> ## 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.

# Powdery Mildew in Rubber

> Oidium heveae: attacks refoliation after wintering, prolonging the annual NDVI dip. Recognition, timing-critical fungicide sprays, and the northern-states risk profile.

**Powdery mildew** (*Oidium heveae*) attacks rubber during the refoliation window immediately after wintering. It kills young leaves as they emerge, prolonging the annual NDVI dip by 2 to 4 weeks and causing repeated flush loss. Most damaging in northern Peninsular states (Kedah, Perlis, Perak) where wintering coincides with cool, misty mornings.

## Cause

* **Cool nights (\< 22 C) with misty mornings** during refoliation (Feb-Apr)
* **Susceptible clones**: RRIM 600, some PB clones
* **Northern states** with more pronounced dry-cool wintering
* **Highland blocks** (> 300 m elevation)

## Effect

| Stage    | Symptom                                                                  |
| -------- | ------------------------------------------------------------------------ |
| Early    | White powdery growth on the underside of young leaves                    |
| Mid      | Leaves distorted, curled, blackened at margins                           |
| Late     | Whole flush dies back, tree must produce a second flush                  |
| Terminal | Repeated flush loss, delayed canopy recovery, delayed tapping resumption |

## Satellite signals

| Index        | What to watch                                   | Threshold                              |
| ------------ | ----------------------------------------------- | -------------------------------------- |
| NDVI         | Prolonged wintering trough                      | Recovery > 10 weeks (vs normal 6 to 8) |
| Anomaly view | Delayed refoliation vs prior year on same block | Direct comparison                      |

A slow post-wintering recovery in northern states is the diagnostic satellite signal for powdery mildew.

## Action

<Steps>
  <Step title="Confirm on new flush">
    White powder on the underside of expanding leaves confirms *Oidium heveae*.
  </Step>

  <Step title="Fungicide sprays (timing-critical)">
    Begin sprays **at start of refoliation** (first sign of new flush). Late sprays are ineffective.

    * **Sulphur dust** (30 kg/ha via mist blower), 3 to 5 rounds at 7 to 10 day intervals
    * Alternative: **hexaconazole** or **triadimefon**

    Northern states typically require the full 5-round program in outbreak years.
  </Step>

  <Step title="Adjust tapping">
    Do not resume tapping until the second flush is fully expanded. Premature tapping on partially-refoliated trees causes long-term yield loss.
  </Step>

  <Step title="Long-term: clone selection">
    On chronic northern blocks, favor mildew-tolerant clones at replanting.
  </Step>
</Steps>

## Recommended alert settings

| Trigger                 | Condition                                                        | Severity  |
| ----------------------- | ---------------------------------------------------------------- | --------- |
| Delayed refoliation     | NDVI recovery > 10 weeks after leaf fall onset                   | High      |
| Weather trigger         | Nighttime T \< 22 C + RH > 90% during Feb-Apr on northern blocks | Medium    |
| Northern-block reminder | Automatic Feb 1 spray-program reminder for northern estates      | Automatic |

## Related

* [Corynespora leaf fall](/guides/Crop/Rubber/biotic/diseases/corynespora)
* [Pestalotiopsis leaf fall](/guides/Crop/Rubber/biotic/diseases/pestalotiopsis)
* [Rubber ecosystems (wintering baselines)](/guides/Crop/Rubber/rubber-ecosystems)