> ## 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.

# Black Stripe (Panel Phytophthora) in Rubber

> Phytophthora palmivora / P. meadii on the tapping panel: how bad tapping technique and wet weather cause vertical black streaks that destroy the panel.

**Black stripe** (also called **black thread** or **panel Phytophthora**) is caused by *Phytophthora palmivora* or *P. meadii* attacking the tapping cut. Wet, warm weather combined with poor tapping cuts creates the entry point. Once established, vertical black streaks propagate down the panel, destroying the cambium and permanently reducing yield.

## Cause

* **Wet weather at tapping** (rain within hours of tapping)
* **Deep or ragged tapping cuts** (bark wounds beyond the cambium)
* **Dirty tapping knives** (pathogen spread from tree to tree)
* **Tapping in the early morning during wet season** (spore-rich conditions)
* **Poor panel hygiene** (mud splash, no wound protectant)

## Effect

| Stage    | Symptom                                                                          |
| -------- | -------------------------------------------------------------------------------- |
| Early    | Vertical dark streak (2 to 5 mm wide) below the tapping cut                      |
| Mid      | Streak lengthens (10 to 30 cm), sunken bark, latex exudes and dries as dark scab |
| Late     | Wide black patches, cambium destruction, bark cracks and falls off               |
| Terminal | Panel unusable, tree must be rested or panel switched to next segment            |

## Satellite signals

None. Black stripe is a tree-level disease diagnosed at the panel during tapping rounds.

## Action

<Steps>
  <Step title="Scout every tapping round">
    Tappers should visually inspect the panel below the cut on every round. Any vertical dark streak should be flagged immediately.
  </Step>

  <Step title="Suspend tapping on affected trees">
    Stop tapping the affected panel. Continued tapping spreads the pathogen down the panel and to neighboring trees via the knife.
  </Step>

  <Step title="Apply wound protectant fungicide">
    Paint the panel with **metalaxyl** (Ridomil) or **fosetyl-Al** paste around the cut. Repeat weekly for 4 weeks.
  </Step>

  <Step title="Sanitize tapping knives">
    Dip knives in fungicide or bleach between trees during outbreaks. Train tappers on proper cut technique.
  </Step>

  <Step title="Panel switch">
    On severely affected trees, rest the panel and switch to the next tapping panel segment at the next tapping cycle.
  </Step>

  <Step title="Prevent in wet season">
    Do not tap when trees are wet (rain within 4 hours). Prophylactic fungicide painting during monsoon on high-risk blocks.
  </Step>
</Steps>

## Recommended alert settings

| Trigger              | Condition                                               | Severity                           |
| -------------------- | ------------------------------------------------------- | ---------------------------------- |
| Scout report         | Any tree with vertical black streak on panel            | High                               |
| Cluster of cases     | > 3 trees in a block within 1 week                      | Critical (whole-block prophylaxis) |
| Wet-weather advisory | Rain > 50 mm/day during tapping season on tapped blocks | Medium                             |

## Related

* [Pink disease](/guides/Crop/Rubber/biotic/diseases/pink-disease)
* [Tapping Panel Dryness](/guides/Crop/Rubber/biotic/tpd)
* [Field Walk Protocol](/guides/Crop/Rubber/field-walk-protocol)