Mango anthracnose is a destructive fungal disease that poses the greatest threat to mango production globally. This ailment is caused primarily by the fungus Colletotrichum gloeosporioides, which affects the tree throughout its life cycle, both in the field and after harvest. The disease is highly prevalent in tropical and subtropical areas where high humidity and frequent rainfall create ideal conditions for fungal growth. Uncontrolled, mango anthracnose can lead to yield losses ranging from 30 to 60 percent, and in severe cases, nearly 100 percent of the fruit crop. The fungus also significantly reduces the quality and shelf-life of harvested fruit, directly impacting marketability and export standards.
Identifying Anthracnose Symptoms and Spread
Anthracnose manifests with symptoms across all above-ground parts of the mango tree, including leaves, flowers, and fruit. On young leaves, the infection first appears as small, angular, dark brown to black spots, which can enlarge and coalesce into larger necrotic areas. Flowers, or panicles, are particularly vulnerable, often developing small black or dark-brown spots that quickly expand, leading to blossom blight and the death of individual flowers or the entire cluster. This infection can drastically reduce fruit set, limiting overall yield.
The most recognizable sign of anthracnose is on the fruit, where it causes dark, sunken lesions that can develop into a characteristic “tear-stain” pattern as spores wash down the fruit surface. Importantly, the fungus often infects young, green fruit, where it remains dormant until the fruit begins to ripen after harvest. This latency means a fruit may appear healthy when picked but develop severe symptoms during transit or storage. Spore dispersal is favored by warm temperatures, typically between 25°C to 30°C, combined with high humidity and rain, which splash the conidia from existing lesions to new tissues, perpetuating the disease cycle.
Non-Chemical Management and Prevention
Effective control of mango anthracnose begins with cultural practices that reduce the environment’s favorability for the fungus. Canopy management is a primary strategy, involving yearly pruning to open the tree structure. This practice increases light penetration and, more importantly, air circulation, which helps dry out wet tissues quickly and discourages spore germination. Removing excessive foliage prevents the retention of moisture.
Water management can also limit disease spread. Overhead irrigation, especially during the critical flowering and fruit-setting periods, should be avoided, as it provides the necessary moisture for spore dispersal and infection. Sanitation is also foundational, requiring the prompt removal and destruction of all fallen plant debris, infected leaves, twigs, and mummified fruits from the orchard floor. These materials harbor the fungus and serve as a source of inoculum for new infections.
Wider plant spacing in new orchards can also inhibit severe epidemics by further improving air flow between trees. Furthermore, planting moderately resistant mango cultivars, such as ‘Keitt’ or ‘Tommy Atkins,’ can significantly lower the overall disease pressure compared to highly susceptible varieties. These non-chemical methods work synergistically to lower the fungal population before chemical intervention becomes necessary.
Fungicide Application and Timing
Chemical control through fungicides remains a highly effective and often necessary part of a comprehensive management program, especially in humid environments. The success of this strategy hinges entirely on correct application timing, which must be preventative to protect vulnerable new growth. Fungicide applications must begin when the flower panicles first emerge and continue at regular intervals until the fruit reaches a diameter of 1.5 to 2 inches.
Copper-based fungicides, such as copper hydroxide or copper sulfate, are widely used and serve as contact protectants against the disease. These are often rotated or combined with systemic fungicides, which are absorbed by the plant and offer a broader range of control. Systemic options include triazoles (like prochloraz) or strobilurins (such as azoxystrobin), which are highly effective against Colletotrichum gloeosporioides.
The application frequency typically ranges from weekly to bi-weekly, depending on environmental conditions, such as rainfall and humidity. Crucially, growers must rotate between different chemical classes, or modes of action, throughout the season to prevent the fungus from developing fungicide resistance. For instance, benzimidazole and strobilurin fungicides should be used sparingly to preserve their effectiveness. This rotation strategy ensures the fungal population remains sensitive to available chemical treatments.
Post-Harvest Disease Mitigation
Once mangoes are harvested, the focus shifts to preventing the development of latent infections. Post-harvest treatments are performed before the fruit is shipped or stored to maintain market quality. The most common and effective method to stop latent anthracnose is the hot water treatment (HWT).
For this treatment, fruits are fully submerged in hot water, typically at 52°C, for 15 minutes. This heat exposure is sufficient to kill the dormant fungal mycelium without damaging the fruit flesh. The effectiveness of the hot water dip can be increased by adding a post-harvest fungicide, such as thiabendazole or carbendazim, to the water bath.
Following treatment, proper storage conditions further slow fungal development. Storing the fruit at cool temperatures, generally between 10°C to 13°C, slows the ripening process, which in turn delays the onset of anthracnose symptoms. However, the temperature must be carefully controlled, as storing mangoes below this range risks chilling injury, which can compromise fruit quality. Additionally, careful handling during harvest and packing is necessary to minimize physical damage, as wounds can serve as entry points for infection.