PGRFA

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The Disease:  BROWN SPOT
Pathogen:
Bipolaris oryzae (Breda de Haan) Shoemaker
Other acceptable names: Dreschlera oryzae and Helminthosporium oryzae
Teleomorph: Cochliobolus miyabeanus (Ito and Kuribayashi) Dreschler ex Dastur

Etymology: from bipolaris, bipolar - referring to the bipolar germination of the spores
Disease:
Sir John Woodhead reported in 1945 that brown spot was the principal cause of the 1942 Bengal famine (cited in Ou 1985). Vidhyasekaran and Ramadoss (1973) reported that severe infections can reduce yield by 20 - 40%.

Symptoms: Conspicuous brown spots appear on the leaves. Spots measure 2-1 x 0.5 cm, are oval and evenly distributed. They are brown with gray or whitish centers on maturity. In severe infections, spots fuse and leaves wither. Spots also develop on glumes. When conditions favor fungal development, a velvety growth can be seen over the seeds, and the fungus may enter the glumes and leave blackish spots on the endosperm.

Brown spot symptoms may appear on the leaf coleoptile, leaf sheaths, and panicle branches. Blackish lesions may be seen on young roots.
Appearance:
bipolaris oryzae habit character brown spot observed in the field
Last Updated on Wednesday, 15 April 2009 05:56