Colletotrichum hainanense

Symptoms typically begin as small, water-soaked lesions on leaves or stems that rapidly expand into necrotic spots with dark margins.

The center of these lesions often develops acervuli, small fruiting bodies that release slimy masses of pink or cream-colored spores under humid conditions.

Fruit infection is characterized by sunken, dark-colored lesions that expand and become covered with characteristic spore masses, leading to post-harvest decay.

Stem cankers may occur, where lesions girdle the stem, causing wilting, stunting, and eventually the death of the entire plant or specific branches.

In seedling stages, the fungus causes damping-off, where the base of the stem turns black and shrivels, leading to the collapse of young plants.

The disease is caused by the fungus Colletotrichum hainanense, an ascomycete pathogen known for causing serious anthracnose-type infections in various crops.

This pathogen belongs to the Colletotrichum gloeosporioides species complex, making its precise identification difficult without molecular diagnostic methods.

The fungus produces masses of conidia that serve as the primary inoculum, spreading through rain splash, wind currents, and contaminated agricultural tools.

It acts as a hemibiotroph, initially colonizing living host tissues before switching to necrotrophic growth, which leads to tissue collapse and cell death.

Survival of the fungus is ensured by its ability to persist in soil organic matter, infected plant debris, and occasionally within or on the surface of seeds.

High relative humidity, typically exceeding 85%, is the most critical environmental factor triggering the germination and infection process of C. hainanense.

Warm temperatures ranging from +22°C to +28°C provide the optimal metabolic environment for the rapid expansion of fungal colonies and spore production.

Poor ventilation, particularly in greenhouses or densely planted fields, creates stagnant air conditions that favor the persistence of moisture on foliage.

Frequent rainfall episodes promote the dissemination of spores from the ground to the lower leaves, facilitating the upward spread of the disease.

Susceptibility is increased by plant stress, such as improper fertilization, lack of light, or physical wounds from insect feeding, which provide entry points for the fungus.

The primary economic impact is the direct reduction in yield quality, as fruits damaged by anthracnose are unsellable and prone to rapid secondary rotting.

Extensive leaf damage reduces the plant's photosynthetic capacity, resulting in lower sugar content in fruits and stunted overall growth.

Premature fruit drop and defoliation caused by severe infections can lead to a total loss of the harvest in highly susceptible varieties.

Seed-borne transmission poses a risk to future crops, potentially leading to poor germination rates and stunted plant development in subsequent cycles.

The necessity for frequent fungicide applications increases the cost of production and complicates integrated pest management (IPM) efforts.

Control strategies rely on a combination of cultural practices, such as crop rotation, and the strict removal of all infected plant residues after harvest.

Selecting and planting disease-free, certified seeds is the first line of defense to prevent introducing the pathogen into clean cultivation areas.

Application of fungicides, including copper-based products or systemic triazoles, should be timed with environmental forecasts to prevent infection outbreaks.

• Proper spacing to improve airflow and reduce humidity levels within the canopy.
• Sanitization of all equipment used in harvest and pruning to avoid cross-contamination.
• Balanced nutrition to strengthen plant cell walls and natural defense mechanisms.

Regular scouting of crops is essential to detect early symptoms, allowing for immediate surgical removal and local treatment of affected areas to stop spread.