> ## 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.

# White Root Disease in Rubber

> Rigidoporus microporus: the most economically important root disease in Malaysian rubber. Recognition, expanding-focus scouting, and the cordon isolation and destroy protocol.

**White root disease** (*Rigidoporus microporus*, syn. *Rigidoporus lignosus*) is the number-one killer of Malaysian rubber. It spreads by root-to-root contact and by contact with infected stumps, forming expanding circular foci that can wipe out entire blocks if not stopped early. It is the top priority for the [Field Walk Protocol](/guides/Crop/Rubber/field-walk-protocol) root-collar inspection every quarter.

## Cause

* **Old rubber stumps** left in the ground at replanting (primary reservoir)
* **Adjacent forest or old rubber** at block boundaries
* **Root contact** with an infected neighbor
* **Waterlogging** weakens tree defenses and accelerates infection
* **Wound sites** on roots from ploughing or machinery

## Effect

| Stage    | Above-ground symptom                                             | Below-ground symptom                                       |
| -------- | ---------------------------------------------------------------- | ---------------------------------------------------------- |
| Early    | No visible above-ground symptom                                  | White rhizomorph fans on root surface                      |
| Mid      | Yellowing canopy on one side of the tree                         | Rhizomorphs spread up the root collar, root rot begins     |
| Late     | Wilting, defoliation, latex flow drop                            | Root system rotten, tree death within 6 to 12 months       |
| Terminal | Tree dead, fruiting bodies (orange bracket fungi) at collar base | Complete root destruction, adjacent trees already infected |

The disease spreads at 1 to 3 m per year from tree to tree. A focus that starts with one tree grows to 5 to 10 dead trees within 2 years if not stopped.

## Satellite signals

| Index         | What to watch                                         | Threshold          |
| ------------- | ----------------------------------------------------- | ------------------ |
| NDVI high-res | Localized declining cluster, expanding month-to-month | Direct observation |
| Anomaly view  | Same-block year-over-year, expanding low-NDVI patch   | Direct observation |

Cross-check any expanding cluster against the [rubber ecosystems](/guides/Crop/Rubber/rubber-ecosystems) baseline to distinguish white root from wintering.

## Action

<Steps>
  <Step title="Confirm at the collar">
    Scrape topsoil at the collar of the suspect tree. White fan-shaped rhizomorphs on the root surface confirm *Rigidoporus microporus*. If unsure, contact the Malaysian Rubber Board for confirmation.
  </Step>

  <Step title="Cordon isolation trench">
    Dig an isolation trench (60 cm deep, 30 cm wide) around the focus, at least 2 m outside the last infected tree. This severs root contact and stops horizontal spread.
  </Step>

  <Step title="Inspect every neighbor within 5 m">
    Scrape collar of every tree within 5 m in all directions from the infected focus. Root grafts spread the pathogen invisibly.
  </Step>

  <Step title="Fell, uproot, and burn infected trees">
    Fell all confirmed and probable trees. **Uproot the stumps** (do not leave them in the ground; they are the primary reservoir). Burn all root material on site.
  </Step>

  <Step title="Apply fungicide to remaining neighbors">
    Drench root collar of neighbors within 5 m with tridemorph (Calixin) or triadimefon (Bayleton) as per MRB recommendation. Repeat every 6 months for 2 years.
  </Step>

  <Step title="Sanitize tools">
    Wash all tools with fungicide or bleach between blocks. Never move root material or stump wood off-site.
  </Step>

  <Step title="Follow up">
    Re-inspect the treated zone every 3 months for 2 years. Expanding-focus surveillance is the only way to catch missed cases.
  </Step>
</Steps>

## Recommended alert settings

| Trigger                       | Condition                                                         | Severity  |
| ----------------------------- | ----------------------------------------------------------------- | --------- |
| Expanding cluster (satellite) | Localized NDVI decline expanding > 1 tree per month               | High      |
| Scout confirmation            | White rhizomorphs recorded on any tree                            | Critical  |
| Boundary sweep                | Automatic quarterly reminder for old-stump lines and forest edges | Automatic |
| Follow-up inspection          | 3-month cadence for 2 years after any confirmed case              | Automatic |

## Related

* [Red root disease](/guides/Crop/Rubber/biotic/diseases/red-root)
* [Brown root disease](/guides/Crop/Rubber/biotic/diseases/brown-root)
* [Field Walk Protocol](/guides/Crop/Rubber/field-walk-protocol) (root-collar inspection sequence)
* [Rubber Diagnosis](/guides/Crop/Rubber/rubber-diagnosis)