Anthracnose (Colletotrichum johnstonii)

The causal agent of this plant disease is the fungus Colletotrichum johnstonii. It is a well-known member of the genus Colletotrichum, widely recognized for causing anthracnose symptoms on various plant tissues, significantly impacting agricultural and horticultural productivity through tissue necrosis.

The host range of Colletotrichum johnstonii is extensive, including tropical and subtropical fruit-bearing plants, as well as various greenhouse crops. The pathogen infects plants at different growth stages, often colonizing leaves, stems, and fruits, which leads to substantial agricultural losses if left unmanaged.

Infection symptoms usually appear as small, water-soaked spots on foliage and fruit, which gradually enlarge and turn dark brown or black. As the disease progresses, acervuli—specialized fungal structures containing spores—become visible on the necrotic surface, especially under humid conditions, causing the characteristic sunken lesions associated with anthracnose.

Environmental conditions play a critical role in the life cycle of this pathogen. Warm temperatures, typically ranging from 20°C to 28°C, combined with high humidity or frequent rainfall, create ideal conditions for spore germination and rapid mycelial colonization. Free water on the plant surface is essential for the initiation of infection.

Effective management and disease control require an integrated approach. Key strategies include:

• Implementing strict sanitation practices to remove inoculum sources;
• Improving canopy aeration to reduce leaf wetness;
• Applying fungicides, particularly during wet weather periods;
• Selecting disease-resistant cultivars whenever available;
• Monitoring the field regularly to detect early signs of infection.