RUBBER NEWS

Identifying and Controlling Powdery Mildew on Rubber Trees

Posted on by content02.vinahugo
12
Oct

Powdery mildew is a major foliar disease that seriously affects rubber trees, especially in susceptible varieties and during the tapping stage. Early detection and proper management are essential to prevent severe yield losses.

1. When Does Powdery Mildew Occur?

Powdery mildew typically appears from January to March, coinciding with the leaf-shedding and refoliation periodof rubber trees.

During this time, young leaves (1–10 days old) are highly susceptible. The disease spreads quickly in cool, foggy, and humid conditions, which favor fungal development.

2. Symptoms of Powdery Mildew Infection

  • When infection occurs during the early leaf stage, leaves tend to fall prematurely, forcing the tree to re-grow new leaves, which weakens it and delays tapping operations.

  • If infection occurs after 10 days of leaf age, leaves do not fall but become distorted, with irregular pale yellow or brown patches.

  • The affected leaves have lower chlorophyll content, resulting in reduced photosynthesis and ultimately lower latex yields.

(Illustration: powdery mildew on rubber leaves)

3. Causal Agent

The disease is caused by the fungus Oidium heveae Steinm., also known as Acrosporium heveae (Steinm.) Subramanian.

The fungus produces white mycelium threads and spores, giving infected leaves a characteristic powdery white coating, hence the name powdery mildew.

4. Preventive and Control Measures

As with most plant diseases, prevention is more effective than treatment.
For rubber trees, the following measures are recommended:

Agronomic Measures

  • Apply fertilizers properly, especially nitrogen and potassium at the end of the rainy season to strengthen new shoots and reduce susceptibility.

  • Avoid over-tapping or excessive latex extraction to prevent weakening trees.

  • Plant disease-tolerant varieties, such as RRIV 103, RRIV 115, and RRIV 209, based on regional recommendations.

  • Spray preventive fungicides before the expected disease period.

5. Common Fungicides Used for Control

(a) Anvil 5SC

  • Active ingredient: Hexaconazole 50 g/L

  • Dosage: 0.2% solution (mix with 0.2% BDNH 2000 sticking agent)

  • Application: Spray when 10–15% of trees have emerging leaves (bird-foot stage).

  • Frequency: 2–3 times, 10 days apart.

  • Note: Spray evenly during cool hours (early morning or late afternoon); avoid hot sunny periods.

  • Spray volume: 400–700 L/ha depending on canopy density.

(b) Vixazol 275SC

  • Active ingredients: Carbendazim + Hexaconazole

  • Dosage and method: Same as Anvil 5SC

  • Remarks: Provides both protective and curative action; ensure consistent spraying intervals.

(c) Sumi-Eight 12.5WP

  • Active ingredient: Diniconazole

  • Dosage: 0.05%–0.1% solution (plus 0.2% BDNH 2000)

  • Application: Similar schedule — 2 to 3 sprays every 10 days during leaf flushing.

  • Volume: 400–700 L/ha.

(d) Kumulus 80DF

  • Active ingredient: Micronized sulfur (80%)

  • Dosage: 0.3% solution (plus 0.2% BDNH 2000)

  • Application: Recommended for nurseries and young plantations.

    • Begin spraying when 10% of trees have new leaves.

    • Stop when 80% of leaves are fully expanded.

    • Spray 2–3 times at 7–10 day intervals.

    • Combine with foliar nutrients from the second application onwards.

6. Key Takeaways

  • Powdery mildew is a serious foliar disease that can significantly reduce latex yield.

  • Early prevention through proper fertilization, timely spraying, and resistant varieties is the best strategy.

  • Follow the recommended spray schedule, dosage, and weather conditions to ensure maximum effectiveness.