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Crop Protection

Crop Protection
27
Jun

Distribution and Occurrence of Sheath rot

 

The distribution and occurrence of sheath rot 

Sheath rot incited by Sarocladium oryzae, has become widespread in 

  • Andhra Pradesh, 
  • Kerala,
  • Orissa, 
  • Tamil Nadu, 
  • Bihar, 
  • West Bengal and
  • North Eastern States

 

File Courtesy: 
ADVANCES IN INTEGRATED RICE DISEASE MANAGEMENT ( Dr. krishnaveni)
27
Jun

History of Sheath rot

 

History of  Sheath rot

1. Sheath rot disease of rice was first reported to occur in India in 1978 (Agnihothrudu 1973).

2. The pathogen Sarocylindrium oryzae was revised later as Sarocladium oryzae ( Hawksworth, 1975).

3. The severe outbreaks caused considerable yield losses as in Punjab during 1978-79 

4. Nellore (1976). Seed borne internally and externally (Shajahan et al 1977).

 

File Courtesy: 
ADVANCES IN INTEGRATED RICE DISEASE MANAGEMENT ( Dr. krishnaveni)
27
Jun

Sheath Rot (Sarocladium oryzae)

The disease appears during heading to maturity stage of crop growth.

1. The pathogen generally attacks the upper most leaf sheath enclosing the young panicles.

2. Oblong or irregular spots with chocolate brown colour develop on the boot leaf sheath. Sheath rots disease of rice, caused by Sarocladium oryzae. 

3. It inflicts damage to the uppermost flagleaf sheath by infecting the sheath covering the young panicles at the booting stage.

File Courtesy: 
ADVANCES IN INTEGRATED RICE DISEASE MANAGEMENT ( Dr. krishnaveni)
Photo Courtesy: 
DRR Training Manual
27
Jun

Chemical control of Stem Rot

 

Chemicals used for the control of Stem rot disease are:

1. Fentin hydroxide sprayed at the mid-tillering stage, Thiophanate-Methyl sprayed at the time of disease initiation can reduce stem rot incidence.

2. The use of other fungicides such as Ferimzone and Validamycin A also show effectively against the fungus.

 

File Courtesy: 
http://www.knowledgebank.irri.org
27
Jun

Cultural control of Stem Rot

 

 The cultural control practices used for the control of Stem rot disease are: 

1. Burning straw and stubble or any crop residue after harvest or letting the straw decompose and draining the field can reduce sclerotia in the field.

2. A balanced use of fertilizer or split application with high potash and lime to increase soil pH reduces stem rot infection and increases yield.

 

File Courtesy: 
http://www.knowledgebank.irri.org
27
Jun

Host plant resistance of Stem Rot

Host plant resistance  of  Stem Rot    

The mechanism of host plant  for Stem rot disease 

1. The stem rot fungus may penetrate the plant directly or invade wounds. 

2. Practices that injure or stress rice plants (e.g., the use of phenoxy herbicides) have been shown to increase infection and disease development.

3. Use resistant varieties.

 

File Courtesy: 
http://www.ipm.ucdavis.edu/PMG/r682100211.html
27
Jun

Management Options of Stem Rot

 

Management Options of Stem Rot    

Stem rot disease management options include 

  • use of resistant varieties.
  • cultural control
  • chemical control

 

File Courtesy: 
http://www.ipm.ucdavis.edu/PMG/r682100211.html
27
Jun

Causal Organism and Pre-disposing factors of Stem Rot

Causal Organism of Stem Rot    

  • The causal organism for Stem rot disease is Sclerotium oryzae Cattaneo

Predisposing factors of Stem Rot    

The predisposing factors for Stem rot disease are:

1. Presence of infected bodies or sclerotia in the upper soil layer or on irrigation water.

2. Presence of wounds as entry points of the fungus.

3. Panicle moisture content.

4. Nitrogen fertilizer application.

File Courtesy: 
DRR training manual (Dr. krishnaveni)
27
Jun

Symptoms of Stem Rot

The symptoms of Stem rot 

1. The first symptom appears as small, black irregular lesions on the outer leaf sheath near the waterline. 

2. The fungus penetrates the inner leaf sheath resulting the basal portion of the stem to rot.

3. Numerous black, round shining bodies (sclerotia) are formed on the affected sheaths stems, and also in the hollow internodes at maturity.

File Courtesy: 
DRR training manual (Dr. krishnaveni)
Photo Courtesy: 
DRR Training Manual
27
Jun

Economic importance of Stem Rot

 

The economic importance of the stem rot disease is

1. Cause heavy losses in many countries. For example, in Japan, 51,000 to 122,000 hectares infected and estimated annual losses of 16,000-35,000 due to this disease. In Vietnam, the Philippines.

2. India, losses from 30% to 80% was recorded.

 

File Courtesy: 
http://www.knowledgebank.irri.org
27
Jun

Distribution and occurrence of Stem Rot

 

The distribution and occurrence of Stem rot disease are as follows 

1. The infected bodies or sclerotia are found in the upper soil layer. They survive in air-dry soil, buried moist rice soil, and in tap water. 

