Management of brown leaf spot of Rice

Brown leaf spot: Helminthosporium oryzae (Breda de Haan)(Deuteromycotina: Moniliales : Dematiaceae )

Local name: Kandu Chukke Roga

Brown spot is a fungal disease that can infect both seedlings and mature plants. This disease is more severe in areas of poor management..Major cause of 'Bengal Famine' in 1942, due to yield loss of 50-90%, resulting in death of 2 m people. Epidemics resulted in 14 to 41% losses in HYV's in India. Occurs mostly in deficient & poor soils (Poor man's disease). 

Period of occurrence: Seedling to maturity

Extent of yield loss: 50-90% in extreme cases

Collateral hosts: Digitaria sanguinalis, Leersia hexandra, Echinochloa colona, Pennisetum typhoides, Setaria italica, Cynodon dactylon.   

Favorable conditions for the pathogen

• Temperature of 25-30°C
• Relative humidity (>90%)
• Heavy and late north-east monsoon
• Cloudy days
• High doses of N

Mode of transmission/ dissemination: wind

Sources of inoculum: Seed, Collateral hosts, Rice straw or Stubble 

Damage symptoms

• The symptoms of the disease appear on the coleoptile, the leaves, leaf sheath and also the glumes.
• On the leaves the spots vary in size (1cm) and shape from minute dots to circular, eye shaped or oval spots is seen in the central portion.
• The seeds are some times shriveled and discolored.

  

Brown spot on leaf	Brown spot on earhead	Brown spot affected grains

Management

Preventive measures:

• Use of resistant varieties – Rasi, IR 36, Jagannath.
• Proper crop nutrition
• Avoid water stress
• Clean cultivation 

Cultural practices:

• Use disease free seeds for sowing.
• Do not use high nitrogenous fertilizer
• Use resistant variety Amruth

Chemical control:

• If the disease observed in the field than spray 1g of ediphenphos or 2g mancozeb or 2.25g Zineb in 1liter of water.