Nalanthamala guava rot

The causative agent of this disease is the fungus Nalanthamala psidii, which belongs to the order Hypocreales. This pathogen is known for causing severe vascular distress and cortical necrosis in susceptible woody hosts. It is categorized as a systemic fungal disease that disrupts the nutrient and water transport mechanisms of the plant.

The primary host for this pathogen is the guava tree (Psidium guajava). This disease poses a significant challenge for guava production, particularly in tropical regions where climatic conditions are conducive to fungal growth. The impact is often cumulative, leading to the gradual decline of entire orchards if not managed effectively.

Symptoms typically manifest as necrotic lesions on the bark, which may eventually expand into deep cankers. Foliage on infected branches often shows signs of chlorosis followed by wilting and premature abscission. Internally, the woody tissue of affected branches exhibits discoloration, indicating that the fungal mycelium has colonized the vascular bundles of the plant.

Environmental conditions such as high humidity and frequent rainfall are critical for the development and spread of Nalanthamala psidii. The spores are primarily dispersed via wind, rain splash, and movement of contaminated pruning tools. Insect activity, which causes bark damage, serves as a common vector, facilitating the entry of the fungus into the tree’s internal tissues.

Management of this pathogen requires a proactive approach centered on orchard hygiene and chemical control. Effective protection measures include:

• Rigorous sanitation, including the removal and destruction of all infected branches.
• Disinfecting pruning tools with appropriate solutions to prevent cross-contamination.
• Application of copper-based or systemic fungicides during the early stages of disease progression.
• Implementation of proper pruning practices to improve canopy airflow and reduce moisture retention.