Rubber trees are highly sensitive to environmental changes and fungal infections.
Stem and branch diseases can significantly reduce latex yield, deform tree canopies, and even lead to total tree death if not managed promptly.
This section covers two of the most common diseases affecting rubber stems and branches in Vietnam: Dieback and Pink Disease.
1. Dieback
Table of Contents
Causal Factors
Dieback in rubber trees can result from both biological and environmental causes:
-
Pathogenic causes: Secondary infections from Corynespora, powdery mildew, anthracnose, rainy-season leaf fall, Botryodiplodia, or scale insects.
-
Environmental stress: Strong winds, cold spells, drought, lightning strikes, nutrient deficiencies, or waterlogging.
Damage
-
Causes dieback of shoots and branches in nurseries, young plantations (immature trees), and even mature commercial plantations.
-
In severe cases, it can lead to partial or complete canopy death.
Treatment
-
Identify the cause and apply appropriate corrective measures:
-
Fertilization to restore nutrition.
-
Protection against cold and drought.
-
Timely control of leaf diseases and pests.
-
-
For infected trees or branches:
-
Cut the branch diagonally (45°), 10–20 cm below the dead section.
-
Apply a thin layer of vaseline on the cut surface to prevent reinfection.
-
2. Pink Disease
Causal Agent
-
Caused by the fungus Corticium salmonicolor Berk. & Br.
Distribution
-
Common in areas with distinct dry and rainy seasons at altitudes below 300 m.
-
The disease is most severe during the rainy season.
Damage
-
Affects trees aged 3–12 years, most severe between 4–8 years old.
-
Causes branch dieback and terminal shoot death, leading to loss of canopy and productivity.
Symptoms
-
Appears on brown, matured bark of stems and branches.
-
Early stage: thin white fungal threads resembling a spider web with slight latex exudation.
-
Advanced stage: mycelium turns pink, latex exudes heavily, and lesions expand.
-
Dead branches retain dry leaves, and new shoots sprout below the infection site.
(See Figure IX.7)
Treatment
-
Early detection is crucial for effective control.
-
Spray one of the following fungicides:
-
Validamycin 0.060–0.075 % (600–750 ppm), or
-
Hexaconazole 0.025 % (250 ppm),
-
plus 1.0 % adhesive solution.
-
-
Apply until surfaces are thoroughly wet, covering 20 cm above and 10 cm below the lesion.
-
Repeat every 10–14 days until symptoms disappear.
-
Mark and recheck treated trees for any signs of recurrence.
-
Suspend tapping on severely infected or dead-canopy trees.
-
During the dry season, cut and remove all dead branches and trees to the plot edge for disposal.
Conclusion
Effective management of stem and branch diseases such as Dieback and Pink Disease is essential for maintaining healthy rubber plantations and preventing latex yield loss.
Early detection, regular inspection, and strict field sanitation play a decisive role in minimizing infection spread.