Mango anthracnose is a significant fungal disease affecting mango production worldwide. It is caused by the fungus Colletotrichum gloeosporioides, a pathogen that thrives in wet, humid conditions. The fungus spreads through airborne spores dispersed by rain, making it particularly destructive during the mango’s flowering and fruiting seasons. This disease can impact the leaves, flowers, and fruit, leading to substantial crop losses if not properly managed.
Identifying Mango Anthracnose Symptoms
On leaves, the disease appears as small, angular, or irregularly shaped black or brown spots. These spots often appear near the leaf margins and can be surrounded by a darker border. During high humidity, these lesions can enlarge and merge, causing significant leaf blight or making the affected tissue drop out, leaving holes in the leaves.
The impact on flowers is particularly damaging to fruit production. Infection begins as small, dark brown or black spots on the flower panicles that quickly expand and merge. This kills the individual flowers, a condition known as blossom blight, which prevents the tree from setting fruit and drastically reduces yield. The entire infected panicle can wither and die.
The most common symptom on fruit is the appearance of dark, sunken, circular spots on the skin of ripening mangoes. These spots can enlarge and merge, and under humid conditions, may produce pink or salmon-colored spore masses in their centers. These infections often remain dormant in green fruit and only become active as it ripens, leading to significant rot during storage.
Cultural and Physical Control Methods
Managing mango anthracnose relies on cultural practices that create an environment less favorable for the fungus. Strategic pruning is a primary technique that removes branches to open up the tree’s canopy. This increased airflow and sunlight helps dry leaves and flowers more quickly, reducing the moist conditions the fungus needs. Pruning also removes infected twigs that can harbor the pathogen.
Orchard sanitation is another practice for reducing the source of fungal spores. This involves collecting and destroying fallen leaves, twigs, and rotted fruit from the ground around the trees. These materials can serve as a reservoir for the fungus, allowing it to survive between seasons and re-infect the tree. Removing this debris significantly lowers the amount of inoculum in the orchard.
Proper water management helps limit the spread of fungal spores, which are dispersed by water splash. Avoid overhead irrigation that wets the tree canopy and instead direct water to the base of the tree. This minimizes leaf wetness and reduces opportunities for infection. Ensuring adequate spacing between trees also promotes better air circulation and reduces humidity.
Chemical Fungicide Applications
In climates with high humidity, cultural controls alone may not be sufficient, necessitating the use of chemical fungicides. These treatments are most effective as a preventative measure rather than a cure. Fungicides are categorized as either protectants, which form a barrier on the plant surface, or systemics, which are absorbed into the plant’s tissues. Copper-based fungicides and mancozeb are common protectants.
The timing of fungicide applications determines their success. Spraying should begin before flowers open and continue at regular intervals through fruit development, especially during wet weather. This preventative schedule protects the susceptible flowers and young fruit from infection. The frequency of application depends on the fungicide, weather, and disease pressure.
Consult local agricultural extension services for recommendations on effective and legally registered fungicides for your region. Always read and strictly adhere to the product label instructions for application rates, timing, and safety precautions. This ensures the treatment is effective and safe for the applicator, consumers, and the environment.
Post-Harvest Fruit Treatments
Even with diligent orchard management, mangoes can harbor latent infections at harvest. These infections develop into visible rot as the fruit ripens. To manage this and extend shelf life, specific post-harvest treatments are employed, particularly in commercial operations.
The most common post-harvest method is Hot Water Treatment (HWT). This process involves immersing harvested mangoes in a hot water bath maintained at a precise temperature, 50-55°C (122-131°F), for 5 to 10 minutes. This is sufficient to kill fungal spores on and just beneath the skin of the fruit without cooking the flesh.
This treatment effectively manages anthracnose and other post-harvest diseases like stem-end rot. It is a standard in the commercial mango industry because it reduces decay during shipping and ripening. By controlling latent infections, HWT ensures a higher quality product reaches the consumer with a longer shelf life. Some operations also use post-harvest fungicide dips to control rot.