Powdery mildew of rubber tree

The causative agent of this disease is the fungus Oidium heveae, a specialized plant pathogen that triggers powdery mildew infections. It primarily targets the tender foliage of host plants, hindering their development and photosynthetic capacity by forming a dense mycelial mat on the leaf surfaces.

The primary host for this pathogen is the rubber tree (Hevea brasiliensis), which is economically significant due to its role in natural rubber production. The disease poses a constant threat to rubber plantations worldwide, specifically in regions where climatic conditions favor the survival and spread of the fungal spores during the tree's refoliation phase.

Symptoms of the infection manifest as small, white, powdery patches on the underside of young, tender leaves. As the disease progresses, the mycelium spreads to the upper surface, causing leaves to curl, distort, and eventually turn brown and wither. Severe infestations lead to premature leaf fall, which significantly depletes the tree's physiological reserves.

The development of Oidium heveae is highly dependent on environmental conditions, particularly high relative humidity and moderate temperatures. Spores are primarily wind-dispersed, allowing the fungus to spread rapidly across plantation plots. Dense planting and lack of air circulation within the canopy exacerbate the disease spread during the critical period of leaf flushing.

Effective management of powdery mildew requires an integrated strategy to minimize yield losses. Since the disease impacts the canopy and thus the overall health of the rubber tree, producers prioritize the selection of resistant clones. When chemical intervention is necessary, the following practices are typically employed:

• Application of sulfur-based fungicides to inhibit fungal growth.
• Monitoring plantation health specifically during the annual wintering and refoliation cycles.
• Maintaining proper plantation spacing to ensure optimal air movement.
• Implementing sanitary measures to remove heavily infected plant debris where possible.