Anthracnose

The initial signs of the disease are small, water-soaked spots that eventually darken and become sunken. Often, a yellow chlorotic halo appears around the edges of the affected areas.

In the center of the necrotic spots, under high humidity, concentric rings form, consisting of tiny cushions called acervuli. These structures are colored pink or salmon due to the mass of spores produced.

Infection can affect all aerial organs of the plant: leaves, stems, inflorescences, and fruits. On fruits, anthracnose manifests as deep ulcers that eventually lead to complete tissue decay.

When stems are affected, constriction occurs, causing wilting and death of the parts of the plant above the lesion. If severely infected, leaves dry out and fall prematurely, which drastically reduces productivity.

• Appearance of dark, sunken spots on fruits and leaves.
• Pinkish spore masses on necrosis sites during high humidity.
• Premature dropping of leaves and fruits.
• Deformation and drying out of individual branches or entire shoots.

The causal agent of this disease is the fungus Colletotrichum chiangraiense, which belongs to the genus Colletotrichum, family Glomerellaceae. It is an ascomycete that reproduces asexually by forming conidia in specialized structures called acervuli.

The fungus is highly aggressive and capable of infecting a wide range of crops, particularly tropical and subtropical plants, including chili peppers and other Solanaceae. The pathogen's mycelium penetrates deep into plant tissues, destroying cellular integrity.

The infection persists in plant debris, seeds, and soil as mycelium or sclerotia. The life cycle of the pathogen is closely tied to climatic factors, allowing for rapid spread during the growing season.

The genetic plasticity of Colletotrichum chiangraiense allows it to adapt to various environmental conditions, complicating the development of resistant cultivars. Experts note significant variability within the species, which influences the virulence of individual isolates.

Pathogen spores are spread primarily by rain splashes, wind currents, and contact with contaminated agricultural equipment. High humidity is a critical factor for the initiation of active sporulation.

The key condition for the mass spread of Colletotrichum chiangraiense is high relative humidity (above 85-90%). The fungus develops most actively during periods of prolonged rain or intense dew.

The optimal temperature range for the growth and development of the pathogen is between +22°C and +28°C. Deviations from these values slow down the pathogen's development, though it remains viable.

Poor agricultural practices, such as excessive overhead irrigation and dense planting, help create a microclimate favorable for infection. Poor ventilation in greenhouses significantly increases risks.

Unbalanced nutrition, particularly excess nitrogen fertilization, reduces the plant's natural resistance to infection. Tissues become softer and more vulnerable to the penetration of the pathogen's hyphae.

The presence of weeds in the field often acts as an infection reservoir, where the fungus can multiply before the growing season of the target crops begins.

The damage caused by anthracnose manifests in direct loss of commercial value, making produce unsuitable for sale or storage. Fruits infected by the pathogen rot quickly, even after harvest.

The disease causes a reduction in total yield by 30–80%, depending on the level of infection and weather conditions. This affects not only the quantity but also the quality of the harvested crop.

Severe infection of vegetative organs leads to a suppression of photosynthetic activity, which reflects on the overall growth of the plant. In neglected cases, total crop failure or the death of individual plants is possible.

Economic losses include costs for fungicide treatments, loss of commercial produce, and the need for labor-intensive phytosanitary measures in the field.

The pathogen is prone to latent infection, where external symptoms manifest only during transport or storage, which severely impacts the export potential of agricultural holdings.

Prevention starts with the use of healthy planting material. Seeds must undergo mandatory treatment with systemic fungicides to eliminate both surface and internal infection.

An important practice is crop rotation, which excludes the return of susceptible crops to an infected field for 2–3 years. It is necessary to promptly remove all plant residues after harvest.

During the growing season, it is recommended to conduct preventive sprays with contact fungicides, and at the first sign of disease, apply systemic products. It is important to rotate protection methods to prevent resistance development.

Organizing a proper irrigation regimen (drip irrigation is preferred over overhead watering) and ensuring good air circulation in greenhouses can significantly reduce the risk of an outbreak.

Timely weeding and pest control, which can mechanically damage plant tissues, are necessary components of an integrated system for controlling anthracnose.