Colletotrichum cairnsense

Initial signs of the infection typically present as small, water-soaked, or necrotic spots that gradually expand and turn dark brown or black.

As the disease progresses, these lesions become sunken, forming typical anthracnose craters on leaves, stems, flowers, or developing fruits.

Under high humidity, masses of slimy conidia, often appearing as pink or orange spore pustules, become visible on the surface of the dead tissue.

Severe infection leads to leaf blight, blossom end rot, and premature fruit drop, which significantly damages the overall structural integrity of the plant.

The diseased areas eventually turn brittle and may crack, potentially causing the collapse of stems or branches if the infection reaches deep into the tissue.

The disease is caused by the fungus Colletotrichum cairnsense, which belongs to the genus Colletotrichum, well-known for causing various forms of anthracnose in plants worldwide.

This pathogen is an opportunistic invader capable of infecting different plant tissues through natural openings like stomata or by directly penetrating the epidermis.

The fungus produces asexual spores, known as conidia, within specialized structures called acervuli that develop beneath the plant tissue surface.

Dissemination primarily occurs via water splashes during rainfall or overhead irrigation, as well as by wind, insect vectors, and the movement of contaminated tools.

It can survive as dormant mycelium or spores in infected plant debris, soil, or even on the surface of seeds, acting as a persistent source of infection.

Colletotrichum cairnsense thrives in warm and wet environments, with high relative humidity (above 90%) being the most critical factor for disease development.

Leaf wetness is essential for spore germination and colonization; therefore, rainy weather or improper irrigation practices are major drivers of outbreaks.

The optimal temperature range for this pathogen typically falls between +20°C and +28°C, which often coincides with the peak growing season of many hosts.

Poor ventilation in greenhouses and dense plant spacing create a stagnant, humid microclimate that dramatically accelerates the spread of the fungus.

Prolonged periods of dew or foggy mornings also provide sufficient moisture for the pathogen to successfully infect susceptible host tissues.

The economic impact of this pathogen is significant, as it leads to substantial crop losses in both yield quantity and the commercial quality of fresh produce.

Fruits infected with anthracnose are highly perishable and prone to post-harvest decay, making them unsuitable for long-term storage or international trade.

By weakening the host plant, the disease reduces overall vigor, making the crop more susceptible to environmental stress and secondary pathogen infections.

In seedling stages, the fungus can cause damping-off or stem lesions, leading to stand loss and the need for costly replanting efforts in agricultural fields.

The pathogen's ability to remain in the soil makes management difficult, as subsequent seasons are at high risk of recurrence unless strict sanitation is practiced.

Effective management begins with the use of certified, disease-free seed and the application of fungicides for seed treatment to prevent early infection.

Sanitation practices, including the removal and destruction of crop residues after harvest, are vital to reducing the fungal inoculum levels in the soil.

Switching from overhead irrigation to drip irrigation systems helps maintain a drier canopy, which significantly limits spore dispersal and germination.

Regular applications of protective and systemic fungicides during the growing season are necessary to suppress the development of the pathogen.

• Implementing wide spacing to improve air circulation.
• Rotating crops with non-susceptible plant families.
• Regularly monitoring fields for the first signs of lesions.
• Pruning and destroying infected branches to prevent further spread.