Mango macrophoma rot

Symptoms typically begin as small, scattered brownish spots on the leaves. Over time, these spots enlarge, turn necrotic, and may develop a gray or dark center.

On woody stems and branches, the infection causes bark cracking and cankers. Small, black, pinhead-sized structures (pycnidia) often emerge from these damaged areas.

Dieback of young shoots is a classic sign of the disease, leading to a stunted appearance of the branch tips and subsequent foliage loss.

On mature fruits, the disease manifests as dark, sunken, circular lesions. These spots can coalesce, leading to severe fruit decay and rendering the product unmarketable.

• brown, enlarging leaf lesions;
• cracking bark and cankers on branches;
• visible black fruiting bodies (pycnidia);
• withered shoots and premature fruit drop.

The disease is caused by the fungus Macrophoma mangiferae, a pathogen that specifically targets mango trees. It belongs to the coelomycete group, known for producing spores within specialized structures called pycnidia.

This fungus acts as a latent pathogen, surviving in dead twigs, bark, and fallen leaves during the off-season. It remains dormant until environmental conditions allow it to re-emerge.

Transmission occurs through the dispersal of spores by rain splashes, wind currents, and contaminated orchard tools. Once on the host surface, the fungus uses specialized enzymes to penetrate tissues.

The life cycle of the pathogen is closely tied to humidity levels. Increased moisture allows the fungus to form new pycnidia, which release thousands of spores into the orchard environment.

As a parasitic agent, it effectively exploits the host's weakened tissues, gradually expanding the area of necrosis across the tree's branches and fruits.

High relative humidity, typically exceeding 80–90%, is the primary factor driving the development and spread of Mango Macrophoma rot in tropical regions.

Warm temperatures ranging between +24°C and +28°C provide the optimal thermal range for the fungus to grow and colonize the mango tree tissues efficiently.

Orchards with poor canopy management often experience severe outbreaks because dense foliage traps moisture, creating a perfect incubation chamber for the spores.

Prolonged wetness on the tree surface after rain events facilitates the germination of fungal spores and the subsequent infection of healthy plant tissues.

Host stress, whether from nutrient deficiency or drought followed by heavy rainfall, significantly increases the tree's susceptibility to the fungal pathogen.

The economic impact of Macrophoma rot is significant, as it directly reduces fruit yield and compromises the quality of the harvested produce for export markets.

Chronic infections weaken the overall vigor of the mango tree, leading to stunted vegetative growth and reduced potential for fruit production in following seasons.

The damage caused to branches requires intensive pruning, which can permanently alter the structure of the tree and reduce its lifespan if left unmanaged.

Fruits affected by this rot are highly perishable. Secondary infections often infiltrate the necrotic spots, causing complete decay during post-harvest storage.

Orchard maintenance costs rise significantly when growers must implement strict chemical and cultural control programs to manage the persistent fungal population.

The most effective strategy involves strict sanitation measures, such as the prompt removal and burning of infected branches and fruits to reduce the inoculum load.

Regular applications of copper-based fungicides during the pre-flowering and fruit-set stages are essential to prevent the fungus from establishing a foothold.

Implementing proper canopy pruning ensures adequate airflow and light penetration, which naturally dries the foliage and reduces the risk of fungal colonization.

Balanced fertilization and good irrigation management help maintain the tree's health, allowing it to withstand environmental stress and resist fungal attacks.

Sterilizing pruning tools between trees is a mandatory practice to prevent the cross-contamination of the fungus throughout the mango orchard.