Colletotrichum makassarense

The primary symptom of infection is the development of necrotic lesions on leaves, stems, and fruits. These spots are typically circular or irregular in shape and are often surrounded by a chlorotic halo caused by the pathogen's toxins.

Under conditions of high humidity, a characteristic mass of conidial spores, known as a spore mass, appears on the surface of the lesions. The color of this mass ranges from whitish to pinkish or dark brown, depending on the developmental stage.

Affected tissues often become soft and sunken, forming deep ulcers. On fruit, this manifests as depressed spots that can merge, eventually covering large portions of the surface and leading to fruit decay.

Infection of stems often leads to the death of the upper portions, resembling a burn. The pathogen disrupts the plant's vascular system, causing the rapid loss of turgor pressure and eventual wilting of the affected parts of the plant.

Necrosis may also occur at the root collar or stem base, causing longitudinal cracking. This structural damage weakens the plant, making it significantly more susceptible to lodging and secondary infections.

The disease is caused by the microscopic ascomycete fungus Colletotrichum makassarense. This pathogen belongs to the Colletotrichum genus, which is globally recognized as the primary agent of anthracnose in various agricultural and horticultural crops.

The fungus is characterized by the production of specialized fruiting bodies known as acervuli, which contain numerous conidia. These spores serve as the main mechanism for the spread of the infection throughout the growing season.

Its biological cycle involves transitioning between a saprotrophic lifestyle on dead plant debris and an aggressive parasitic lifestyle on living tissues. This versatility allows the fungus to persist in agricultural environments for extended periods.

Research suggests this species is closely related to the Colletotrichum gloeosporioides species complex. It colonizes the intercellular spaces of host tissues, secreting enzymes that degrade cell walls to extract necessary nutrients for growth.

Accurate identification of this pathogen often requires laboratory-based molecular techniques, such as DNA sequencing of the ITS region, as morphological similarities to other Colletotrichum species can lead to misidentification.

The development of Colletotrichum makassarense is favored by warm temperatures (22–28°C) combined with prolonged high humidity. These conditions provide the perfect environment for spore germination and rapid mycelial growth.

Free water on plant surfaces, resulting from rainfall, dew, or fog, is essential for the dispersal of conidia. Rain splashes play a critical role in moving spores from infected plant parts to healthy tissues.

Poor ventilation and high-density planting create a stagnant microclimate that accelerates the spread of the infection. In such conditions, the disease can transition into an epidemic form very rapidly.

Mechanical damage, whether from insect feeding, hail, or agricultural operations, provides ideal entry points for the fungal hyphae. Stressed or nutrient-deficient plants are significantly less able to mount an effective defense against invasion.

The fungus can survive for several seasons in the soil or on crop residues. If sanitation practices are neglected, the field remains a source of primary inoculum for subsequent planting cycles.

The economic impact of the disease stems from a significant reduction in photosynthetic leaf area, which stunts plant growth and limits biomass accumulation. This results in direct yield losses.

Infected fruit and seeds exhibit poor quality, making them unsuitable for storage, transport, or market sale. The resulting decay often triggers secondary colonization by opportunistic bacteria, further damaging the harvest.

Due to the wide host range of the fungus, managing the disease through crop rotation is challenging. The pathogen's ability to persist in diverse environments complicates efforts to eliminate the threat from affected farms.

Rapid dispersal via wind and rain splashes means that the infection can spread across large fields in a very short time. Without timely intervention, total crop loss in localized areas is a significant risk.

In perennial crops, repeated infection weakens the plants, reducing their long-term productivity and overall vigor. This makes them more prone to winter injury and other abiotic stresses, potentially leading to stand death.

Effective management begins with strict agronomic practices, such as ensuring proper spacing to improve airflow and eliminating weeds that may act as alternative hosts for the pathogen.

Sanitation is crucial: all crop residues should be removed and destroyed after harvest. Deep plowing can help bury infected debris, accelerating decomposition and reducing the initial spore load in the following season.

Chemical control involving fungicides from classes such as strobilurins and triazoles is effective when applied preventatively, especially during periods of wet weather when infection risk is highest.

Using resistant varieties or hybrids is the most sustainable long-term solution. Breeding programs continue to prioritize the development of crops with enhanced immunity to Colletotrichum species.

• Implement a minimum 3-year crop rotation schedule.
• Use certified disease-free seeds or treated planting material.
• Regularly monitor fields for the earliest signs of lesions.
• Disinfect agricultural tools between uses to prevent cross-contamination.
• Maintain balanced soil fertility, avoiding excessive nitrogen applications.