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Finger millet blast (Pyricularia grisea) Photo: No machine-readable author provided. Fk assumed (based on copyright claims). · CC BY 2.5 · source ↗

Finger millet blast (Pyricularia grisea)

Blast caused by the fungus Pyricularia grisea (= Magnaporthe grisea) is the single most damaging disease of finger millet (Finger Millet Ragi Cultivation) in India. The pathogen is the same species complex that causes blast in rice and several other grasses, but the finger-millet pathotype is host-adapted. It can destroy 20-80% of yield in a susceptible field during a wet, cloudy growing season.

Identification and symptoms

Three syndromes are distinguished by extension pathologists:

  • Leaf blast — spindle-shaped lesions on leaves with a grey-white centre and brown margin. Lesions enlarge and coalesce, drying out the leaf.
  • Neck blast — black-brown necrosis at the peduncle node where the panicle emerges. The neck often breaks, resulting in chaffy heads and severe yield loss.
  • Finger blast — necrotic lesions on individual fingers of the ear that turn the affected portion grey and prevent grain filling. Single fingers or whole panicles may be lost.

Hosts and lifecycle

The fungus survives between seasons on crop residue, on seed and on collateral grass hosts. Conidia are dispersed by wind and water-splash. Disease pressure is greatest under prolonged leaf wetness, cool nights, 24-28 degC day temperatures and high relative humidity — typical of the late August-September period in southern peninsular India when ragi is in the head-emergence stage.

Damage and economic impact

Neck and finger blast cause direct grain loss; leaf blast contributes by reducing photosynthetic area. AICRP-SM trials and IIMR surveys record 10-30% yield loss in most years with epidemic years reaching 60% or more, especially on susceptible local landraces.

Management

Integrated management as recommended by ICAR-IIMR and AICRP-SM:

  • Resistant varieties — GPU-28, GPU-66, GPU-67, VR-708, ML-365 and many recent AICRP releases carry good field resistance.
  • Seed treatment — Trichoderma viride at 4 g/kg seed, or carbendazim at 2 g/kg seed.
  • Cultural — clean ploughing to bury residue; balanced N application (avoid excess urea which softens tissue); timely sowing.
  • Foliar sprays — tricyclazole 0.06% (75 WP at 0.6 g/L) or carbendazim 0.1% at neck-emergence and again 10-15 days later. Hexaconazole and propiconazole are alternatives.
  • Biological — Pseudomonas fluorescens talc formulations at 10 g/L as a foliar spray have shown promise in IIMR trials.

See also: Finger Millet Ragi Cultivation, Tikka Leaf Spot Groundnut, Pearl Millet Bajra Sajja Cultivation.

Sources

  1. Finger Millet Blast — fact sheet. ICAR-Indian Institute of Millets Research, Hyderabad.
  2. AICRP on Small Millets — pathology recommendations. UAS Bengaluru.
  3. Management of finger-millet blast. Indian Phytopathological Society.