To enhance latex yield and maintain long-term productivity in Vietnam’s rubber plantations, latex stimulation methods using ethephon and ethylene gas are widely applied under strict technical and safety regulations.
These guidelines ensure effective latex flow, tree health, and worker safety during the tapping process.
1. Approved Stimulant Types and Concentrations
Table of Contents
The only approved stimulant for latex production is ethephon (2-chloroethyl phosphonic acid).
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Concentration for Group I and II plantations: 2.5%.
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Concentration for Group III plantations or pre-timber harvest trees: 5%, or optionally 2.5%.
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When using 2.5%, the maximum frequency of application may increase up to 1.5 times compared to the 5% concentration.
2. Recommended Stimulation Periods
For regions with distinct wet and dry seasons
(Southeast region, Central Highlands): May, June, July, August, October, November, and December.
For other regions
(Central Coast, Northern mountainous areas): April, May, June, August, September, and October.
Important notes:
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Apply the stimulant 24–48 hours before the next tapping cut.
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Do not apply when the tapping panel is wet or rain is expected.
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Avoid application during drought, cold weather (<15°C), or leaf-shedding (winter) periods.
3. Methods of Latex Stimulation (Figure VIII.9)
a. Panel Application (Pa Method) – for upward-facing panels
Stir the stimulant thoroughly, then use a brush to apply a 1 cm-wide, thin, even layer on the regenerated bark adjacent to the tapping cut.
b. Lace Application (La Method) – for downward-facing panels
Apply a thin, even layer directly on the tapping cut surface.
If dried latex residue is thick, remove it before application.
c. Special Application Tools for High Panels
For trees tapped at high positions beyond reach, use a pump bottle connected to a brush via tubing. The La method still applies, though contact with regenerated bark is acceptable due to limited control.
Recommended tools: Brush size No.8 or improved brushes with 0.8 cm width.
4. Dosage and Application Frequency
| Tree Group | Tapping Age | Method | Dosage per Tree per Time | Minimum Interval |
|---|---|---|---|---|
| Group I | 1–5 years | Pa | 0.5–1 g | 3 weeks |
| Group I | 6–10 years | Pa | 0.75–1.5 g | 3 weeks |
| Group II–III | >10 years | Pa or La | 0.75–2 g | 3 weeks |
5. Eligibility for Latex Stimulation
Only apply stimulants to:
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Trees with normal growth and proper tapping technique.
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Do not apply to trees that are stunted, diseased, have dry panels, or too small in diameter.
6. Technical Monitoring and Control
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If the Dry Rubber Content (DRC) of the plantation is below 25%, stimulation must not be used.
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If the rate of dry panels exceeds:
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3% in Group I plantations, or
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10% in Group II plantations,
further stimulation should be suspended until recovery.
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7. Safety Regulations for Workers
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Avoid skin or eye contact with stimulants.
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If contact occurs: wash skin with soap and warm water, rinse eyes with clean water and seek medical attention immediately.
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Collect and dispose of used chemical containers properly.
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When applying to downward-facing panels, wear protective goggles.
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Do not eat, drink, or smoke during application.
8. Storage Guidelines for Stimulant Chemicals
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Keep in cool, shaded areas, away from direct sunlight.
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Strictly follow the expiry date indicated on the packaging.
9. Latex Stimulation Using Ethylene Gas
This advanced method applies ethylene gas (C₂H₄) directly to the tree’s bark tissue through small devices attached near the tapping cut.
Applicable Conditions
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Tree age: ≥15 years.
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Good canopy, no major disease.
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Trunk circumference at 1.0 m height: >60 cm.
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Over 70% of trees in the plot must meet technical standards.
Not applicable for:
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Plantations with d₂ tapping frequency.
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Trees with depleted bark, poor latex yield, or non-standard tapping practices.
Harvesting Regimes
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S/6U d3 6d/7 10m/12 ETG G/3
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S/4U d3 6d/7 10m/12 ETG G/3
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Where labor is limited:
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d4 tapping (once every 4 days): inject ethylene every 3 tappings.
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d5–d6 tapping: inject ethylene every 2 tappings.
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Conclusion
Applying latex stimulants according to Vietnam’s technical standards ensures higher yield, tree longevity, and sustainable production.
Strict adherence to dosage, timing, and safety procedures protects both workers and plantations from potential damage while improving economic efficiency.