> ## Documentation Index
> Fetch the complete documentation index at: https://badixth-dc85e378.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Cold Snap and Haze Stress in Rubber

> How cool nights and prolonged transboundary haze suppress rubber growth and latex flow, and how to interpret the satellite signal during haze episodes.

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.

## 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

## Effect

| Event                       | Effect                                                                                |
| --------------------------- | ------------------------------------------------------------------------------------- |
| Cold nights                 | Latex flow reduction (10 to 20%), delayed refoliation                                 |
| Moderate haze (API 100-200) | Solar radiation reduced 10 to 20%, latex flow -5 to -10%                              |
| Severe haze (API > 200)     | Solar radiation reduced 30 to 50%, latex flow -15 to -30%, delayed wintering recovery |
| Prolonged haze (> 3 weeks)  | Canopy thinning, elevated CLF risk (weakened trees)                                   |

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)

## Satellite signals

| Index                                     | What to watch                  | Notes                             |
| ----------------------------------------- | ------------------------------ | --------------------------------- |
| NDVI                                      | Slight dip during haze         | Small, region-wide                |
| PAR (photosynthetically active radiation) | Direct drop                    | Best indicator; use ERA5 or MODIS |
| Aerosol optical depth (AOD)               | Direct haze measure            | Confirms cause                    |
| LST                                       | Suppressed daytime temperature | Confirms overcast                 |

## Action

<Steps>
  <Step title="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).
  </Step>

  <Step title="Reduce tapping intensity">
    During prolonged haze, switch from d/2 to d/3 to conserve tree reserves and prevent TPD.
  </Step>

  <Step title="Postpone stimulation">
    Do not apply ethephon during haze; trees cannot recover the stored photosynthates.
  </Step>

  <Step title="Monitor for CLF post-haze">
    Weakened trees are more susceptible to [Corynespora leaf fall](/guides/Crop/Rubber/biotic/diseases/corynespora) in the refoliation window following haze.
  </Step>
</Steps>

## Recommended alert settings

| Trigger                    | Condition                           | Severity |
| -------------------------- | ----------------------------------- | -------- |
| Haze                       | API > 150 for 7+ days               | Medium   |
| Severe haze                | API > 200 for 7+ days               | High     |
| Solar radiation            | PAR \< 70% of baseline for 14+ days | Medium   |
| Cold night (highland only) | \< 18 C for 5+ consecutive nights   | Low      |

## Related

* [Corynespora leaf fall](/guides/Crop/Rubber/biotic/diseases/corynespora)
* [Tapping Panel Dryness](/guides/Crop/Rubber/biotic/tpd)
* [Rubber Diagnosis](/guides/Crop/Rubber/rubber-diagnosis)