Brown leaf spot:

Causal organism: Helminthosporium oryzae (Cochliobolus miyabeanus)

• Soils deficit in silica, potassium, manganese or magnesium or hydrogen sulphide presence favours the disease.
• Brown spot disease also attacks the plant when nitrogen deficiency is induced at late growth stages.
• Plants are less susceptible when soils have low phosphorus levels.

Symptoms:

• Disease appears on the leaves and the glumes.
• The typical spots on leaves are oval, uniform and evenly distributes over the leaf surface.
• Young or undeveloped spots are small, circular and appear as dark-brown or purplish-brown dots while when fully developed they are brown with a grey or whitish centre.
• On glumes, black or dark-brown spots appear which cover entire glumes in severe cases.
• Under favourable climatic conditions, dark-brown conidiospores and conidia develop on these spots, giving them a velvet-like appearance.                              

    

Management:

Grow resistant varieties such as Dakar Nagra, 273-22, 5-34-33, Patnai 23, Kalma 219, Nagra 41-14, Ch 13, Ch 45, T-141, Co 20, T-498-2A, BAM-10, IR 42, T-988 m, T-2112 and T-960