2. They can also survive on straw, which is buried in the soil. The sclerotia float on irrigation water and infect newly planted rice during land preparation.

File Courtesy: 
http://www.knowledgebank.irri.org
27
Jun

Stem Rot (sclerotium oryzae)

Introduction:

1. Stem rot is caused by Sclerotium oryzae, which survive through pin-head size sclerotia in rice straw and the soil. 

2. It is an important disease particularly in water-logged areas. 

3. The sclerotia produced by the fungus serve as primary inoculum source by floating on the water and infecting rice stems of the healthy plant at the waterline.

4. Sclerotia form abundantly in infected tissues as the rice plant nears maturity and continue to develop in crop debris.

 

File Courtesy: 
DRR training manual (Dr. krishnaveni)
27
Jun

Management options of Narrow Brown Spot

 

Control measures of Narrow Brown Spot disease: 

1. Cultural practices, such as the use of potassium and phosphorus fertilizers, and planting of early maturing cultivars early in the growing season, could manage this disease effectively.

2. Use of resistant varieties is the most effective approach to manage the disease.

3. Resistant varieties and lines are grown only in United States and India.

File Courtesy: 
http://www.knowledgebank.irri.org
27
Jun

Causal Organism and Pre-Disposing factors of Narrow Brown Spot Disease

Causal Organism:

The causal  organism for  Narrow Brown Spot disease is Cercospora janseana (Cercospora oryzae).

Pre-disposing factors:

The predisposing factors for Narrow Brown Spot are 

1. Rice crops grown on problem soil deficient in potassium

2. Temperature ranges from 25-28° C

3. Varieties grown are susceptible 

4. Disease incidence occur at growth stage.

 

File Courtesy: 
http://www.knowledgebank.irri.org
27
Jun

Symptoms of Narrow Brown Spot

 

The symptoms which are developed Narrow Brown Spot disease: 

1. The short narrow, elliptical to linear brown lesions appear on leaf blades sometimes they may also occur on leaf sheaths, pedicels, and glumes and rice hulls.

2. Lesions are about 2-10 mm long and 1 mm wide

3. Lesions are narrower, shorter, and darker brown on resistant varieties.

File Courtesy: 
http://www.knowledgebank.irri.org
Photo Courtesy: 
DRR Training Manual
27
Jun

Economic Importance of Narrow Brown Spot

 

The economic importance of the Narrow Brown Spot disease: 

1. Narrow Brown Spot disease on severe infection causes premature death of leaves and leaf sheaths, premature ripening of kernels and lodging of plants. 

2. It decreases the market value of the grains because of grain discoloration and chalkiness, and also reduces the milling recovery.

3. Yield loss of 40% was reported due to the incidence of disease in Suriname during the 1953 and 1954.
 

 

27
Jun

Distribution and Occurrence of Narrow Brown Spot

1. The Narrow Brown Spot disease has been reported in several countries in Asia, Africa, Australia, and Papua Guinea.

2. The disease is observed on rice crops grown on potassium deficient soils.

3. Temperature ranging from 25-28° C is favorable for the growth of the disease.

4. Susceptibility of the variety to the fungus and the growth stage of the rice crop are factors decide the development of the disease.

File Courtesy: 
http://www.knowledgebank.irri.org
27
Jun

Narrow Brown Spot ( Cercospora janseana)

Introduction

1. The Narrow Brown Spot disease varies in severity from year to year.

2. It becomes more severe when rice plant attains maturity, causing premature ripening and yield reduction. 

3. Leaf spots are long (1/10 to 1/2 inch), narrow (1/32 inch), and cinnamon-brown.

4. Premature leaf death occurs in severe cases. Early maturing varieties tend to escape the major impact of the disease.

File Courtesy: 
http://165.91.154.132/Texlab/Grains/Rice/ricenbls.html
Photo Courtesy: 
Rice Blast Disease and its Management ( Dr . Krishnaveni)
27
Jun

Management options of Leaf Scald

Management Options  of  leaf scald  

The Leaf scald disease can be controlled by different means. Those are:

1. The only cultural control practice, which is applicable for the disease is to avoid use of high amount of fertilizer.

2. There are some cultivars from India with resistance to the disease.

3. Chemicals such as Benomyl, Carbendazim, Quitozene, and Thiophanate-methyl can be used to treat the seeds to eliminate the disease. 

File Courtesy: 
http://www.knowledgebank.irri.org
27
Jun

Predisposing factors of Leaf Scald

Predisposing factors of Leaf Scald:  

The predisposing factors for Leaf scald disease are:

1. High nitrogen

2. Wet weather - close spacing of plants

3. Wounded leaves - sources of infection such as seeds and crop stubbles

 

File Courtesy: 
http://www.knowledgebank.irri.org
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