Symptoms of Sheath Rot 

1. Symptoms usually develop as lesions on sheaths of lower leaves near the water line when plants are in the late tillering or early internode elongation stage of growth (approximately 10 – 15 days after flooding). 

Economic Importance of Sheath rot 

1. The economic importance of Sheath Rot : 

2. The Sheath rot disease appears late during the growing season of the rice crop.

3. It causes yield losses from 20% to 85% in Taiwan and 30% to 80% in Vietnam, the Philippines, and India.

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.

 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.

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.

Management Options of Stem Rot    

Stem rot disease management options include 

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

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.

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.

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.

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.

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.

Introduction to 

Stem Rot (Sclerotium oryzae)

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.