Rice Blast Management

                                                                                           S. Parthasarathy,

                                 Ph.D Scholar, Dept. of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore

Blast : Causal Organism : Pyricularia Oryzae (Syn:P.grisea)

Sexual Stage : Magnaporthe grisea)

Symptoms:                                                

            Attacks the crop at all stages from seedlings  in Nursery to heading in main field.

i)                Leaf Blast :  On the leaves, the lesions start as small water soaked bluish green flecks, soon enlarge and spindle shaped spots with grey centre and dark brown margin.

ii)              Node Blast :  Infected Nodes, irregular black areas encircle the nodes.  It may break up all the plant parts above the infected nodes may die.

iii)            Neck Blast (Rotten reck / Neck rot / panicle blast) : At the flower emergence, the fungus attacks the peduncle which is engirdled, and the lesion turns to brownish – black.  Grain filling does not occur.

Pathogen:

            Mycelium of the fungus, is hyaline to olivaceous, septate highly branched.  Conidia are produced in clusters.  The ascospores are hyaline, furiform, 4 celled, and slightly curved.

Mode of Spread and Survival:

            The disease spreads primarily through airborne conidia.  Mycelium and conidia in the infected straw seeds are important sources of in oculum.  The fungus also survives on collateral hosts viz.  Panicerm, repens, Brachiaria Mutica, Enhinochloa Crusgalli).

Management :

            Grow resistant varieties like Ponmani, ADT 40, IR 20, ADT 37, Vikas, Jaya.  Avoid cultivation of highly susceptible varieties viz., IR50 & TKM6. Remove and destroy the weed hosts in the field.  Treat the seeds with captan or Thiram or Carbendazim at 2 g/kg.  Seed treatment with biocontrol agent Trichoderma viride @ 4g/kg (or) Pseudomonas fluorescens @ 10g/kg of seed.  Spray the Nursery with Carbendazim 25g, mainfield with Edizenphos 250 ml.