Rice blast

Causal organism of the rice blast disease is Pyricularia grisea (P.oryzae)

File Courtesy: 
Rice Blast Disease and its Management ( Dr . Krishnaveni)
25
Jun

Parts affected by blast

Parts affected by blast: 

The plant parts which effected by the rice blast disease:

  • Leaf 
  • Collar 
  • Node 
  • Neck

 

File Courtesy: 
Rice Blast Disease and its Management ( Dr. Krishnaveni)
25
Jun

Symptoms of Neck blast

Symptoms of Neck blast :

1.The neck blast also called as neck rot or rotten neck.

2.The neck rot or rotten neck blast phase is caused by infection of the neck node by the fungus Pyricularia oryzae. 

3.Rotten neck symptoms appear at the base of the panicle starting at the node.

4.The infected tissue turns dark brown to black and shrivel causing the stem to break.

File Courtesy: 
Rice Blast Disease and its Management ( Dr. Krishnaveni)
Photo Courtesy: 
Rice Blast Disease and its Management ( Dr . Krishnaveni)
25
Jun

Symptoms of Node blast

Symptoms for the identification of rice blast disease:

  • When the nodes are infected, irregular black areas encircle the nodes and the nodes rot.
  • The affected nodes may break up and all the plant parts above the infected nodes may die. 

 

File Courtesy: 
Rice Blast Disease and its Management ( Dr. Krishnaveni)
Photo Courtesy: 
DRR Manual (Rice Blast Disease and its Management)
25
Jun

Symptoms of Panicle blast

 

Symptoms of Panicle blast

 

 

1. At the time of flowering, areas near the panicle base are often attacked causing ‘rotten neck’ or ‘neck rot’ symptoms. 

2. Blackening at the principal nodes below the flowering axis is known as neck infection. 

3. The neck becomes shrivelled and covered with grey mycelium. 

File Courtesy: 
Rice Blast Disease and its Management ( D . Krishnaveni)
25
Jun

Collar blast

Symptoms of Collar blast 

 

 

1. The collar rot phase occurs due to infection at the junction of the leaf blade and sheath, resulting in development of characteristics brown to dark brown lesion.

2. Severe collar rot infection on the flag or second to last leaf often kills the entire leaf. 

File Courtesy: 
Rice Blast Disease and its Management ( D . Krishnaveni)
25
Jun

Leaf blast

Leaf blast: 

 

1.The symptoms start with the appearance of small whitish, greyish or bluish spots of 1-3 mm diameter on the leaf blades.

File Courtesy: 
Rice Blast Disease and its Management ( D . Krishnaveni)
Photo Courtesy: 
Mr.Chaitanya - DRR
25
Jun

Symptoms of Rice Blast

 Symptoms  of  Rice Blast

  • The fungus affects the leaves, nodes and panicles and produces characteristic symptoms.

 

File Courtesy: 
Rice Blast Disease and its Management ( D . Krishnaveni)
Photo Courtesy: 
CRRI
25
Jun

Economic importance of Rice Blast

 

Economic importance of  Rice Blast

Economic losses due to rice blast disease:

  • The yield loss due to this disease may be as high as 75% or more in disease conducive conditions.

 

File Courtesy: 
Rice Blast Disease and its Management ( Dr . Krishnaveni)
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