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Sheath rot, caused primarily by Sarocladium oryzae, attacks the flag leaf sheath. Because the panicle emerges through the flag leaf sheath, sheath rot often traps or damages the panicle at heading. It thrives in dense high-N canopies with insect wounds, especially after brown planthopper or stem borer damage.

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When rice is most vulnerable

Booting through heading. Wounding by insects, high plant density, and continuous flooding all raise risk.

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How sheath rot shows in satellite data

  • Fields with heading failure show lower-than-expected NDVI at heading and no proper reproductive-stage green-up.
  • Poor separation from neck blast at the satellite level - use ground scouting and stubble examination.
A field that never green-fills at heading is a strong signal. Cause could be sheath rot, neck blast, drought at flowering, or panicle stem borer. Scout to separate them.

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Field symptoms

  • Oblong to irregular brown lesions on the flag leaf sheath, often with a pale center
  • Panicle fails to emerge fully, or emerges twisted and discolored
  • Powdery whitish growth inside the affected sheath in humid conditions
  • Unfilled or discolored grains; empty spikelets

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Reduce the damage by

  • Use clean, treated seed - sheath rot is seed-transmitted.
  • Avoid excessive N and dense planting.
  • Manage stem borer and brown planthopper - insect wounds are a major entry point.
  • Grow moderately resistant cultivars where available.
  • Balance nutrients - adequate K and Si reduce severity.
  • Fungicide may be justified at booting on chronic sheath-rot fields; use only with scouting evidence.

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Set an alert for early warning

Turn the diagnosis into a trigger. Sheath rot is best caught by comparing expected vs actual reproductive-stage NDVI, so schedule reviews at heading.
Recommended settings for sheath rot on rice:
  • NDVI threshold alert at heading - trigger when NDVI is below your ecosystem baseline for the reproductive stage.
  • New Imagery alert during heading so failed heading is caught within days.