Asexual stage: pyricularia oryzae ( p. grisae )

Sexual stage:  Magnaporthe grisea

First time reported in Nepal in 1966 A.D.

The typical symptoms appear on leaves, leaf sheath, rachis, nodes and even the glumes are also attacked.

Leaf blast

• Small water soaked bluish green specks,soon enlarge diamond shaped spots with grey centre and dark brown margin.

Node blast:

• In infected nodes, irregular black areas that encircle the nodes can be noticed.
• The affected nodes may break up and all the plant parts above the infected nodes may die (Node blast).

Collar blast:

• The collar of a rice plant refers to the junction of the leaf blade and the sheath.
• Necrosis at the union of the two tissues.
• Collar infections can kill the entire leaf and may extend a few millimeters into and around the sheath.

Neck or Panicle blast:

• The neck of the rice plant refers to that portion of the stem that rises above the leaves and supports the seed head or panicle.
• At the flower emergence, the fungus attacks the peduncle which is engirdled, and the lesion turns to brownish-black.
• Referred to as rotten neck/neck rot/neck blast/panicle blast.
• In early neck infection, grain filling does not occur and the panicle remains erect like a dead heart caused by a stem borer. In the late infection, partial grain filling occurs.
• Lesions can be found on the panicle branches, spikes, and spikelets.
• The lesions are often gray brown discolorations of the branches of the panicle, and, over time, the branches may break at the lesion.

Rice seed

• Brown spots, blotches, and occasionally the classic diamond-shaped lesion often seen on leaves.