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Stem borer larvae tunnel inside the rice stem, cutting off water and nutrient supply to the tiller. At vegetative stage, this kills the central growing point and produces a deadheart (dead central tiller pulled out easily). At reproductive stage, it cuts the panicle base and produces a whitehead (pale, empty panicle standing above the crop). The main species are yellow stem borer (Scirpophaga incertulas), striped stem borer (Chilo suppressalis), pink stem borer (Sesamia inferens), and dark-headed stem borer (Chilo polychrysus). Management is similar across species.

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When rice is most vulnerable

Entire vegetative to reproductive period. Vegetative-stage damage causes deadhearts; reproductive-stage damage causes whiteheads. Whiteheads cause greater yield loss because the tiller is no longer replaceable.

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How stem borers show in satellite data

  • Whiteheads at heading appear as small pale flecks and, in heavy infestations, as reduced field-scale NDVI at the reproductive stage.
  • Deadhearts at tillering do not usually cross the detection threshold from satellite - the plant compensates with new tillers.
  • Sudden pale patches after heading, with no weather cause, are a stem-borer signal.
Whiteheads look the same from above whether caused by stem borer, neck blast, drought at flowering, or sheath rot. Ground confirmation is essential.

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Field symptoms

  • Deadheart (vegetative stage): central tiller dries out and can be pulled out easily; the rest of the plant looks normal
  • Whitehead (reproductive stage): whole panicle is pale, dry, empty, and stands above the healthy crop
  • Larval tunnels visible when the stem is split open
  • Frass (insect droppings) in the tunnels
  • Egg masses on leaves - flat cream/brown patches near the leaf tip

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Reduce the damage by

  • Grow moderately resistant varieties where available.
  • Destroy egg masses during weeding and hand-remove infested tillers.
  • Synchronized planting and destruction of stubble between seasons reduces the carryover population.
  • Preserve natural enemies - egg parasitoids (Trichogramma) provide substantial free control. Avoid broad-spectrum insecticides.
  • Release Trichogramma cards where they are available and locally validated.
  • Selective insecticide (chlorantraniliprole or cartap) only if scouting shows the economic threshold is crossed. Apply based on egg-mass counts, not calendar.
  • Do not spray at heading to protect pollinators and beneficials.

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Set an alert for early warning

Turn the diagnosis into a trigger. Focus alerts on the reproductive stage where whiteheads become detectable.
Recommended settings for stem borers on rice:
  • NDVI drop alert during heading - trigger on a drop of 0.08 or more.
  • New Imagery alert during the two weeks around heading so early whitehead patches are caught quickly.