Anthracnose

Colletotrichum boninense is a pathogenic fungus belonging to the Colletotrichum gloeosporioides complex, responsible for causing anthracnose across a wide variety of plant species. This pathogen is known for its ability to infect both tropical and temperate crops, affecting leaves, stems, flowers, and fruits. As a necrotrophic fungus, it secretes enzymes that break down plant cell walls, leading to rapid tissue death and nutrient extraction.

The primary symptoms of the disease appear as dark, sunken, water-soaked lesions on the infected plant surfaces. As the infection progresses, these lesions often develop acervuli — small, spore-bearing structures that rupture the plant epidermis. Under humid conditions, these structures release masses of spores, typically colored pink, cream, or orange, which are easily visible to the naked eye or with a magnifying glass.

Environmental conditions play a critical role in the development and spread of Colletotrichum boninense. The fungus thrives in warm temperatures, typically ranging from +20°C to +30°C, combined with high humidity levels. Rainfall, splashing water from irrigation, and humid greenhouse environments are the primary catalysts for spore dispersal. The pathogen can also overwinter in soil debris, infected seeds, or on asymptomatic host plants.

The economic impact of this disease is significant, as it leads to severe crop losses, particularly in high-value fruits and vegetables. Infections occurring in the field often go unnoticed until harvest, only for the symptoms to manifest during storage and transport (post-harvest decay). This can result in the complete loss of marketability and total disposal of infected produce, causing significant financial strain on agricultural enterprises.

Managing Colletotrichum boninense requires an integrated pest management (IPM) approach:

• Selection of resistant or tolerant cultivars suitable for local climate conditions.
• Strict sanitation practices, including the removal and destruction of diseased plant parts.
• Implementation of drip irrigation to keep foliage and fruits dry and reduce spore splash.
• Application of appropriate fungicides, such as those containing azoles or strobilurins, based on disease forecasts.
• Rotation of crops to break the life cycle of the soil-borne inoculum.