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Rice tungro disease is caused by two viruses (RTBV and RTSV) transmitted by the green leafhopper (Nephotettix virescens) and related species. It is the most damaging viral disease of rice in South and Southeast Asia. There is no cure once infection is established; management is entirely preventive.

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When rice is most vulnerable

Early - from seedling through active tillering. Late infection causes far less yield loss than infection within the first 30 days.

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How tungro shows in satellite data

  • Yellow-orange patches with reduced NDVI appearing in the first 30 to 60 days.
  • Patches are typically irregular and spreading as leafhoppers move outward from a focus.
  • Field edges bordering leafhopper reservoirs (grasses, older rice fields nearby) often affected first.
  • Signature overlaps with iron toxicity and N deficiency; confirm with leafhopper trapping and symptom check.
Tungro looks like a nutrient problem from above. If a fertilizer top-dressing does not green up the affected patches within a week, suspect tungro or iron toxicity.

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Field symptoms

  • Yellow to orange-yellow discoloration, starting on the tip of young leaves and progressing downward
  • Stunted plants with reduced tillering
  • Delayed flowering, sterile or partially filled panicles
  • Symptoms appear 1 to 2 weeks after leafhopper feeding

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Reduce the damage by

  • Grow resistant varieties where tungro is chronic (IR64 and several IRRI lines carry useful resistance).
  • Synchronized planting across a whole area breaks the leafhopper build-up cycle - avoid staggered planting.
  • Destroy volunteer rice and grass hosts between seasons.
  • Manage the vector - inspect early for green leafhopper; apply a selective insecticide only if scouting justifies it. Broad-spectrum insecticides can trigger BPH outbreaks and are counter-productive.
  • Do not replant heavily infected fields with a susceptible variety - the source of inoculum remains high.

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Set an alert for early warning

Turn the diagnosis into a trigger. Configure early-establishment alerts so any patchy yellowing within the first 30 days is flagged for scouting.
Recommended settings for tungro on rice:
  • NDVI threshold alert at 21 to 45 days after transplanting.
  • New Imagery alert during the vector active period so patchy yellowing is caught within days.