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Malaysian rubber rarely faces temperature stress but is affected by two atypical events: cool highland nights (Cameron Highlands, some Sarawak upland blocks) and prolonged transboundary haze from Sumatra/Kalimantan peat fires (typically Aug to Oct in El Nino years). Haze cuts solar radiation, suppresses photosynthesis, and reduces latex flow across whole regions.

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Cause

  • Cool nights (< 18 C sustained) at highland sites (> 400 m elevation)
  • Transboundary haze with API/PSI > 150 for 2+ weeks
  • Reduced solar radiation during prolonged overcast periods

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Effect

Field signs:
  • Latex flow drop across the whole estate (not localized)
  • Grey ash deposit on canopy after major haze episodes
  • Delayed refoliation in the following season
  • Reduced DRC (dry rubber content)

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Satellite signals

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Action

1

Confirm the cause

Check API/PSI readings and satellite AOD. Haze is region-wide, not block-specific, so if only one block is affected, look elsewhere (drought, disease).
2

Reduce tapping intensity

During prolonged haze, switch from d/2 to d/3 to conserve tree reserves and prevent TPD.
3

Postpone stimulation

Do not apply ethephon during haze; trees cannot recover the stored photosynthates.
4

Monitor for CLF post-haze

Weakened trees are more susceptible to Corynespora leaf fall in the refoliation window following haze.