RUBBER NEWS

Botryodiplodia Disease in Vietnam’s Rubber Plantations

Posted on by content02.vinahugo
13
Oct

Botryodiplodia disease, caused by the fungus Botryodiplodia theobromae (Pat.), is one of the most destructive stem and bark diseases in Vietnam’s rubber plantations. It attacks trees at almost every growth stage, causing dieback, bark cracking, and latex yield loss if not treated promptly.

1. Causal Agent and Distribution

  • Pathogen: Botryodiplodia theobromae Pat.

  • Distribution: Widespread across Vietnam’s rubber-growing regions. The fungus is active mainly during the rainy season, and under unfavorable conditions, it survives in dormant sclerotial form.

  • Transmission: The disease spreads through spores and mycelia, mainly via humidity, rain splash, and wind.

  • The fungus is polyphagous, infecting nearly 500 plant species, especially woody trees.

2. Damage and Economic Impact

  • Causes low graft survival rates, seedling mortality, and slow growth.

  • Severe infection (grade 4 or higher) can reduce latex yield by 20–30% in commercial plantations.

  • Chronic infection leads to complete bark dryness and death of tapping panels.

3. Symptoms

In nurseries and budding stock (rootstock stage):

  • Small wart-like spots appear on the graft base, merging to form rough, resin-poor bark that is difficult to peel for budding.

  • At the bud union, infection during band removal causes bud death or dieback.
    (See Figure IX.8a–b)

In young plants and replanting fields:

  • Dark, sunken lesions appear on shoots; later, the entire shoot dries up.

  • Dead bark develops black dots containing spores.

  • Wood beneath the bark turns white with brown streaks; dead bark becomes tough and adheres to the wood.
    (Figure IX.8c)

In immature trees (1–2 years old):

  • Diamond-shaped cracks appear on brown-green bark, with latex exudation that later turns black.

  • The infected bark and wood become dry and brittle; leaves wilt but remain attached.

  • Lesions may spread along the stem, especially during the seasonal transition between dry and wet periods.

  • Usually found in clusters of 10–15 trees per plot.

In mature and commercial plantations (≥3 years old):

  • Small 1–2 mm nodules appear, later merging into clusters of 4–5 cm² or larger.

  • The bark surface becomes thick, rough, and scaly; cracks develop and may ooze latex.

  • In advanced stages, the fungus invades the cambium, causing bark rot, tissue death, and significant latex reduction.
    (Figures IX.8d–f)

4. Diagnosis and Differentiation

To ensure proper treatment, differentiate Botryodiplodia from non-pathogenic bark cracking caused by:

  • Physiological dryness, sun scorch, lightning, frost damage, or prolonged drought.
    Accurate identification prevents misuse of fungicides and allows timely management.

5. Control and Treatment

Only spray during the rainy season, and treat when more than 50% of trees are infected at grade 2 or above.
Severe cases (grade 4 or higher) require immediate intervention.

a. Nurseries and Budwood Gardens

  • Spray fungicides:

    • Hexaconazole 0.015% (150 ppm)

    • Tebuconazole 0.0375% (375 ppm)

    • Pyraclostrobin 0.0075% (75 ppm)

  • Add 0.3% adhesive, apply 2–3 times, 10–15 days apart.

  • Ensure seedlings are disease-free before planting.

b. Immature Plantations (1–2 years old)

  • Use one of the following:

    • Hexaconazole 0.015–0.025% (150–250 ppm)

    • Tebuconazole 0.05% (500 ppm)

    • Pyraclostrobin 0.01% (100 ppm)

  • Add 0.5% adhesive, apply 2–3 times, every 10–15 days.

  • For dead shoots, cut diagonally (45°), 10–20 cm below the lesion, and apply a thin layer of vaseline on the cut.

c. Mature and Commercial Plantations

  • Spray Hexaconazole 0.025% (250 ppm) + adhesive 0.5–1.0%.

  • Apply 2–3 times at 10–15 day intervals.

  • Cover the entire lesion area (0–3 m above the base).

  • Stop tapping severely infected trees until recovery.

6. Preventive Measures

  • Use healthy planting material from certified nurseries.

  • Avoid waterlogging and mechanical injuries on trunks.

  • Conduct regular inspections, especially during humid months.

  • Disinfect cutting tools frequently to prevent fungal spread.

Conclusion

Botryodiplodia disease is a major fungal threat to Vietnam’s rubber plantations.
Early detection, preventive fungicide spraying, and good field hygiene are critical to maintaining healthy trees and stable latex yield.