Collar rot is a serious disease caused by soil-borne fungi that attack the base of rubber trees, particularly in humid, cool weather conditions. If left untreated, the disease can kill young and mature trees alike, leading to significant production losses in Vietnam’s northern and central plantations.
1. Causal Agent and Distribution
Table of Contents
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Pathogens: Pythium spp. combined with Phytophthora spp.
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Distribution: Frequently occurs during prolonged rainy periods with high humidity and low temperature.
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Recently detected in northern mountainous provinces of Vietnam, where cool, moist soil conditions favor fungal development.
2. Damage and Economic Impact
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The disease attacks the collar region (0–10 cm above the soil surface), destroying the bark and phloem.
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Severe infections cause decay, girdling, and tree death.
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The damaged bark also creates entry points for secondary pathogens, worsening the infection.
3. Symptoms
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Initial symptoms appear as slightly sunken lesions with latex exudation around the collar zone.
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Under favorable (wet, cool) conditions:
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Lesions expand and darken.
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The bark becomes black, soft, and foul-smelling.
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Eventually, the bark rots away, exposing the wood beneath.
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Once the collar is fully girdled, the tree stops growing and dies.
(See Figure IX.12)
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4. Control and Treatment
Preventive Measures
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Avoid creating mechanical wounds near the collar during weeding, fertilizing, or hoeing.
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Conduct early inspections to detect diseased trees promptly.
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Mark infected trees for targeted treatment.
Curative Treatment
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Remove the infected, decayed bark around lesions.
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Apply fungicide:
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Metalaxyl 0.35% (3,500 ppm) mixed with 1.0% adhesive, spray or brush evenly onto the wound.
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Allow the area to dry completely, then apply a thin layer of vaseline to seal the wound.
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Recheck after 25–30 days. If symptoms persist, repeat treatment.
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Suspend tapping of infected trees and resume only after full recovery.
5. Preventive Management Practices
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Maintain good soil drainage to avoid prolonged moisture accumulation.
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Use clean, disinfected tools when working around roots.
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Improve aeration and nutrient balance to strengthen root resistance.
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Apply preventive fungicides during long rainy periods, especially in low-lying or shaded plots.
Conclusion
Collar rot poses a growing threat to Vietnam’s northern and central rubber plantations.
Early detection, precise fungicide application, and careful handling around the collar zone are key to preventing irreversible damage and maintaining healthy latex production.