Guignardia mangiferae

The fungus presents two distinct stages: the sexual stage (teleomorph), which produces pseudothecia, and the asexual stage (anamorph), known as Phyllosticta capitalensis, which produces conidia within pycnidia.

Microscopic identification is based on the observation of pycnidia, which appear as small, dark, flask-shaped structures embedded in the host tissue, containing hyaline, unicellular conidia.

When cultured on agar media, the fungus typically produces colonies with a variable appearance, ranging from white to dark grey, often forming a dense mycelial mat.

The pathogen is highly versatile and capable of surviving as a latent infection within healthy-looking plant tissues, making its detection challenging before visible symptoms appear.

While the primary host is mango (Mangifera indica), the fungus is known to infect a diverse range of tropical and subtropical plants, including coffee and various ornamental species.

In mango orchards, the pathogen affects leaves, shoots, inflorescences, and fruits. This leads to reduced yield and significant losses in the quality of the harvested produce.

Fruit infection is particularly devastating, as it results in necrotic lesions that promote secondary rots, rendering the fruits unmarketable for fresh consumption or export.

Infection of the inflorescences often causes blossom blight and fruit drop, which directly impacts the economic performance of the agricultural enterprise.

Chronic infections weaken the overall vigor of the trees, making them more susceptible to environmental stressors and other competing pests or diseases.

Initial symptoms are characterized by small, circular leaf spots that gradually expand, often displaying a brown or greyish center with a darker, well-defined margin.

The presence of minute black pycnidia scattered across the surface of the lesions is a hallmark sign, often visible to the naked eye or with a hand lens during advanced stages.

Fruit symptoms manifest as dark, sunken spots that may expand rapidly under humid conditions, often leading to total decay of the fruit tissue during the post-harvest period.

Young shoots may show elongated necrotic lesions or cankers, which, if left unchecked, can lead to dieback and the death of terminal branches.

Significant defoliation can occur during periods of high humidity and rainfall, as the fungus aggressively colonizes the weakened leaf tissue, causing premature leaf senescence.

Effective management begins with strict sanitation, including the regular removal and destruction of infected twigs, leaves, and fallen fruit that serve as primary sources of inoculum.

Canopy management, such as pruning to improve airflow and sunlight penetration, is crucial for reducing the humidity levels that the fungus requires for spore germination and colonization.

Chemical control strategies involve the use of protective copper-based fungicides or systemic compounds, applied systematically during key developmental stages like flowering and fruit set.

It is essential to implement an integrated pest management (IPM) program that includes rotating fungicides with different modes of action to prevent the development of resistant strains.

• Regular orchard scouting and monitoring for early symptoms.
• Balancing nutrient applications to promote plant health and stress tolerance.
• Sourcing certified, disease-free planting material to prevent pathogen introduction.